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These are the user uploaded subtitles that are being translated: 1 00:00:03,044 --> 00:00:07,180 Space -- a maelstrom of chaos and violence. 2 00:00:07,182 --> 00:00:10,316 Stars gobbling up other stars. 3 00:00:10,318 --> 00:00:13,519 Black holes eating up entire star systems. 4 00:00:13,521 --> 00:00:16,422 Galaxies colliding with other galaxies. 5 00:00:17,223 --> 00:00:20,058 The Universe is a hostile place. 6 00:00:20,060 --> 00:00:23,127 You are blowing up a star. 7 00:00:23,129 --> 00:00:26,664 There's no way to describe that kind of energy. 8 00:00:26,666 --> 00:00:30,167 The hidden mechanism controlling these phenomenon -- 9 00:00:30,169 --> 00:00:31,902 orbits. 10 00:00:31,904 --> 00:00:34,704 If you understand all possible orbits, 11 00:00:34,706 --> 00:00:38,040 you understand the dynamics driving the Universe. 12 00:00:38,042 --> 00:00:42,311 Orbits hold everything together and tear it all apart. 13 00:00:42,313 --> 00:00:44,946 Extreme orbits mean colliding galaxies, 14 00:00:44,948 --> 00:00:48,249 collapsing dust clouds, the very creation of life, 15 00:00:48,251 --> 00:00:49,384 as well as destruction. 16 00:00:50,819 --> 00:00:52,953 Extreme orbits -- 17 00:00:52,955 --> 00:00:55,689 Masters of life and death in our Universe. 18 00:00:55,691 --> 00:00:59,691 ♪ How the Universe Works 2x05 ♪ Extreme Orbits Original Air Date on August 8, 2012 19 00:00:59,692 --> 00:01:03,692 == sync, corrected by elderman == 20 00:01:09,903 --> 00:01:12,437 This is our solar system. 21 00:01:12,439 --> 00:01:16,607 8 planets, more than 150 moons, 22 00:01:16,609 --> 00:01:22,312 billions of space rocks, dust, and gas 23 00:01:22,314 --> 00:01:25,215 all orbit a single star 24 00:01:25,217 --> 00:01:31,487 in a giant whirling disk 10 billion miles across. 25 00:01:31,489 --> 00:01:34,656 It's been this way for 4 billion years. 26 00:01:34,658 --> 00:01:37,859 Everything moves around in an orderly fashion, 27 00:01:37,861 --> 00:01:40,428 serene and stable. 28 00:01:44,066 --> 00:01:46,367 But our solar system is unusual. 29 00:01:48,203 --> 00:01:52,972 Elsewhere in our Universe, orbits are nothing like this. 30 00:01:52,974 --> 00:01:58,544 They're unstable, chaotic, even destructive. 31 00:02:02,115 --> 00:02:03,615 Even in the nearby Universe, 32 00:02:03,617 --> 00:02:07,084 we see incredibly violent examples of orbits -- 33 00:02:07,086 --> 00:02:10,120 giant planets that hurtle in toward their stars. 34 00:02:10,122 --> 00:02:12,189 We see shock waves of thousands of degrees 35 00:02:12,191 --> 00:02:13,857 perpetuate through the atmosphere. 36 00:02:13,859 --> 00:02:15,292 There are planets that dip 37 00:02:15,294 --> 00:02:17,527 right over the surfaces of other stars, 38 00:02:17,529 --> 00:02:20,630 huge stars orbiting each other, multiple orbital systems, 39 00:02:20,632 --> 00:02:22,498 where there's just chaos, 40 00:02:22,500 --> 00:02:24,834 and entire objects can be kicked out of the system. 41 00:02:24,836 --> 00:02:27,236 Stars gobbling up other stars. 42 00:02:27,238 --> 00:02:30,672 Black holes eating up entire star systems. 43 00:02:30,674 --> 00:02:34,008 Galaxies colliding with other galaxies. 44 00:02:34,010 --> 00:02:35,209 That's the norm. 45 00:02:38,342 --> 00:02:42,478 Earth is an oasis of water and warmth. 46 00:02:42,480 --> 00:02:48,550 Life flourishes because of how we orbit the Sun. 47 00:02:48,552 --> 00:02:53,087 Earth's orbit is almost circular. 48 00:02:53,089 --> 00:02:57,090 We stay about the same distance from the Sun all year round. 49 00:03:00,161 --> 00:03:03,262 The temperature here is relatively constant. 50 00:03:03,264 --> 00:03:05,731 And Earth's orbit has been stable 51 00:03:05,733 --> 00:03:09,401 for the past 4 1/2 billion years. 52 00:03:10,970 --> 00:03:14,339 Without this stability, we would not exist. 53 00:03:14,341 --> 00:03:19,009 To create DNA out of the oceans takes hundreds of millions, 54 00:03:19,011 --> 00:03:20,944 perhaps even a billion years. 55 00:03:20,946 --> 00:03:24,247 And for that stability, you need circular orbits. 56 00:03:24,249 --> 00:03:27,217 And so without the stability of the solar system 57 00:03:27,219 --> 00:03:30,186 and the Earth's orbit, there's no life on Earth. 58 00:03:34,925 --> 00:03:37,159 We owe everything to Earth's orbit. 59 00:03:37,161 --> 00:03:39,261 We get a gentle ride. 60 00:03:39,263 --> 00:03:42,664 In an otherwise violent Universe, 61 00:03:42,666 --> 00:03:46,333 we've hit the orbital jackpot. 62 00:03:46,335 --> 00:03:50,337 Yet, chaos is never far away. 63 00:03:50,339 --> 00:03:52,372 Even within our solar system, 64 00:03:52,374 --> 00:03:55,174 there are extreme and violent orbits, 65 00:03:55,176 --> 00:03:58,978 where life could never survive. 66 00:03:58,980 --> 00:04:02,547 Mercury -- the closest rock to the Sun 67 00:04:02,549 --> 00:04:06,551 and the smallest planet in the solar system. 68 00:04:06,553 --> 00:04:10,121 Its orbit stretches into an oval shape. 69 00:04:10,123 --> 00:04:11,522 At its furthest point, 70 00:04:11,524 --> 00:04:15,359 Mercury is 43 million miles from the Sun. 71 00:04:15,361 --> 00:04:20,430 But at its closest point, it's just 28 million. 72 00:04:20,432 --> 00:04:24,000 This close in, it's hot. 73 00:04:24,002 --> 00:04:27,469 800 degrees Fahrenheit, hotter than a baker's oven. 74 00:04:27,471 --> 00:04:30,906 Also, because there's very little atmosphere on Mercury, 75 00:04:30,908 --> 00:04:32,107 you'd choke. 76 00:04:32,109 --> 00:04:34,275 And because there's no air to speak of, 77 00:04:34,277 --> 00:04:36,644 the blood in your body would boil 78 00:04:36,646 --> 00:04:38,579 and it would burst your skin. 79 00:04:38,581 --> 00:04:41,682 You would literally explode on the surface of Mercury. 80 00:04:45,319 --> 00:04:47,454 But the temperature can also fall 81 00:04:47,456 --> 00:04:50,890 to 300 degrees below zero, 82 00:04:50,892 --> 00:04:54,994 three times colder than the coldest place on Earth. 83 00:04:56,429 --> 00:05:00,131 Mercury has the most extreme temperature variations 84 00:05:00,133 --> 00:05:03,001 of any planet in the solar system. 