File size: 4,824 Bytes
32186fa | 1 | [{"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}] |