1 00:00:01,835 --> 00:00:04,205 (male narrator) The end is coming. 2 00:00:07,375 --> 00:00:12,580 But which cosmic catastrophe will deliver the death blow? 3 00:00:14,782 --> 00:00:16,584 Were the Vikings right to fear 4 00:00:16,617 --> 00:00:19,753 the frozen apocalypse of an endless winter? 5 00:00:21,855 --> 00:00:24,192 Did the Buddhists correctly predict 6 00:00:24,225 --> 00:00:27,161 a fiery end to life on Earth? 7 00:00:29,597 --> 00:00:33,467 Or will the thunderous Christian vision of Armageddon 8 00:00:33,501 --> 00:00:36,537 come crashing down from the stars? 9 00:00:38,639 --> 00:00:42,610 Which ancient prophesy do scientists believe 10 00:00:42,643 --> 00:00:46,614 accurately foretells our doom? 11 00:00:46,647 --> 00:00:49,250 And how close are we... 12 00:00:49,283 --> 00:00:52,786 To the end of the world? 13 00:00:54,755 --> 00:01:00,628 Ancient mysteries, shrouded in the shadows of time. 14 00:01:00,661 --> 00:01:07,301 Now, can they finally be solved by looking to the heavens? 15 00:01:07,335 --> 00:01:12,706 The truth is out there, hidden among the stars 16 00:01:12,740 --> 00:01:17,278 in a place we call... 17 00:01:23,217 --> 00:01:26,887 It's the ultimate fear for every human being on Earth 18 00:01:26,920 --> 00:01:30,558 and across time-- 19 00:01:30,591 --> 00:01:33,627 The end of the world. 20 00:01:33,661 --> 00:01:37,765 A time when death is unescapable, 21 00:01:37,798 --> 00:01:40,268 delivered by fire... 22 00:01:40,301 --> 00:01:42,136 ice... 23 00:01:42,170 --> 00:01:45,573 or terrifying forces from beyond our planet. 24 00:01:47,575 --> 00:01:52,180 Every civilization has its own horrific vision. 25 00:01:54,448 --> 00:01:57,151 (Markley) Every culture knows about death. 26 00:01:57,185 --> 00:01:59,887 Every culture has seen major disasters. 27 00:01:59,920 --> 00:02:02,623 Destruction, death, the ending of things 28 00:02:02,656 --> 00:02:04,758 really looks like it's part of the natural order, 29 00:02:04,792 --> 00:02:06,527 so it shouldn't be a surprise to us 30 00:02:06,560 --> 00:02:09,563 that every culture has an Armageddon scenario. 31 00:02:13,567 --> 00:02:14,802 In a lot of mythologies, 32 00:02:14,835 --> 00:02:17,171 the world ends by either cold or by fire, 33 00:02:17,205 --> 00:02:20,908 the real extremes of weather on the Earth. 34 00:02:20,941 --> 00:02:25,846 (narrator) But which vision of Armageddon does modern science support? 35 00:02:25,879 --> 00:02:29,750 How exactly will the world end? 36 00:02:33,687 --> 00:02:36,224 Could it be the frozen apocalypse, 37 00:02:36,257 --> 00:02:38,626 feared by the Vikings? 38 00:02:41,862 --> 00:02:45,633 It's 535 A.D., 39 00:02:45,666 --> 00:02:47,568 and the people of a Norse village, 40 00:02:47,601 --> 00:02:50,238 so used to harsh winters, 41 00:02:50,271 --> 00:02:54,642 have never seen anything like this. 42 00:02:54,675 --> 00:02:57,911 Even the elders can't recall such a brutal season. 43 00:02:57,945 --> 00:03:03,751 Spring should be here, but the winter won't let go. 44 00:03:03,784 --> 00:03:08,622 Farmers can't plant crops. Livestock is dying. 45 00:03:08,656 --> 00:03:11,792 What if winter never ends? 46 00:03:11,825 --> 00:03:14,762 This truly feels like the beginning 47 00:03:14,795 --> 00:03:18,832 of the end of the world. 48 00:03:18,866 --> 00:03:22,903 It's winters like this that probably inspired 49 00:03:22,936 --> 00:03:26,840 the Norse vision of the apocalypse. 