85 00:05:03,003 --> 00:05:07,104 But it's also proof that orbits don't just loop. 86 00:05:07,106 --> 00:05:12,142 With each revolution around the Sun, Mercury's path shifts. 87 00:05:12,144 --> 00:05:16,879 Over thousands of years, the planet follows a daisy pattern. 88 00:05:18,682 --> 00:05:20,649 At the other end of the solar system, 89 00:05:20,651 --> 00:05:24,686 there's Pluto, 4 billion miles from the Sun. 90 00:05:24,688 --> 00:05:30,191 The further away an object is, the slower its orbit. 91 00:05:30,793 --> 00:05:37,130 Pluto takes 248 years to complete a single loop. 92 00:05:37,132 --> 00:05:40,066 And Pluto is an anomaly. 93 00:05:40,068 --> 00:05:42,468 Its stretched orbit 94 00:05:42,470 --> 00:05:46,104 is on a completely different plane from the major planets, 95 00:05:46,106 --> 00:05:50,642 and it creates an amazing spectacle. 96 00:05:50,644 --> 00:05:52,310 During most of its orbit, 97 00:05:52,312 --> 00:05:56,280 Pluto is a frozen block of ice and rock. 98 00:05:56,282 --> 00:06:00,117 But as it gets closer to the Sun, summer begins. 99 00:06:01,652 --> 00:06:07,456 When Pluto warms up, the frozen ices on the surface of Pluto -- 100 00:06:07,458 --> 00:06:10,259 these are water ices, carbon dioxide, 101 00:06:10,261 --> 00:06:15,096 even some carbon monoxide, maybe methane ices -- they evaporate. 102 00:06:15,098 --> 00:06:17,632 And you get a fog, and the fog gets thicker. 103 00:06:17,634 --> 00:06:19,200 And then you get thick clouds, 104 00:06:19,202 --> 00:06:22,136 and, suddenly, you have an actual atmosphere around Pluto 105 00:06:22,138 --> 00:06:25,606 that wasn't there before. 106 00:06:25,608 --> 00:06:27,207 This atmosphere 107 00:06:27,209 --> 00:06:30,110 is thickest when Pluto is closest to the Sun. 108 00:06:30,112 --> 00:06:34,080 But as the planet heads back into deep space, 109 00:06:34,082 --> 00:06:38,150 the temperature plummets to 400 degrees below zero. 110 00:06:40,120 --> 00:06:44,756 It begins to snow flakes of frozen nitrogen and methane. 111 00:06:47,326 --> 00:06:49,093 As winter comes, 112 00:06:49,095 --> 00:06:52,563 these gases slowly begin to freeze out of the atmosphere. 113 00:06:52,565 --> 00:06:54,965 They may rain down in a snow-like way, 114 00:06:54,967 --> 00:06:56,833 but, gradually, they accumulate 115 00:06:56,835 --> 00:06:59,335 sort of a glassy, semitransparent layer, 116 00:06:59,337 --> 00:07:02,137 a frozen atmosphere on the surface of Pluto. 117 00:07:02,139 --> 00:07:07,242 After a bitter winter, Pluto drifts closer to the Sun, 118 00:07:07,244 --> 00:07:11,712 and the 248-year cycle begins again. 119 00:07:11,714 --> 00:07:16,850 Extreme changes like these remind us how lucky we are 120 00:07:16,852 --> 00:07:19,619 that earth's orbit is stable and benign. 121 00:07:23,056 --> 00:07:25,056 But it's a delicate balance. 122 00:07:25,058 --> 00:07:28,293 The smallest change could kill us all. 123 00:07:28,295 --> 00:07:32,029 If Earth's orbit were closer to the Sun, 124 00:07:32,031 --> 00:07:35,699 we would be like our closest neighbor, Venus. 125 00:07:35,701 --> 00:07:37,067 Venus is a pretty good example 126 00:07:37,069 --> 00:07:38,735 of what might happen to the Earth 127 00:07:38,737 --> 00:07:41,303 if our orbit shifted a little bit in from where we are now. 128 00:07:41,305 --> 00:07:43,605 Venus has this hugely thick atmosphere 129 00:07:43,607 --> 00:07:45,173 that traps all of the heat, 130 00:07:45,175 --> 00:07:47,575 and the surface is close to 900 degrees. 131 00:07:47,577 --> 00:07:50,545 If we moved even just a little bit closer to the Sun, 132 00:07:50,547 --> 00:07:52,179 we would become more like Venus. 133 00:07:52,181 --> 00:07:56,550 Oceans would boil away. 134 00:07:56,552 --> 00:07:58,718 Our planet would become a desert. 135 00:07:58,720 --> 00:08:01,520 Life would be destroyed. 136 00:08:03,723 --> 00:08:07,225 A small shift in the opposite direction, 137 00:08:07,227 --> 00:08:11,829 and instead of boiling, we'd freeze. 138 00:08:11,831 --> 00:08:13,964 You would have snowball Earth, 139 00:08:13,966 --> 00:08:16,733 the Earth completely encased in ice. 140 00:08:16,735 --> 00:08:19,035 And that's only by moving the Earth 141 00:08:19,037 --> 00:08:21,571 a fraction of its distance from the Sun. 142 00:08:27,344 --> 00:08:30,445 The polar ice caps would expand. 143 00:08:30,447 --> 00:08:34,481 Oceans would freeze. 144 00:08:34,483 --> 00:08:37,651 A permanent ice age would begin. 145 00:08:37,653 --> 00:08:40,553 The smallest shift in Earth's orbit, 146 00:08:40,555 --> 00:08:43,322 and we'd die by fire or ice. 147 00:08:44,491 --> 00:08:47,292 Orbits allow life to flourish. 148 00:08:50,596 --> 00:08:53,331 But they can also cause chaos. 149 00:08:55,667 --> 00:08:59,569 Orbits are even capable of destroying entire stars. 150 00:09:08,263 --> 00:09:12,771 Our planet's orbit makes life possible. 151 00:09:12,773 --> 00:09:16,213 But most orbits are violent. 152 00:09:20,491 --> 00:09:26,296 Space is a cosmic freeway. Nothing stands still. 153 00:09:26,298 --> 00:09:30,402 Everything moves around everything else, 154 00:09:30,404 --> 00:09:33,404 thanks to a single force -- gravity. 155 00:09:36,108 --> 00:09:39,048 Gravity is the universal force of attraction 156 00:09:39,050 --> 00:09:41,951 that spreads throughout the Universe itself. 157 00:09:41,953 --> 00:09:44,256 It's the force that holds stars together. 158 00:09:44,258 --> 00:09:47,467 It's the force that binds the solar system together. 159 00:09:47,469 --> 00:09:50,946 All objects have gravity, 160 00:09:50,948 --> 00:09:53,761 so all objects attract each other. 161 00:09:53,763 --> 00:09:58,036 The more mass an object has, the stronger its attraction. 162 00:09:58,038 --> 00:10:01,772 That's why falling apples are pulled toward Earth. 163 00:10:04,443 --> 00:10:08,578 In our solar system, the biggest object is the Sun. 164 00:10:11,849 --> 00:10:17,190 It's 700 times more massive than all the planets put together. 165 00:10:17,192 --> 00:10:20,493 The titanic force of the Sun's gravity 166 00:10:20,495 --> 00:10:22,862 pulls all the planets inward. 167 00:10:22,864 --> 00:10:26,698 But something stops them from falling in. 168 00:10:26,700 --> 00:10:30,134 The planets are in constant motion. 