WEBVTT 00:00:03.062 --> 00:00:05.965 8 BIT PHILOSOPHY 00:00:06.740 --> 00:00:11.906 ♪ (fantasy music) ♪ 00:00:18.703 --> 00:00:20.966 Is change merely an illusion? 00:00:22.556 --> 00:00:24.825 In 5th Century BC, 00:00:24.825 --> 00:00:27.314 Greek philosopher Parmenides proposed 00:00:27.314 --> 00:00:30.235 that the universe was not made of many things, 00:00:31.145 --> 00:00:34.426 but rather is a single indivisible substance: 00:00:35.994 --> 00:00:39.015 An eternal now that encompasses all time 00:00:39.335 --> 00:00:40.582 and all entities. 00:00:42.286 --> 00:00:43.660 And if the universe is one, 00:00:43.910 --> 00:00:46.010 then all change is impossible. 00:00:46.210 --> 00:00:48.425 For the very idea of change suggests 00:00:48.425 --> 00:00:50.665 something transforming from one state 00:00:50.875 --> 00:00:51.914 to another. 00:00:51.914 --> 00:00:54.043 But according to Parmenides, 00:00:54.043 --> 00:00:56.664 all states occur simultaneously-- 00:00:56.664 --> 00:00:58.616 change is impossible. 00:01:00.636 --> 00:01:02.482 After receiving heavy criticism 00:01:02.482 --> 00:01:04.792 from his contemporaries, Parmenides' student, 00:01:04.792 --> 00:01:07.476 Zeno of Elea, came to his defense 00:01:07.476 --> 00:01:10.562 by creating a series of paradoxes that seek 00:01:10.562 --> 00:01:13.048 to prove that time and change are, 00:01:13.398 --> 00:01:15.971 in fact, utter nonsense. 00:01:16.028 --> 00:01:20.279 ♪ (Excitebike Theme Song) ♪ 00:01:26.133 --> 00:01:28.946 Consider a situation in which a motorcyclist 00:01:28.946 --> 00:01:30.393 races a man on foot. 00:01:30.603 --> 00:01:32.452 Let's assume the man is given 00:01:32.452 --> 00:01:34.629 a 50 meter head start. 00:01:34.629 --> 00:01:37.063 By the time the motorcyclist reaches 00:01:37.063 --> 00:01:39.496 the 50 meter mark, the man will have moved 00:01:39.496 --> 00:01:41.097 a small distance forward. 00:01:41.097 --> 00:01:42.906 And when the motorcyclist catches up 00:01:42.906 --> 00:01:45.434 to the ensuing spot, the man will have moved 00:01:45.434 --> 00:01:46.951 farther still. 00:01:47.041 --> 00:01:48.709 If there are an infinite number 00:01:48.709 --> 00:01:50.356 of measurable distances between 00:01:50.356 --> 00:01:52.950 any two points, the man will always be 00:01:52.950 --> 00:01:55.454 a minute distance ahead of the biker. 00:01:55.454 --> 00:01:58.220 This, then, will go on indefinitely, 00:01:58.220 --> 00:02:00.721 and the biker will never catch the man. 00:02:02.151 --> 00:02:04.021 But this is absurd! 00:02:04.021 --> 00:02:06.412 For our perceptions tell us the motorcyclist 00:02:06.412 --> 00:02:08.337 would quickly overtake the man. 00:02:08.337 --> 00:02:10.780 Therefore, Zeno's paradox tells us 00:02:10.780 --> 00:02:12.846 that our perceptions are flawed 00:02:12.846 --> 00:02:15.987 and that a change in distance is preposterous. 00:02:16.917 --> 00:02:19.490 ♪ (music) ♪ 00:02:24.823 --> 00:02:27.173 In another of his paradoxes, Zeno talks 00:02:27.173 --> 00:02:29.267 of an arrow being shot at a target. 00:02:29.267 --> 00:02:31.825 If it takes the arrow one second to travel 00:02:31.825 --> 00:02:35.886 60 feet, it would take .5 seconds to travel 00:02:35.886 --> 00:02:37.185 half that distance. 00:02:37.185 --> 00:02:38.634 A quarter second to travel 00:02:38.634 --> 00:02:41.018 half that distance, and so on. 00:02:41.018 --> 00:02:43.447 If this process continues, we'll have 00:02:43.447 --> 00:02:45.893 eventually reach a unit of time during which 00:02:45.893 --> 00:02:48.416 the arrow will occupy a space at complete rest. 00:02:48.666 --> 00:02:51.035 Let's call this unit of duration this time 00:02:51.035 --> 00:02:52.452 "a moment". 00:02:52.452 --> 00:02:54.317 If the arrow's trajectory is the sum 00:02:54.317 --> 00:02:56.164 of these stationary moments, 00:02:56.164 --> 00:02:58.718 then how will the arrow ever reach its target? 00:02:59.193 --> 00:03:02.063 And thus motion is nonsensical. 00:03:02.833 --> 00:03:05.459 Zeno's paradoxes have challenged scholars, 00:03:05.459 --> 00:03:07.805 philosophers, and mathematicians for over 00:03:07.805 --> 00:03:09.101 2,500 years. 00:03:10.221 --> 00:03:12.639 If nothing else, they force us 00:03:12.639 --> 00:03:15.064 to continuously reconsider our reasoning 00:03:15.064 --> 00:03:18.279 about the nature of space and time.