50 00:03:26,874 --> 00:03:33,281 They called it Ragnarok, or the Twilight of the Gods. 51 00:03:33,314 --> 00:03:36,284 Even the doomed pantheon of Norse deities 52 00:03:36,317 --> 00:03:38,919 was powerless to stop it. 53 00:03:38,952 --> 00:03:41,389 It meant the rise of monsters 54 00:03:41,422 --> 00:03:45,826 and the annihilation of gods and men. 55 00:03:45,859 --> 00:03:48,762 It starts with Fimbulwinter, 56 00:03:48,796 --> 00:03:54,902 a killing cold worse than even a hardened Viking could imagine. 57 00:03:54,935 --> 00:03:58,005 (Markley) The Norse believed that the end of the world 58 00:03:58,038 --> 00:04:01,309 would be heralded by a three-year mighty winter, 59 00:04:01,342 --> 00:04:05,045 following which, the heavens and the Earth would be destroyed. 60 00:04:05,078 --> 00:04:10,651 Perpetual winter-- that's the end. 61 00:04:10,684 --> 00:04:13,321 (narrator) Could the end of everything come in cold 62 00:04:13,354 --> 00:04:16,757 as the Norse predicted? 63 00:04:19,960 --> 00:04:22,062 Looking back at our planet's history, 64 00:04:22,095 --> 00:04:26,700 it's not hard to imagine. 65 00:04:26,734 --> 00:04:30,938 Three times in the Earth's past, glaciers may have spread 66 00:04:30,971 --> 00:04:34,575 to encase the entire planet in ice and slush, 67 00:04:34,608 --> 00:04:37,044 like a giant snowball. 68 00:04:40,381 --> 00:04:43,984 Now scientists predict something even more extreme, 69 00:04:44,017 --> 00:04:47,621 an icy apocalypse that will put a deep freeze 70 00:04:47,655 --> 00:04:51,792 not just on Earth, but the entire universe. 71 00:04:54,862 --> 00:04:57,798 And this frigid end was set into motion 72 00:04:57,831 --> 00:05:02,703 at the very beginning... 73 00:05:02,736 --> 00:05:05,706 with the rapid expansion of the universe 74 00:05:05,739 --> 00:05:09,910 after the Big Bang. 75 00:05:09,943 --> 00:05:12,780 (Johnson) We've known for a long time that the universe is expanding, 76 00:05:12,813 --> 00:05:15,583 and it's been cooling down as it expands 77 00:05:15,616 --> 00:05:19,787 since the Big Bang, 13.8 billion years ago. 78 00:05:19,820 --> 00:05:21,689 (narrator) Heat is energy, 79 00:05:21,722 --> 00:05:25,893 and the universe has only so much of it to go around. 80 00:05:25,926 --> 00:05:29,830 As the universe expands, the energy gets diluted, 81 00:05:29,863 --> 00:05:34,101 and everything starts to cool. 82 00:05:34,134 --> 00:05:37,838 Scientists once believed that the expansion of the universe 83 00:05:37,871 --> 00:05:41,074 would eventually slow down, or even reverse 84 00:05:41,108 --> 00:05:46,680 as cosmic gravity tapped the brakes. 85 00:05:46,714 --> 00:05:48,649 But then... 86 00:05:48,682 --> 00:05:52,720 they discovered that some unseen, unexplained force 87 00:05:52,753 --> 00:05:54,788 was out-dueling gravity, 88 00:05:54,822 --> 00:06:00,060 accelerating us toward a truly chilling Armageddon. 89 00:06:02,430 --> 00:06:04,765 (Johnson) In the late '90s, we discovered 90 00:06:04,798 --> 00:06:08,702 that the universe is actually accelerating the expansion. 91 00:06:08,736 --> 00:06:11,739 This has put a new wrinkle on the scenarios 92 00:06:11,772 --> 00:06:15,008 about how the universe might end. 93 00:06:15,042 --> 00:06:17,945 (Alex Filippenko) I was a member of both teams that were studying 94 00:06:17,978 --> 00:06:20,581 the expansion history of the universe, 95 00:06:20,614 --> 00:06:22,416 and when I saw the results, 96 00:06:22,450 --> 00:06:25,753 that the universe is accelerating in its expansion, 97 00:06:25,786 --> 00:06:27,855 I was just completely stunned. 