169 00:10:30,136 --> 00:10:34,336 They fly through space at incredible speed -- 170 00:10:34,338 --> 00:10:38,273 not directly toward the sun but sideways, 171 00:10:38,275 --> 00:10:40,208 creating a tug-of-war 172 00:10:40,210 --> 00:10:44,479 between the Sun's gravity and the planets' speed. 173 00:10:44,481 --> 00:10:49,257 When the two balance out, the planet loops around the Sun. 174 00:10:49,259 --> 00:10:51,960 We call this an orbit. 175 00:10:51,962 --> 00:10:55,430 An orbit is simply the motion, 176 00:10:55,432 --> 00:10:59,667 the path of an object around another object due to gravity. 177 00:10:59,669 --> 00:11:02,870 So you can have circular orbits. You can have elliptical orbits. 178 00:11:02,872 --> 00:11:05,606 Even if I were to take a ball and throw it in the air 179 00:11:05,608 --> 00:11:07,208 and catch it, very briefly, 180 00:11:07,210 --> 00:11:10,343 that ball is an orbit around the center of the Earth. 181 00:11:10,345 --> 00:11:12,709 It's just motion affected by gravity. 182 00:11:12,711 --> 00:11:16,807 Imagine what would happen 183 00:11:16,809 --> 00:11:19,943 if the Sun had no gravity. 184 00:11:19,945 --> 00:11:23,480 The planets' speed would shoot them out into space. 185 00:11:25,082 --> 00:11:28,785 On the other hand, if the planets stopped moving, 186 00:11:28,787 --> 00:11:31,254 gravity would pull them into the Sun. 187 00:11:37,660 --> 00:11:42,364 All orbits are a balance between gravity and motion. 188 00:11:46,768 --> 00:11:50,537 We like to think the Universe runs like clockwork, 189 00:11:50,539 --> 00:11:52,638 everything neat and orderly, 190 00:11:52,640 --> 00:11:58,009 the planets moving in cosmic harmony. 191 00:11:58,011 --> 00:11:59,243 But that's wrong. 192 00:11:59,245 --> 00:12:03,914 Orbits can be wild and unpredictable. 193 00:12:03,916 --> 00:12:06,883 And the more objects there are, 194 00:12:06,885 --> 00:12:11,188 the more unpredictable their orbits become. 195 00:12:11,190 --> 00:12:14,391 Things can get complicated when you have more than two objects 196 00:12:14,393 --> 00:12:16,059 all trying to orbit around each other. 197 00:12:16,061 --> 00:12:19,929 Then an orbit can actually loop between one object and another. 198 00:12:19,931 --> 00:12:22,197 Speeds can get faster and slower. 199 00:12:22,199 --> 00:12:25,100 An orbit doesn't have to be just one regular path. 200 00:12:28,937 --> 00:12:31,338 The Universe's creativity 201 00:12:31,340 --> 00:12:32,840 defies the imagination. 202 00:12:32,842 --> 00:12:38,644 Travel out beyond Pluto, halfway to the nearest star, 203 00:12:38,646 --> 00:12:44,916 and you find these -- comets, chunks of ice and rock. 204 00:12:44,918 --> 00:12:47,652 They float in vast clouds, 205 00:12:47,654 --> 00:12:53,124 frozen remnants from the dawn of our solar system. 206 00:12:53,126 --> 00:12:57,494 Every so often, one falls towards the Sun. 207 00:12:57,496 --> 00:12:59,729 They can start a trillion miles out 208 00:12:59,731 --> 00:13:02,432 and fall right above the surface of the Sun. 209 00:13:02,434 --> 00:13:05,668 So when they're really far away, they're hardly moving at all. 210 00:13:05,670 --> 00:13:07,636 When they're whipping past the Sun, 211 00:13:07,638 --> 00:13:09,605 they're moving really, really fast. 212 00:13:09,607 --> 00:13:11,907 And so, these can be some of the most extreme orbits 213 00:13:11,909 --> 00:13:13,275 in the solar system. 214 00:13:13,277 --> 00:13:16,611 They can be so elongated, they're almost a straight line. 215 00:13:18,247 --> 00:13:23,350 Comets travel at up to a million miles an hour. 216 00:13:23,352 --> 00:13:29,723 They're cosmic missiles guided by gravity and speed. 217 00:13:29,725 --> 00:13:34,960 Comets show us how destructive orbits can be. 218 00:13:34,962 --> 00:13:37,262 Many plunge into the Sun... 219 00:13:39,799 --> 00:13:43,167 ...or crash into planets. 220 00:13:43,169 --> 00:13:44,802 If a comet were to hit the Earth, 221 00:13:44,804 --> 00:13:48,672 perhaps 5, 6 miles across... 222 00:13:48,674 --> 00:13:52,008 Watch out. It would be a planet-buster. 223 00:13:52,010 --> 00:13:53,509 It would be an object 224 00:13:53,511 --> 00:13:57,479 sufficient to wipe out all life as we know it on the planet. 225 00:13:57,481 --> 00:14:02,150 But most comets miss. 226 00:14:02,152 --> 00:14:04,686 They fly in from deep space 227 00:14:04,688 --> 00:14:08,357 and out again on million-year orbits. 228 00:14:11,862 --> 00:14:14,763 But move beyond our solar system, 229 00:14:14,765 --> 00:14:18,833 and orbits become even more violent. 230 00:14:18,835 --> 00:14:23,203 Death spirals rip apart entire planets... 231 00:14:24,438 --> 00:14:29,475 ...shred stars, and even tear holes in space. 232 00:14:48,034 --> 00:14:51,299 The Universe is unimaginably big, 233 00:14:51,300 --> 00:14:54,365 so there should be other Earth-like worlds out there. 234 00:14:54,367 --> 00:14:54,713 Scientists looking for habitable planets 235 00:14:54,714 --> 00:14:57,548 thought they would find orbits just like ours. 236 00:14:58,232 --> 00:14:59,691 They were wrong. 237 00:14:59,716 --> 00:15:02,548 Now we're on HD 154088. 238 00:15:02,549 --> 00:15:04,615 They were wrong. 239 00:15:04,617 --> 00:15:08,485 Now we're on HD 154088. 240 00:15:08,487 --> 00:15:11,954 And there it is. Looks good. 241 00:15:11,956 --> 00:15:14,590 We have discovered hundreds of planets 242 00:15:14,592 --> 00:15:18,527 outside our solar system, but they're not like Earth at all. 243 00:15:18,529 --> 00:15:25,265 These are strange, alien worlds with unfamiliar orbits. 244 00:15:25,267 --> 00:15:28,401 What we're finding among extra-solar planets 245 00:15:28,403 --> 00:15:33,672 is an incredible diversity of these orbital shapes and sizes. 246 00:15:33,674 --> 00:15:37,643 Some of the orbits are extremely tight around their host star, 247 00:15:37,645 --> 00:15:40,746 the planet going around in just hours or days. 248 00:15:40,748 --> 00:15:44,716 So we're seeing interactions and shapes and sizes of orbits 249 00:15:44,718 --> 00:15:46,618 that are like nothing we ever imagined. 250 00:15:50,757 --> 00:15:53,092 Some worlds are so hostile, 251 00:15:53,094 --> 00:15:56,395 life as we know it would be impossible. 