WEBVTT 00:00:07.837 --> 00:00:11.207 We live in a vast universe, on a small wet planet, 00:00:11.207 --> 00:00:12.677 where billions of years ago 00:00:12.677 --> 00:00:16.017 single-celled life forms evolved from the same elements 00:00:16.017 --> 00:00:18.722 as all non-living material around them, 00:00:18.722 --> 00:00:23.312 proliferating and radiating into an incredible ray of complex life forms. 00:00:23.312 --> 00:00:27.242 All of this— living and inanimate, microscopic and cosmic— 00:00:27.242 --> 00:00:31.402 is governed by mathematical laws with apparently arbitrary constants. 00:00:31.402 --> 00:00:33.313 And this opens up a question: 00:00:33.313 --> 00:00:36.263 If the universe is completely governed by these laws, 00:00:36.263 --> 00:00:39.853 couldn’t a powerful enough computer simulate it exactly? 00:00:39.853 --> 00:00:43.853 Could our reality actually be an incredibly detailed simulation 00:00:43.853 --> 00:00:47.243 set in place by a much more advanced civilization? NOTE Paragraph 00:00:47.243 --> 00:00:49.453 This idea may sound like science fiction, 00:00:49.453 --> 00:00:51.933 but it has been the subject of serious inquiry. 00:00:51.933 --> 00:00:55.023 Philosopher Nick Bostrom advanced a compelling argument 00:00:55.023 --> 00:00:57.313 that we’re likely living in a simulation, 00:00:57.313 --> 00:01:00.203 and some scientists also think it’s a possibility. 00:01:00.203 --> 00:01:03.323 These scientists have started thinking about experimental tests 00:01:03.323 --> 00:01:06.463 to find out whether our universe is a simulation. 00:01:06.463 --> 00:01:10.663 They are hypothesizing about what the constraints of the simulation might be, 00:01:10.663 --> 00:01:14.732 and how those constraints could lead to detectable signs in the world. 00:01:14.732 --> 00:01:17.409 So where might we look for those glitches? NOTE Paragraph 00:01:17.409 --> 00:01:20.109 One idea is that as a simulation runs, 00:01:20.109 --> 00:01:22.749 it might accumulate errors over time. 00:01:22.749 --> 00:01:24.169 To correct for these errors 00:01:24.169 --> 00:01:27.739 the simulators could adjust the constants in the laws of nature. 00:01:27.739 --> 00:01:29.419 These shifts could be tiny— 00:01:29.419 --> 00:01:30.259 for instance, 00:01:30.259 --> 00:01:33.889 certain constants we’ve measured with accuracies of parts per million 00:01:33.889 --> 00:01:35.569 have stayed steady for decades, 00:01:35.569 --> 00:01:39.189 so any drift would have to be on an even smaller scale. 00:01:39.189 --> 00:01:42.479 But as we gain more precision in our measurements of these constants, 00:01:42.479 --> 00:01:45.419 we might detect slight changes over time. NOTE Paragraph 00:01:45.419 --> 00:01:49.769 Another possible place to look comes from the concept that finite computing power, 00:01:49.769 --> 00:01:53.119 no matter how huge, can’t simulate infinities. 00:01:53.119 --> 00:01:54.962 If space and time are continuous, 00:01:54.962 --> 00:01:58.402 then even a tiny piece of the universe has infinite points 00:01:58.402 --> 00:02:02.092 and becomes impossible to simulate with finite computing power. 00:02:02.092 --> 00:02:07.212 So a simulation would have to represent space and time in very small pieces. 00:02:07.212 --> 00:02:09.980 These would be almost incomprehensibly tiny. 00:02:09.980 --> 00:02:11.840 But we might be able to search for them 00:02:11.840 --> 00:02:15.160 by using certain subatomic particles as probes. 00:02:15.160 --> 00:02:18.500 The basic principle is this: the smaller something is, 00:02:18.500 --> 00:02:20.910 the more sensitive it will be to disruption— 00:02:20.910 --> 00:02:24.200 think of hitting a pothole on a skateboard versus in a truck. 00:02:24.200 --> 00:02:26.870 Any unit in space-time would be so small 00:02:26.870 --> 00:02:29.810 that most things would travel through it without disruption— 00:02:29.810 --> 00:02:32.870 not just objects large enough to be visible to the naked eye, 00:02:32.870 --> 00:02:36.450 but also molecules, atoms, and even electrons 00:02:36.450 --> 00:02:39.750 and most of the other subatomic particles we’ve discovered. NOTE Paragraph 00:02:39.750 --> 00:02:43.060 If we do discover a tiny unit in space-time 00:02:43.060 --> 00:02:45.690 or a shifting constant in a natural law, 00:02:45.690 --> 00:02:48.360 would that prove the universe is a simulation? 00:02:48.360 --> 00:02:51.280 No— it would only be the first of many steps. 00:02:51.280 --> 00:02:54.210 There could be other explanations for each of those findings. 00:02:54.210 --> 00:02:57.990 And a lot more evidence would be needed to establish the simulation hypothesis 00:02:57.990 --> 00:03:00.140 as a working theory of nature. NOTE Paragraph 00:03:00.140 --> 00:03:01.780 However many tests we design, 00:03:01.780 --> 00:03:04.780 we’re limited by some assumptions they all share. 00:03:04.780 --> 00:03:08.460 Our current understanding of the natural world on the quantum level 00:03:08.460 --> 00:03:11.390 breaks down at what’s known as the planck scale. 00:03:11.390 --> 00:03:14.040 If the unit of space-time is on this scale, 00:03:14.040 --> 00:03:17.760 we wouldn’t be able to look for it with our current scientific understanding. 00:03:17.760 --> 00:03:19.500 There’s still a wide range of things 00:03:19.500 --> 00:03:21.840 that are smaller than what’s currently observable 00:03:21.840 --> 00:03:24.790 but larger than the planck scale to investigate. NOTE Paragraph 00:03:24.790 --> 00:03:29.410 Similarly, shifts in the constants of natural laws could occur so slowly 00:03:29.410 --> 00:03:32.762 that they would only be observable over the lifetime of the universe. 00:03:32.762 --> 00:03:35.142 So they could exist even if we don’t detect them 00:03:35.142 --> 00:03:38.092 over centuries or millennia of measurements. 00:03:38.092 --> 00:03:42.482 We're also biased towards thinking that our universe’s simulator, if it exists, 00:03:42.482 --> 00:03:44.772 makes calculations the same way we do, 00:03:44.772 --> 00:03:47.362 with similar computational limitations. 00:03:47.362 --> 00:03:49.052 Really, we have no way of knowing 00:03:49.052 --> 00:03:52.452 what an alien civilization’s constraints and methods would be— 00:03:52.452 --> 00:03:54.382 but we have to start somewhere. NOTE Paragraph 00:03:54.382 --> 00:03:58.362 It may never be possible to prove conclusively that the universe either is, 00:03:58.362 --> 00:04:00.256 or isn’t, a simulation, 00:04:00.256 --> 00:04:03.066 but we’ll always be pushing science and technology forward 00:04:03.066 --> 00:04:04.746 in pursuit of the question: 00:04:04.746 --> 00:04:07.306 what is the nature of reality?