98 00:06:27,888 --> 00:06:29,957 It was a shocking result. 99 00:06:29,990 --> 00:06:32,626 Essentially, no one had expected this. 100 00:06:35,763 --> 00:06:38,131 (narrator) What's out there, stronger than gravity, 101 00:06:38,165 --> 00:06:42,069 that's pulling the universe apart? 102 00:06:42,102 --> 00:06:45,639 Incredibly, nobody knows. 103 00:06:45,673 --> 00:06:51,845 Astronomers simply call it dark energy. 104 00:06:51,879 --> 00:06:55,048 (Johnson) We're still not sure exactly what dark energy is. 105 00:06:55,082 --> 00:06:59,987 It may be an intrinsic energy that space itself has 106 00:07:00,020 --> 00:07:05,192 that actually makes it prefer to get larger. 107 00:07:05,225 --> 00:07:07,961 This rubber band has what we call elasticity. 108 00:07:07,995 --> 00:07:09,963 If I pull on it and make it larger, 109 00:07:09,997 --> 00:07:12,866 it actually tries to pull back 110 00:07:12,900 --> 00:07:15,503 and restore its shape to a smaller size. 111 00:07:15,536 --> 00:07:17,971 Imagine the reverse of that, where instead, 112 00:07:18,005 --> 00:07:21,074 you have something that likes to increase its size. 113 00:07:21,108 --> 00:07:25,646 That's the sort of physics that might underlie dark energy, 114 00:07:25,679 --> 00:07:28,682 where it actually is driving the acceleration 115 00:07:28,716 --> 00:07:32,452 of the whole expansion of the universe. 116 00:07:33,987 --> 00:07:35,155 (narrator) One thing we do know 117 00:07:35,188 --> 00:07:36,990 about the mysterious dark energy 118 00:07:37,024 --> 00:07:41,962 is that it makes up around 70% of the universe. 119 00:07:41,995 --> 00:07:45,933 (Howell) That's crazy, that we don't know about most of the universe. 120 00:07:45,966 --> 00:07:49,236 We're the weird things in the universe. 121 00:07:49,269 --> 00:07:51,972 (narrator) So how will dark energy drive us 122 00:07:52,005 --> 00:07:55,609 toward a frigid cosmic Armageddon? 123 00:07:55,643 --> 00:07:58,712 Little by little, but faster and faster, 124 00:07:58,746 --> 00:08:03,150 it will move everything away from everything else. 125 00:08:03,183 --> 00:08:05,753 And as clusters of galaxies spread, 126 00:08:05,786 --> 00:08:10,924 the expanding universe will get colder. 127 00:08:10,958 --> 00:08:12,760 (Danly) When we look out in the universe, 128 00:08:12,793 --> 00:08:16,229 we see that all galaxies appear to be moving away from us. 129 00:08:18,131 --> 00:08:20,868 (narrator) If we could view the universe from a different galaxy, 130 00:08:20,901 --> 00:08:23,136 we'd see the same thing. 131 00:08:23,170 --> 00:08:25,706 How can all the galaxies be moving 132 00:08:25,739 --> 00:08:28,909 away from all the other galaxies? 133 00:08:28,942 --> 00:08:31,278 (Danly) One way to think about the expanding universe 134 00:08:31,311 --> 00:08:35,082 is to think about an expanding loaf of raisin bread. 135 00:08:35,115 --> 00:08:40,220 The raisins are galaxies, and the dough is the universe. 136 00:08:40,253 --> 00:08:41,855 The raisin bread is expanding 137 00:08:41,889 --> 00:08:43,991 because the baking soda in the bread 138 00:08:44,024 --> 00:08:48,962 is causing it to expand, kind of like dark energy. 139 00:08:48,996 --> 00:08:51,131 (narrator) The baking soda is expanding the dough 140 00:08:51,164 --> 00:08:52,933 and spreading the raisins, 141 00:08:52,966 --> 00:08:55,736 just like dark energy is expanding the universe 142 00:08:55,769 --> 00:09:02,109 and moving all the galaxies farther and farther apart. 