252 00:15:56,397 --> 00:16:00,899 This is WASP-18b. 253 00:16:00,901 --> 00:16:02,601 It's a hot Jupiter, 254 00:16:02,603 --> 00:16:07,238 a class of huge planets that closely orbit their stars. 255 00:16:10,308 --> 00:16:16,913 WASP-18b is 50 times closer to its star than we are to the Sun. 256 00:16:16,915 --> 00:16:21,384 It's so close, it orbits in less than one day. 257 00:16:23,753 --> 00:16:27,389 If you had said, "What's the weirdest, least-likely orbit 258 00:16:27,391 --> 00:16:29,157 you could possibly imagine?" 259 00:16:29,159 --> 00:16:31,660 I would have said, "take something like Jupiter 260 00:16:31,662 --> 00:16:35,129 and plop it down right next to a star, 5 million miles away." 261 00:16:35,131 --> 00:16:37,732 And it turns out, I would be totally wrong. 262 00:16:37,734 --> 00:16:39,806 That is an extremely common thing 263 00:16:39,808 --> 00:16:41,475 that we see in the Universe. 264 00:16:41,477 --> 00:16:43,110 In fact, most of the planets 265 00:16:43,112 --> 00:16:44,811 that we're discovering around other stars 266 00:16:44,813 --> 00:16:46,246 appear to be in orbits like that. 267 00:16:46,248 --> 00:16:49,114 This cosmic duel 268 00:16:49,116 --> 00:16:53,318 produces incredibly powerful physical effects. 269 00:16:53,320 --> 00:16:58,156 WASP-18b burns at 4,000 degrees. 270 00:16:58,158 --> 00:17:02,059 Thermal hurricanes blast across its surface. 271 00:17:02,061 --> 00:17:04,227 And both star and planet 272 00:17:04,229 --> 00:17:08,030 are distorted by vast gravitational forces, 273 00:17:08,032 --> 00:17:12,500 the same forces that cause the tides on Earth. 274 00:17:12,502 --> 00:17:15,103 Everybody is familiar with the idea of tides. 275 00:17:15,105 --> 00:17:16,404 In the course of a day, 276 00:17:16,406 --> 00:17:18,439 the level of the oceans get higher and then lower. 277 00:17:18,441 --> 00:17:21,075 Well, that's from the influence of the Sun and the Moon, 278 00:17:21,077 --> 00:17:23,944 from the influence of orbits, things that are going around us 279 00:17:23,946 --> 00:17:25,245 or that we're going around. 280 00:17:25,247 --> 00:17:27,647 If you bring things closer together, 281 00:17:27,649 --> 00:17:29,282 tides become more extreme. 282 00:17:29,284 --> 00:17:31,984 Planets can actually get pulled into different shapes. 283 00:17:35,188 --> 00:17:39,124 WASP-18b was formed in a cold region of space 284 00:17:39,126 --> 00:17:41,726 far away from its star. 285 00:17:41,728 --> 00:17:44,095 Over millions of years, 286 00:17:44,097 --> 00:17:48,031 it spiraled into its present position. 287 00:17:48,033 --> 00:17:50,834 It's locked in a gravitational battle 288 00:17:50,836 --> 00:17:53,035 that can only end one way. 289 00:17:56,539 --> 00:17:59,140 Less than a million years from now, 290 00:17:59,142 --> 00:18:01,075 it will be consumed by fire. 291 00:18:08,949 --> 00:18:12,051 The key conclusion you have to draw is -- 292 00:18:12,053 --> 00:18:16,487 when you see the Universe today, it won't be that way tomorrow 293 00:18:16,489 --> 00:18:19,190 and it won't be that way the week or the millennium 294 00:18:19,192 --> 00:18:22,159 or a billion years later because of gravity. 295 00:18:24,495 --> 00:18:27,797 Our search for Earth-like planets 296 00:18:27,799 --> 00:18:30,099 reveals a destructive Universe, 297 00:18:30,101 --> 00:18:33,236 from the deadly missile-like orbits of comets 298 00:18:33,238 --> 00:18:35,838 to the searing paths of hot Jupiters. 299 00:18:35,840 --> 00:18:39,174 There are even planets 300 00:18:39,176 --> 00:18:42,210 that don't seem to orbit anything at all. 301 00:18:42,212 --> 00:18:45,879 Scientists have recently detected tiny fluctuations 302 00:18:45,881 --> 00:18:48,581 in the light from distant stars. 303 00:18:48,583 --> 00:18:50,482 The only explanation? 304 00:18:50,484 --> 00:18:54,686 A massive object between us and them. 305 00:18:54,688 --> 00:18:59,123 These rogue planets don't orbit a parent star. 306 00:18:59,125 --> 00:19:04,428 They are planetary orphans, all alone in space. 307 00:19:04,430 --> 00:19:08,098 Planets, by definition, go around stars, 308 00:19:08,100 --> 00:19:11,768 so, boy, were we shocked to find rogue planets. 309 00:19:11,770 --> 00:19:15,204 Rogue planets are a contradiction in terms -- 310 00:19:15,206 --> 00:19:17,439 planets without a mother star. 311 00:19:17,441 --> 00:19:19,707 Scientists think 312 00:19:19,709 --> 00:19:23,277 every rogue planet did once orbit a star 313 00:19:23,279 --> 00:19:25,913 until gravity hurled them away. 314 00:19:28,116 --> 00:19:31,651 New solar systems are chaotic places. 315 00:19:31,653 --> 00:19:36,354 Planets tug on each other and dramatically change course. 316 00:19:36,356 --> 00:19:43,927 Some planets even spiral out to wander the galaxy alone. 317 00:19:43,929 --> 00:19:45,696 The presence of rogue planets 318 00:19:45,698 --> 00:19:49,098 shows us that gravity is not just this attractive force 319 00:19:49,100 --> 00:19:51,734 which binds the solar system together. 320 00:19:51,736 --> 00:19:55,069 It can also fling entire planets into outer space. 321 00:19:55,071 --> 00:19:58,739 A recent sky survey suggests 322 00:19:58,741 --> 00:20:03,309 our galaxy contains more rogue planets than stars. 323 00:20:03,311 --> 00:20:07,914 We've discovered orbits we didn't even know were possible. 324 00:20:10,517 --> 00:20:14,452 Gravity and motion keep our Universe in constant turmoil. 325 00:20:16,488 --> 00:20:20,824 Vast orbiting suns cannibalize each other. 326 00:20:20,826 --> 00:20:24,628 Violent vortexes distort space itself. 327 00:20:24,630 --> 00:20:30,298 And powerful forces flick a star like a spinning top. 328 00:20:36,987 --> 00:20:41,090 Gravity causes chaos on an epic scale... 329 00:20:43,727 --> 00:20:46,762 ...hurling planets to their destruction 330 00:20:46,764 --> 00:20:48,964 or firing them off into space. 331 00:20:50,333 --> 00:20:55,570 But the cosmic roller coaster gets even more extreme. 332 00:20:55,572 --> 00:21:01,975 Orbits become so violent, they rip chunks out of stars. 333 00:21:06,713 --> 00:21:08,981 This is HM Cancri, 334 00:21:08,983 --> 00:21:13,985 a binary star system 16,000 light-years from Earth. 