WEBVTT 00:00:07.814 --> 00:00:12.887 Imagine a distant future when humans reach beyond our pale blue dot, 00:00:12.887 --> 00:00:17.019 forge cities on planets thousands of light-years away, 00:00:17.019 --> 00:00:21.516 and maintain a galactic web of trade and transport. 00:00:21.516 --> 00:00:25.406 What would it take for our civilization to make that leap? 00:00:25.406 --> 00:00:28.356 There are many things to consider— how would we communicate? 00:00:28.356 --> 00:00:30.996 What might a galactic government look like? 00:00:30.996 --> 00:00:33.726 And one of the most fundamental of all: 00:00:33.726 --> 00:00:37.616 where would we get enough energy to power that civilization— 00:00:37.616 --> 00:00:43.582 its industry, its terraforming operations, and its starships? NOTE Paragraph 00:00:43.582 --> 00:00:47.582 An astronomer named Nikolai Kardashev proposed a scale 00:00:47.582 --> 00:00:52.452 to quantify an evolving civilization’s increasing energy needs. 00:00:52.452 --> 00:00:56.452 In the first evolutionary stage, which we’re currently in, 00:00:56.452 --> 00:00:59.832 planet-based fuel sources like fossil fuels, 00:00:59.832 --> 00:01:02.352 solar panels and nuclear power plants 00:01:02.352 --> 00:01:07.136 are probably enough to settle other planets inside our own solar system, 00:01:07.136 --> 00:01:09.956 but not much beyond that. 00:01:09.956 --> 00:01:13.165 For a civilization on the third and final stage, 00:01:13.165 --> 00:01:18.222 expansion on a galactic scale would require about 100 billion times 00:01:18.222 --> 00:01:25.993 more energy than the full 385 yotta joules our sun releases every second. 00:01:25.993 --> 00:01:28.863 Barring a breakthrough in exotic physics, 00:01:28.863 --> 00:01:32.307 there’s only one energy source that could suffice: 00:01:32.307 --> 00:01:35.447 a supermassive black hole. NOTE Paragraph 00:01:35.447 --> 00:01:39.447 It’s counterintuitive to think of black holes as energy sources, 00:01:39.447 --> 00:01:44.033 but that’s exactly what they are, thanks to their accretion disks: 00:01:44.033 --> 00:01:49.905 circular, flat structures formed by matter falling into the event horizon. NOTE Paragraph 00:01:49.905 --> 00:01:52.985 Because of conservation of angular momentum, 00:01:52.985 --> 00:01:56.985 particles there don’t just plummet straight into the black hole. 00:01:56.985 --> 00:02:00.215 Instead, they slowly spiral. 00:02:00.215 --> 00:02:03.565 Due to the intense gravitational field of the black hole, 00:02:03.565 --> 00:02:07.175 these particles convert their potential energy to kinetic energy 00:02:07.175 --> 00:02:10.005 as they inch closer to the event horizon. 00:02:10.005 --> 00:02:12.935 Particle interactions allow for this kinetic energy 00:02:12.935 --> 00:02:15.455 to be radiated out into space 00:02:15.455 --> 00:02:18.934 at an astonishing matter-to-energy efficiency: 00:02:18.934 --> 00:02:25.963 6% for non-rotating black holes, and up to 32% for rotating ones. 00:02:25.963 --> 00:02:29.523 This drastically outshines nuclear fission, 00:02:29.523 --> 00:02:32.803 currently the most efficient widely available mechanism 00:02:32.803 --> 00:02:35.333 to extract energy from mass. 00:02:35.333 --> 00:02:42.432 Fission converts just 0.08% of a Uranium atom into energy. NOTE Paragraph 00:02:42.432 --> 00:02:46.123 The key to harnessing this power may lie in a structure 00:02:46.123 --> 00:02:52.152 devised by physicist Freeman Dyson, known as the Dyson sphere. 00:02:52.152 --> 00:02:56.803 In the 1960s, Dyson proposed that an advanced planetary civilization 00:02:56.803 --> 00:03:01.020 could engineer an artificial sphere around their main star, 00:03:01.020 --> 00:03:06.109 capturing all of its radiated energy to satisfy their needs. 00:03:06.109 --> 00:03:09.319 A similar, though vastly more complicated design 00:03:09.319 --> 00:03:12.799 could theoretically be applied to black holes. 00:03:12.799 --> 00:03:17.334 In order to produce energy, black holes need to be continuously fed— 00:03:17.334 --> 00:03:20.584 so we wouldn’t want to fully cover it with a sphere. 00:03:20.584 --> 00:03:23.724 Even if we did, the plasma jets that shoot from the poles 00:03:23.724 --> 00:03:26.134 of many supermassive black holes 00:03:26.134 --> 00:03:30.134 would blow any structure in their way to smithereens. NOTE Paragraph 00:03:30.134 --> 00:03:33.784 So instead, we might design a sort of Dyson ring, 00:03:33.784 --> 00:03:37.074 made of massive, remotely controlled collectors. 00:03:37.074 --> 00:03:40.024 They’d swarm in an orbit around a black hole, 00:03:40.024 --> 00:03:44.024 perhaps on the plane of its accretion disk, but farther out. 00:03:44.024 --> 00:03:46.714 These devices could use mirror-like panels 00:03:46.714 --> 00:03:50.054 to transmit the collected energy to a powerplant, 00:03:50.054 --> 00:03:52.750 or a battery for storage. 00:03:52.750 --> 00:03:57.704 We’d need to ensure that these collectors are built at just the right radius: 00:03:57.704 --> 00:04:00.734 too close and they’d melt from the radiated energy. 00:04:00.734 --> 00:04:05.537 Too far, and they’d only collect a tiny fraction of the available energy 00:04:05.537 --> 00:04:09.187 and might be disrupted by stars orbiting the black hole. 00:04:09.187 --> 00:04:14.071 We would likely need several Earths worth of highly reflective material 00:04:14.071 --> 00:04:17.181 like hematite to construct the full system— 00:04:17.181 --> 00:04:23.053 plus a few more dismantled planets to make a legion of construction robots. 00:04:23.053 --> 00:04:27.243 Once built, the Dyson ring would be a technological masterpiece, 00:04:27.243 --> 00:04:32.495 powering a civilization spread across every arm of a galaxy. NOTE Paragraph 00:04:32.495 --> 00:04:35.085 This all may seem like wild speculation. 00:04:35.085 --> 00:04:38.255 But even now, in our current energy crisis, 00:04:38.255 --> 00:04:41.795 we’re confronted by the limited resources of our planet. 00:04:41.795 --> 00:04:45.795 New ways of sustainable energy production will always be needed, 00:04:45.795 --> 00:04:48.825 especially as humanity works towards the survival 00:04:48.825 --> 00:04:52.035 and technological progress of our species. 00:04:52.035 --> 00:04:54.855 Perhaps there’s already a civilization out there 00:04:54.855 --> 00:04:58.055 that has conquered these astronomical giants. 00:04:58.055 --> 00:04:59.935 We may even be able to tell 00:04:59.935 --> 00:05:03.925 by seeing the light from their black hole periodically dim 00:05:03.925 --> 00:05:08.175 as pieces of the Dyson ring pass between us and them. 00:05:08.175 --> 00:05:13.081 Or maybe these superstructures are fated to remain in the realm of theory. 00:05:13.081 --> 00:05:17.345 Only time— and our scientific ingenuity— will tell.