143 00:09:02,142 --> 00:09:06,213 As the universe expands, its energy gets diluted. 144 00:09:06,246 --> 00:09:11,118 There won't be enough to build new stars as old ones die. 145 00:09:11,151 --> 00:09:15,689 With no stars to generate heat and no new stars being born, 146 00:09:15,723 --> 00:09:20,227 the universe marches toward a bitterly cold end, 147 00:09:20,260 --> 00:09:23,964 an ice age that affects not just one planet, 148 00:09:23,997 --> 00:09:27,234 but the entire universe. 149 00:09:27,267 --> 00:09:30,604 In a universe that's expanding eternally, 150 00:09:30,638 --> 00:09:32,906 it's getting colder and colder with time. 151 00:09:32,940 --> 00:09:36,944 It's as though you're entering a long, extended-- 152 00:09:36,977 --> 00:09:41,749 Indeed, eternal winter. 153 00:09:41,782 --> 00:09:44,384 (narrator) A Nordic nightmare, 154 00:09:44,417 --> 00:09:48,088 the mighty winter that heralds Armageddon. 155 00:09:51,158 --> 00:09:53,894 But is that truly the end? 156 00:09:53,927 --> 00:09:56,029 Or does dark energy have the power 157 00:09:56,063 --> 00:09:59,733 to do something even more destructive? 158 00:09:59,767 --> 00:10:02,670 It's possible that the mysterious force 159 00:10:02,703 --> 00:10:05,839 could grow stronger over time. 160 00:10:05,873 --> 00:10:08,241 (Filippenko) In that case, eventually, 161 00:10:08,275 --> 00:10:10,377 clusters of galaxies will get ripped apart, 162 00:10:10,410 --> 00:10:12,680 then galaxies will be ripped apart, 163 00:10:12,713 --> 00:10:15,048 then planetary systems will be ripped apart, 164 00:10:15,082 --> 00:10:20,654 planets, us, and even the atoms of which we are made. 165 00:10:22,089 --> 00:10:23,256 (narrator) It won't stop 166 00:10:23,290 --> 00:10:26,794 until nothing's left to tear apart. 167 00:10:26,827 --> 00:10:30,430 Scientists call this "the Big Rip." 168 00:10:30,463 --> 00:10:33,100 (Filippenko) If the Big Rip were to occur, 169 00:10:33,133 --> 00:10:35,168 it would be the ultimate Armageddon. 170 00:10:35,202 --> 00:10:37,404 Everything ripped apart. 171 00:10:37,437 --> 00:10:41,742 Wow, doesn't get any worse than that. 172 00:10:41,775 --> 00:10:44,144 (narrator) The Big Rip is one vision of Armageddon 173 00:10:44,177 --> 00:10:47,815 on a universal scale. 174 00:10:47,848 --> 00:10:52,853 But even if the universe is fated to end in bitter cold, 175 00:10:52,886 --> 00:10:56,724 is the Earth itself destined to die much sooner, 176 00:10:56,757 --> 00:11:00,660 not in cold, but fire? 177 00:11:06,066 --> 00:11:09,269 (narrator) Ancient prophesies foretell Armageddon, 178 00:11:09,302 --> 00:11:17,010 but few agree how it will come to pass. 179 00:11:17,044 --> 00:11:21,715 The ancient Norse predicted the beginning of the end 180 00:11:21,749 --> 00:11:24,718 in bone-cracking cold, 181 00:11:24,752 --> 00:11:27,254 a prophecy that our expanding universe 182 00:11:27,287 --> 00:11:31,124 might make happen. 183 00:11:31,158 --> 00:11:37,731 The Norse weren't the only ones to fear a wintery Armageddon. 184 00:11:41,168 --> 00:11:46,273 It's the 16th century, in what is now Mexico. 185 00:11:48,942 --> 00:11:51,879 A prisoner captured from a recent battle 186 00:11:51,912 --> 00:11:56,316 is dragged out and held down on a slab. 187 00:11:56,349 --> 00:12:00,153 The Aztec priest raises an obsidian knife 188 00:12:00,187 --> 00:12:02,422 and slices open the prisoner's chest... 