335 00:21:13,987 --> 00:21:18,756 They're white dwarfs -- small but incredibly dense. 336 00:21:18,758 --> 00:21:23,593 One teaspoon of white-dwarf matter can weigh 5 tons. 337 00:21:23,595 --> 00:21:27,096 The stars are just 50,000 miles apart, 338 00:21:27,098 --> 00:21:30,866 five times closer than we are to the Moon. 339 00:21:30,868 --> 00:21:36,804 They orbit at more than a million miles an hour. 340 00:21:36,806 --> 00:21:41,175 We have two white dwarves an infinitesimal distance apart, 341 00:21:41,177 --> 00:21:44,612 rotating around each other in 5 1/2 minutes. 342 00:21:44,614 --> 00:21:49,121 This is a world's record for an astronomical body in space. 343 00:21:51,791 --> 00:21:54,959 The forces are immense. 344 00:21:54,961 --> 00:21:58,929 Gravity rips superheated gas out of one star 345 00:21:58,931 --> 00:22:02,566 and slams it into the other. 346 00:22:02,568 --> 00:22:06,235 Scientists believe this orbit is so violent, 347 00:22:06,237 --> 00:22:09,338 it warps the fabric of space itself. 348 00:22:09,340 --> 00:22:15,143 In the process, the stars lose energy, falling even closer. 349 00:22:17,379 --> 00:22:19,848 Eventually, they'll collide... 350 00:22:21,651 --> 00:22:23,985 ...creating a supernova. 351 00:22:30,991 --> 00:22:35,127 A supernova is one of the most violent, 352 00:22:35,129 --> 00:22:38,430 energetic events in the Universe today. 353 00:22:38,432 --> 00:22:41,966 You are blowing up a star. 354 00:22:41,968 --> 00:22:44,534 There's no way to describe that kind of energy. 355 00:22:48,638 --> 00:22:51,339 Some supernovae are so powerful, 356 00:22:51,341 --> 00:22:54,375 they are second only to the Big Bang itself 357 00:22:54,377 --> 00:22:56,944 for energy and sheer power. 358 00:22:56,946 --> 00:22:59,279 They are so magnificent, 359 00:22:59,281 --> 00:23:04,584 they can outshine an entire galaxy of 200 billion stars. 360 00:23:07,020 --> 00:23:09,087 Supernovas can create 361 00:23:09,089 --> 00:23:13,591 one of the weirdest objects in the Universe... 362 00:23:13,593 --> 00:23:15,426 a pulsar. 363 00:23:15,428 --> 00:23:18,528 Pulsars are intensely magnetic stars. 364 00:23:18,530 --> 00:23:22,332 They fire out beams of electromagnetic radiation 365 00:23:22,334 --> 00:23:24,634 that sweep across space. 366 00:23:24,636 --> 00:23:26,537 There are few things in the Universe 367 00:23:26,539 --> 00:23:27,905 more dramatic than a pulsar. 368 00:23:27,907 --> 00:23:30,407 Imagine a ball about 10 miles across 369 00:23:30,409 --> 00:23:32,876 rotating hundreds of times a second 370 00:23:32,878 --> 00:23:35,477 with a density that's almost unimaginable. 371 00:23:35,479 --> 00:23:37,576 1 cubic centimeter of this material 372 00:23:37,578 --> 00:23:40,810 would have as much mass as Mount Everest. 373 00:23:40,812 --> 00:23:45,247 You would feel a gravity that is millions, millions of times 374 00:23:45,249 --> 00:23:47,983 what you're feeling sitting on the surface of the Earth. 375 00:23:47,985 --> 00:23:50,152 You wouldn't just be crushed flat by this. 376 00:23:50,154 --> 00:23:52,587 You would be crushed into a paste 377 00:23:52,589 --> 00:23:54,689 that is only a few atoms thick. 378 00:23:54,691 --> 00:23:59,727 Anything that orbits a pulsar too closely 379 00:23:59,729 --> 00:24:02,396 risks being torn to shreds. 380 00:24:04,899 --> 00:24:08,267 This is the black widow pulsar. 381 00:24:08,269 --> 00:24:12,904 It rips through our galaxy at 600,000 miles an hour. 382 00:24:15,841 --> 00:24:18,443 The shock wave is so vast, 383 00:24:18,445 --> 00:24:22,880 our telescopes can't detect it 5,000 light-years away. 384 00:24:22,882 --> 00:24:25,182 Traveling alongside it, 385 00:24:25,184 --> 00:24:30,520 a brown dwarf bigger than a planet, smaller than a star. 386 00:24:30,522 --> 00:24:34,757 The pair are locked in an orbital dance of death. 387 00:24:34,759 --> 00:24:38,359 The black widow, in some sense, is like a vampire, 388 00:24:38,361 --> 00:24:41,929 sucking the lifeblood from this brown dwarf star, 389 00:24:41,931 --> 00:24:44,931 eating away at its hydrogen and helium fuel. 390 00:24:48,068 --> 00:24:52,370 Radiation blasts the brown dwarf's gases into space. 391 00:24:54,339 --> 00:24:56,606 A pulsar just 10 miles wide 392 00:24:56,608 --> 00:25:00,343 is destroying an object bigger than Jupiter. 393 00:25:00,345 --> 00:25:05,248 Eventually, the brown dwarf will evaporate. 394 00:25:07,117 --> 00:25:12,054 A single pulsar has immense destructive power. 395 00:25:14,891 --> 00:25:16,925 But two pulsars together 396 00:25:16,927 --> 00:25:20,194 can change the shape of the Universe. 397 00:25:20,196 --> 00:25:23,863 This is the only known double-pulsar system 398 00:25:23,865 --> 00:25:26,498 in our galaxy. 399 00:25:26,500 --> 00:25:30,402 Orbiting at 700,000 miles an hour, 400 00:25:30,404 --> 00:25:35,573 their speed and mass make them spin chaotically. 401 00:25:38,843 --> 00:25:41,044 It's incredible to think 402 00:25:41,046 --> 00:25:44,013 of the enormous forces, gravitationally, 403 00:25:44,015 --> 00:25:46,382 that these two stars exert on each other, 404 00:25:46,384 --> 00:25:49,585 causing the whole geometry, the architecture of the system 405 00:25:49,587 --> 00:25:53,555 to change and spin around like a top on the table. 406 00:25:57,559 --> 00:25:59,527 The gravity of the heavier pulsar 407 00:25:59,529 --> 00:26:03,363 makes the smaller one wobble erratically. 408 00:26:03,365 --> 00:26:05,899 It whips around so violently 409 00:26:05,901 --> 00:26:10,970 that the whole star almost tips over, just like a spinning top. 410 00:26:12,372 --> 00:26:15,339 It can't last forever. 411 00:26:15,341 --> 00:26:19,610 85 million years from now, the two pulsars will merge 412 00:26:19,612 --> 00:26:22,779 to form a vast gravitational abyss... 413 00:26:27,550 --> 00:26:32,587 ...the Universe's ultimate monster -- a black hole. 414 00:26:50,922 --> 00:26:53,789 A black hole -- 415 00:26:53,791 --> 00:26:57,793 the most extreme object in the Universe. 416 00:26:57,795 --> 00:27:03,097 At its center, the laws of physics break down. 417 00:27:05,232 --> 00:27:08,568 Time comes to an end. 418 00:27:08,570 --> 00:27:12,072 Gravity is infinite. 419 00:27:12,074 --> 00:27:14,941 A black hole is a bottomless pit of gravity 420 00:27:14,943 --> 00:27:16,476 caused by the death of a star. 421 00:27:16,478 --> 00:27:19,011 There is nothing in the Universe more mysterious 422 00:27:19,013 --> 00:27:20,379 than how black holes work. 423 00:27:20,381 --> 00:27:21,546 If you want to talk about 424 00:27:21,548 --> 00:27:23,281 extreme orbits and extreme gravity, 425 00:27:23,283 --> 00:27:24,549 you're talking black holes. 426 00:27:24,551 --> 00:27:26,252 That is at the top of the list. 427 00:27:26,254 --> 00:27:29,455 Nothing has stronger gravity than a black hole. 428 00:27:29,457 --> 00:27:32,957 It is the mass of something like the Sun or more 429 00:27:32,959 --> 00:27:34,892 compressed down into a ball 430 00:27:34,894 --> 00:27:37,694 that's only a couple of miles across. 431 00:27:37,696 --> 00:27:39,462 50 years ago, 432 00:27:39,464 --> 00:27:42,932 black holes were dismissed as science fiction, 433 00:27:42,934 --> 00:27:45,334 but not anymore. 434 00:27:48,171 --> 00:27:51,873 Now we see them at the center of galaxies, 435 00:27:51,875 --> 00:27:53,841 wandering through outer space. 436 00:27:53,843 --> 00:27:55,509 Black holes, we now know, 437 00:27:55,511 --> 00:27:58,512 are central to the evolution of the Universe. 438 00:28:02,149 --> 00:28:05,684 We now think there may be 100 million black holes 439 00:28:05,686 --> 00:28:08,120 in our galaxy alone. 440 00:28:08,122 --> 00:28:13,423 An encounter with any of them leads to oblivion. 441 00:28:17,461 --> 00:28:21,531 This is one of the largest and hottest stars in the Universe. 442 00:28:21,533 --> 00:28:27,836 It's 20 times more massive than our Sun and 10 times hotter. 443 00:28:34,476 --> 00:28:37,611 Stars like this never live long, 444 00:28:37,613 --> 00:28:42,281 but this one is locked in a diabolic waltz, 445 00:28:42,283 --> 00:28:45,417 trapped in the grip of a black hole. 446 00:28:45,419 --> 00:28:48,352 The gravity here is so powerful, 447 00:28:48,354 --> 00:28:52,223 the star orbits at half a million miles an hour. 448 00:28:56,160 --> 00:28:59,996 The black hole sucks the star's outer layers 449 00:28:59,998 --> 00:29:02,298 into a vast, swirling disk, 450 00:29:02,300 --> 00:29:06,434 a disk so hot it blasts out X-rays 451 00:29:06,436 --> 00:29:11,472 a million times more powerful than our Sun. 452 00:29:17,778 --> 00:29:19,211 This configuration -- 453 00:29:19,213 --> 00:29:21,246 a star orbiting around a black hole -- 454 00:29:21,248 --> 00:29:23,282 is extreme and it's unstable. 455 00:29:23,284 --> 00:29:25,283 First of all, the black hole 456 00:29:25,285 --> 00:29:29,120 is eating away at the atmosphere of its companion star, 457 00:29:29,122 --> 00:29:31,756 but the star itself is unstable. 458 00:29:31,758 --> 00:29:34,926 It will one day undergo a supernova 459 00:29:34,928 --> 00:29:37,595 and perhaps leave a black hole in its wake. 460 00:29:37,597 --> 00:29:39,963 And then it will have two black holes 461 00:29:39,965 --> 00:29:42,098 rotating around each other, 462 00:29:42,100 --> 00:29:45,467 one of the rarest sights in the Universe. 463 00:29:45,469 --> 00:29:49,904 Eventually, these black holes will merge 464 00:29:49,906 --> 00:29:53,140 to create a new, larger monster, 465 00:29:53,142 --> 00:29:57,944 and the cycle of destruction will continue. 466 00:29:57,946 --> 00:30:00,780 But this black hole is small. 467 00:30:00,782 --> 00:30:06,118 Other black holes take violence to a whole new level. 468 00:30:06,120 --> 00:30:09,120 In 2011, astronomers witnessed 469 00:30:09,122 --> 00:30:13,690 one of the biggest explosions ever recorded, 470 00:30:13,692 --> 00:30:18,528 a flash of radiation brighter than 100 billion suns -- 471 00:30:18,530 --> 00:30:22,031 a gamma-ray burst. 472 00:30:22,033 --> 00:30:24,400 It was a spectacular event. 473 00:30:29,539 --> 00:30:33,575 The burst came from a supermassive black hole 474 00:30:33,577 --> 00:30:36,177 at the center of a distant galaxy. 475 00:30:38,980 --> 00:30:40,516 It had been dormant, 476 00:30:40,518 --> 00:30:43,619 but something had shocked it back to life. 477 00:30:46,823 --> 00:30:49,457 If you pass by the event horizon, 478 00:30:49,459 --> 00:30:52,560 an imaginary sphere surrounding the black hole, 479 00:30:52,562 --> 00:30:54,561 that's the point of no return. 480 00:30:54,563 --> 00:30:57,230 It's like the ultimate roach motel -- 481 00:30:57,232 --> 00:30:59,999 everything checks in, nothing checks out. 482 00:31:07,975 --> 00:31:11,944 Several stars were orbiting the black hole 483 00:31:11,946 --> 00:31:13,512 at a safe distance. 484 00:31:13,514 --> 00:31:15,881 Then one of them got too close. 485 00:31:15,883 --> 00:31:19,517 The sleeping giant suddenly awoke. 486 00:31:19,519 --> 00:31:22,220 Immense gravitational forces 487 00:31:22,222 --> 00:31:26,290 stretched the star to its breaking point 488 00:31:26,292 --> 00:31:29,827 until, finally, it was torn apart. 489 00:31:29,829 --> 00:31:32,796 Debris swirled around the black hole, 490 00:31:32,798 --> 00:31:35,866 heated to millions of degrees. 491 00:31:35,868 --> 00:31:40,169 Two giant jets of gamma rays 492 00:31:40,171 --> 00:31:43,105 blasted into space at the speed of light. 493 00:31:46,676 --> 00:31:49,143 A black hole has torn a star apart, 494 00:31:49,145 --> 00:31:52,246 swallowed up half of the material of the star, 495 00:31:52,248 --> 00:31:54,414 and ejected the other half in an event 496 00:31:54,416 --> 00:31:57,350 that is among the most violent things we have ever seen 497 00:31:57,352 --> 00:31:58,918 in the history of astronomy. 498 00:31:58,920 --> 00:32:02,021 The event was so violent, 499 00:32:02,023 --> 00:32:05,724 we saw it from Earth, 3 billion light-years away. 500 00:32:09,662 --> 00:32:15,467 Black holes can suck in planets and rip apart stars. 501 00:32:15,469 --> 00:32:18,668 But gravity doesn't always pull things in. 502 00:32:20,003 --> 00:32:22,737 Any high-school student knows that gravity sucks. 503 00:32:22,739 --> 00:32:24,205 It pulls. It never pushes. 504 00:32:24,207 --> 00:32:26,273 But it's actually more complicated. 505 00:32:26,275 --> 00:32:28,442 That's true when you just have two objects. 506 00:32:28,444 --> 00:32:30,744 But the minute you have more than two objects, 507 00:32:30,746 --> 00:32:32,679 strange things can happen, 508 00:32:32,681 --> 00:32:35,715 and gravity can actually push you away. 509 00:32:35,717 --> 00:32:37,384 You can get very close to a body, 510 00:32:37,386 --> 00:32:39,420 but if you come in at just the right angle 511 00:32:39,422 --> 00:32:42,656 and just the right speed, instead of colliding together, 512 00:32:42,658 --> 00:32:45,092 one object can slingshot the other one away. 513 00:32:45,094 --> 00:32:49,263 Recently, scientists discovered stars 514 00:32:49,265 --> 00:32:53,634 hurtling away from our galaxy at incredible speed. 515 00:32:53,636 --> 00:32:56,636 Normal stars don't do this. 516 00:32:56,638 --> 00:33:02,641 So what could accelerate a star to hypervelocity? 517 00:33:02,643 --> 00:33:05,610 The answer was a surprise. 518 00:33:05,612 --> 00:33:09,313 You can only eject stars at these very, very high velocity, 519 00:33:09,315 --> 00:33:12,416 so close to 700, 800, 1,000 kilometers a second. 520 00:33:12,418 --> 00:33:13,884 You could only eject these 521 00:33:13,886 --> 00:33:16,620 with interactions with a supermassive black hole. 522 00:33:16,622 --> 00:33:20,490 Each hypervelocity star was originally 523 00:33:20,492 --> 00:33:25,828 one of a pair of stars orbiting a supermassive black hole. 524 00:33:25,830 --> 00:33:29,898 When they got too close, gravity pulled them apart. 525 00:33:29,900 --> 00:33:31,933 The black hole catapulted 526 00:33:31,935 --> 00:33:36,604 one star out of the galaxy at 2 million miles an hour. 527 00:33:36,606 --> 00:33:41,709 Eventually, the other was sucked in and destroyed. 528 00:33:41,711 --> 00:33:43,143 The interesting thing here is 529 00:33:43,145 --> 00:33:45,813 that you can get a complete redistribution of stars, 530 00:33:45,815 --> 00:33:48,615 so you have stars that are in the center of the galaxy, 531 00:33:48,617 --> 00:33:51,618 and, suddenly, they're ejected out into intergalactic space. 532 00:33:51,620 --> 00:33:54,988 And it's out here, in deep space, 533 00:33:54,990 --> 00:33:58,091 that orbits are at their most powerful, 534 00:33:58,093 --> 00:34:00,927 smashing entire galaxies together 535 00:34:00,929 --> 00:34:04,696 to create the structure of the Universe itself. 536 00:34:17,937 --> 00:34:20,172 Across the Universe, 537 00:34:20,174 --> 00:34:24,609 extreme gravity is a force of destruction. 538 00:34:24,611 --> 00:34:26,644 The orbits of planets and stars 539 00:34:26,646 --> 00:34:29,614 can be chaotic, unpredictable, and violent. 540 00:34:29,616 --> 00:34:33,551 But on a truly cosmic scale, 541 00:34:33,553 --> 00:34:36,621 gravity is no longer just a destroyer. 542 00:34:40,492 --> 00:34:43,160 It also creates new worlds. 543 00:34:43,162 --> 00:34:47,330 These are galaxies -- giant spinning clusters 544 00:34:47,332 --> 00:34:52,968 of stars, gas, and dust 100,000 light-years across. 545 00:34:54,471 --> 00:34:56,605 Galaxies orbit each other 546 00:34:56,607 --> 00:34:59,841 in the same way planets orbit stars. 547 00:34:59,843 --> 00:35:02,376 Gravity pulls them together. 548 00:35:02,378 --> 00:35:04,978 Their speed keeps them apart. 549 00:35:04,980 --> 00:35:08,715 But, ultimately, gravity always wins. 550 00:35:08,717 --> 00:35:10,951 Entire galaxies smash together. 551 00:35:10,953 --> 00:35:15,521 One of the most spectacular events in the Universe 552 00:35:15,523 --> 00:35:17,256 is when galaxies collide. 553 00:35:17,258 --> 00:35:20,658 You're talking about hundreds of billions of stars 554 00:35:20,660 --> 00:35:22,426 100,000 light-years across, 555 00:35:22,428 --> 00:35:25,328 two of these things slamming into each other. 556 00:35:29,267 --> 00:35:31,334 Collisions between orbiting galaxies 557 00:35:31,336 --> 00:35:35,671 take place over millions of years. 558 00:35:35,673 --> 00:35:39,342 Gravity slowly pulls them together. 559 00:35:44,480 --> 00:35:45,847 And you get these two galaxies 560 00:35:45,849 --> 00:35:48,950 that merge like two fluids mixing together. 561 00:35:48,952 --> 00:35:53,119 And you get long tidal tails as they pass through each other, 562 00:35:53,121 --> 00:35:55,254 but then gravity brings them back together again. 563 00:35:55,256 --> 00:35:57,923 And in the end, you get a full-fledged, 564 00:35:57,925 --> 00:36:01,260 more mature, larger galaxy than you had originally. 565 00:36:07,432 --> 00:36:09,366 On this intergalactic scale, 566 00:36:09,368 --> 00:36:14,137 gravity and motion are no longer destructive forces. 567 00:36:14,139 --> 00:36:18,173 Now they trigger the creation of life itself. 568 00:36:18,175 --> 00:36:21,409 You would think a galactic collision 569 00:36:21,411 --> 00:36:23,211 would be incredibly destructive, 570 00:36:23,213 --> 00:36:24,612 and in one sense, it is, 571 00:36:24,614 --> 00:36:27,415 but in another sense, it's a very creative force. 572 00:36:30,592 --> 00:36:35,264 Colliding galaxies smash vast gas clouds together. 573 00:36:35,266 --> 00:36:39,768 Huge shock waves rip through them, squeezing the gas. 574 00:36:42,271 --> 00:36:45,740 Then something amazing happens -- 575 00:36:45,742 --> 00:36:48,542 the birth of countless stars. 576 00:36:50,511 --> 00:36:53,313 It's incredible to think about two galaxies 577 00:36:53,315 --> 00:36:56,381 that gravitationally attract each other and collide. 578 00:36:56,383 --> 00:36:58,182 What could be more destructive? 579 00:36:58,184 --> 00:37:02,719 But, in fact, there is a power of construction in such mergers, 580 00:37:02,721 --> 00:37:05,655 because as two galaxies come together, 581 00:37:05,657 --> 00:37:08,357 the gases are compressed, and sometimes, 582 00:37:08,359 --> 00:37:12,361 the gases are compressed so much that you get the birth of stars 583 00:37:12,363 --> 00:37:16,098 and the associated planets around those stars. 584 00:37:16,100 --> 00:37:19,701 And so, in the titanic collision between two galaxies, 585 00:37:19,703 --> 00:37:22,604 you can get the birth of stars and planets 586 00:37:22,606 --> 00:37:25,606 and perhaps eventually life on those planets. 587 00:37:30,377 --> 00:37:32,445 Sometimes, these collisions 588 00:37:32,447 --> 00:37:34,780 trigger a chain reaction... 589 00:37:39,654 --> 00:37:42,689 ...two spiral galaxies in mid-collision 590 00:37:42,691 --> 00:37:46,192 creating stars and planets. 591 00:37:49,329 --> 00:37:51,796 But this time, there's a difference. 592 00:37:58,503 --> 00:38:00,436 Some of these new stars 593 00:38:00,438 --> 00:38:03,773 are massive, unstable, and short-lived. 594 00:38:03,775 --> 00:38:05,541 They explode. 595 00:38:05,543 --> 00:38:10,513 Each explosion blasts out new shock waves 596 00:38:10,515 --> 00:38:14,449 and triggers the birth of even more stars. 597 00:38:14,451 --> 00:38:17,619 Astronomers call this a starburst. 598 00:38:20,556 --> 00:38:24,725 It's the ultimate example of gravity's creative power. 599 00:38:26,394 --> 00:38:28,895 A starburst galaxy is one 600 00:38:28,897 --> 00:38:31,798 that is creating stars at a much higher rate 601 00:38:31,800 --> 00:38:34,400 than we usually see in normal galaxies. 602 00:38:34,402 --> 00:38:35,735 And so, it's amazing 603 00:38:35,737 --> 00:38:38,370 that you can have such a beautiful, creative process 604 00:38:38,372 --> 00:38:41,139 coming out of something so violent and destructive. 605 00:38:43,976 --> 00:38:46,277 Gravity and motion, 606 00:38:46,279 --> 00:38:50,079 the two forces that give birth to every new star, 607 00:38:50,081 --> 00:38:54,249 also weave together the fabric of the Universe itself. 608 00:38:57,420 --> 00:39:02,089 Our cosmos is not random. It has structure. 609 00:39:02,091 --> 00:39:07,860 The Universe is a vast three-dimensional tapestry. 610 00:39:07,862 --> 00:39:11,397 Each of these threads and filaments 611 00:39:11,399 --> 00:39:14,267 contains billions of galaxies. 612 00:39:14,269 --> 00:39:17,603 It's the scaffolding that holds everything together, 613 00:39:17,605 --> 00:39:21,607 the cosmic web. 614 00:39:21,609 --> 00:39:23,876 And we think about scaffolding of a building, 615 00:39:23,878 --> 00:39:25,544 it's just sitting there, static. 616 00:39:25,546 --> 00:39:27,111 But, in fact, this scaffolding 617 00:39:27,113 --> 00:39:29,046 is quite dynamic and quite amazing 618 00:39:29,048 --> 00:39:30,681 because all of the constituents 619 00:39:30,683 --> 00:39:33,149 are moving around at very high speeds, 620 00:39:33,151 --> 00:39:34,917 crashing into one another -- 621 00:39:34,919 --> 00:39:37,652 galaxies, stars, black holes, supernovae -- 622 00:39:37,654 --> 00:39:40,555 all in this tremendous cosmic dance. 623 00:39:40,557 --> 00:39:46,160 The cosmic web is incomprehensibly vast. 624 00:39:46,162 --> 00:39:48,929 Each thread is full of motion. 625 00:39:48,931 --> 00:39:52,332 Galaxies form, orbit, and collide, 626 00:39:52,334 --> 00:39:56,936 countless billions in a constant stream. 627 00:39:56,938 --> 00:39:59,203 Every filament is a galactic freeway 628 00:39:59,205 --> 00:40:05,667 with an endless flow of traffic, each point of light a galaxy. 629 00:40:07,665 --> 00:40:14,161 It's rush hour 24/7, and sometimes, there's gridlock. 630 00:40:14,163 --> 00:40:16,497 Every billion light-years, 631 00:40:16,499 --> 00:40:20,034 several filaments join to form a knot. 632 00:40:22,170 --> 00:40:25,472 Whole clusters collide to form 633 00:40:25,474 --> 00:40:30,075 some of the largest structures we know of -- superclusters. 634 00:40:30,077 --> 00:40:36,615 This is one of them -- Abell 2744. 635 00:40:38,884 --> 00:40:42,754 Five orbiting galaxy clusters crashed together 636 00:40:42,756 --> 00:40:46,657 in the single biggest cosmic pile-up ever discovered. 637 00:40:52,396 --> 00:40:56,967 Gradually, the five clusters merged and fused 638 00:40:56,969 --> 00:41:00,270 to form a single giant supercluster 639 00:41:00,272 --> 00:41:02,405 6 million light-years across. 640 00:41:04,508 --> 00:41:06,642 The incredible power of orbits 641 00:41:06,644 --> 00:41:11,479 can literally tie the universe in knots. 642 00:41:11,481 --> 00:41:14,515 Structures in the Universe have evolved over billions of years 643 00:41:14,517 --> 00:41:18,051 through their orbits and their mutual gravitational attraction, 644 00:41:18,053 --> 00:41:20,987 and they've built up into larger and larger structures. 645 00:41:20,989 --> 00:41:23,823 And it's all thanks to these same attractive forces 646 00:41:23,825 --> 00:41:26,825 that bring them together but can also tear them apart. 647 00:41:35,633 --> 00:41:37,801 Again and again, 648 00:41:37,803 --> 00:41:41,270 we discover orbits dominating the cosmos. 649 00:41:42,405 --> 00:41:45,040 The atom is the basic unit of chemistry. 650 00:41:45,042 --> 00:41:46,408 In the same way, 651 00:41:46,410 --> 00:41:50,246 the orbit is the basic unit of the Universe itself. 652 00:41:50,248 --> 00:41:52,981 If you understand all possible orbits, 653 00:41:52,983 --> 00:41:56,351 you understand the dynamics driving the Universe. 654 00:41:56,353 --> 00:42:00,688 Orbits have created a cosmos 655 00:42:00,690 --> 00:42:03,591 full of richness and complexity. 656 00:42:03,593 --> 00:42:06,260 Orbits are changeable. They're chaotic. 657 00:42:06,262 --> 00:42:08,696 Things that we never thought were possible 658 00:42:08,698 --> 00:42:09,931 are, in fact, possible. 659 00:42:09,933 --> 00:42:12,601 From the smallest scale to the largest scale, 660 00:42:12,603 --> 00:42:15,503 it's the gravitational interactions and collisions 661 00:42:15,505 --> 00:42:19,072 that actually make our Universe the beautiful place that it is. 662 00:42:19,074 --> 00:42:24,911 And behind it all is a curious paradox. 663 00:42:24,913 --> 00:42:28,047 Extreme orbits mean variations, collisions. 664 00:42:28,049 --> 00:42:30,082 That seems very destructive. 665 00:42:30,084 --> 00:42:32,948 But, also, extreme orbits mean colliding galaxies, 666 00:42:32,950 --> 00:42:36,352 collapsing dust clouds, the very creation of life, 667 00:42:36,354 --> 00:42:37,419 as well as destruction. 668 00:42:37,421 --> 00:42:42,391 Orbits are the driving force 669 00:42:42,393 --> 00:42:47,762 behind this never-ending cycle of creation and destruction. 670 00:42:47,764 --> 00:42:52,633 They're at the very heart of how the Universe works. 671 00:42:52,658 --> 00:42:56,658 == sync, corrected by elderman ==53592

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