189 00:12:02,455 --> 00:12:04,157 Aah! 190 00:12:04,191 --> 00:12:06,894 (narrator) Ripping out the still-beating heart 191 00:12:06,927 --> 00:12:11,064 and raising it triumphantly to the sun. 192 00:12:11,098 --> 00:12:16,369 He holds the fate of the planet in his bloodstained hands. 193 00:12:16,403 --> 00:12:19,139 The Aztecs believed they had a duty 194 00:12:19,172 --> 00:12:22,542 to feed the sun through blood sacrifice, 195 00:12:22,575 --> 00:12:25,312 giving it the strength to make its daily journey 196 00:12:25,345 --> 00:12:29,416 across the sky. 197 00:12:29,449 --> 00:12:31,484 If they failed to feed it, 198 00:12:31,518 --> 00:12:36,489 they believed it would disappear. 199 00:12:40,060 --> 00:12:42,529 But what would really happen 200 00:12:42,562 --> 00:12:47,334 if one dark morning, the sun vanished? 201 00:12:47,367 --> 00:12:51,204 (Filippenko) If the sun were to suddenly disappear from the universe, 202 00:12:51,238 --> 00:12:53,340 then there'd be no gravity pulling the Earth 203 00:12:53,373 --> 00:12:55,508 toward the sun anymore, and that means 204 00:12:55,542 --> 00:12:58,478 that the Earth would go flying off in space 205 00:12:58,511 --> 00:13:00,113 in a straight line 206 00:13:00,147 --> 00:13:02,515 along the direction it was moving 207 00:13:02,549 --> 00:13:06,319 at the instant that the sun disappeared. 208 00:13:06,353 --> 00:13:10,824 (narrator) This would doom the Earth to a frozen Armageddon 209 00:13:10,858 --> 00:13:15,028 that recalls the deadly Norse winter. 210 00:13:15,062 --> 00:13:18,565 Fortunately for us, our sun won't magically vanish, 211 00:13:18,598 --> 00:13:20,533 but what it will do is evolve. 212 00:13:23,003 --> 00:13:28,141 (narrator) Evolve...and then die. 213 00:13:28,175 --> 00:13:33,246 Will this mean a cold, dark death for the Earth, 214 00:13:33,280 --> 00:13:34,581 or something more like 215 00:13:34,614 --> 00:13:38,485 the ancient Buddhists envisioned? 216 00:13:38,518 --> 00:13:40,087 In the Buddhist apocalypse, 217 00:13:40,120 --> 00:13:45,325 seven suns will blaze across the sky. 218 00:13:45,358 --> 00:13:47,394 When the sixth sun rises, 219 00:13:47,427 --> 00:13:50,563 it will bake the Earth like pottery. 220 00:13:50,597 --> 00:13:55,168 Then, according to the prophesy, "A seventh sun appears. 221 00:13:55,202 --> 00:13:57,938 "The mountains fire and blaze, 222 00:13:57,971 --> 00:14:00,941 "and of this great earth, when consumed, 223 00:14:00,974 --> 00:14:05,979 neither ashes nor soot remains." 224 00:14:09,082 --> 00:14:12,252 Although there aren't multiple suns in our future, 225 00:14:12,285 --> 00:14:16,990 were the Buddhists right that Earth will die by fire? 226 00:14:17,024 --> 00:14:23,030 Will we be burned into oblivion by our dying sun? 227 00:14:23,063 --> 00:14:27,434 At 5 billion years old, the sun has reached middle age 228 00:14:27,467 --> 00:14:30,170 and its days are numbered. 229 00:14:30,203 --> 00:14:35,108 Scientists have a clear idea of how it will die, 230 00:14:35,142 --> 00:14:40,914 and it's all driven by pressure. 231 00:14:40,948 --> 00:14:43,150 The heat of nuclear fusion in the core 232 00:14:43,183 --> 00:14:45,352 creates enormous outward pressure 233 00:14:45,385 --> 00:14:47,454 that should blow the sun apart, 234 00:14:47,487 --> 00:14:49,022 but instead, it's countered 235 00:14:49,056 --> 00:14:53,460 by the equal force of gravity pushing in. 236 00:14:56,463 --> 00:14:59,933 Balancing inward and outward pressure 237 00:14:59,967 --> 00:15:04,171 is something every diver stakes his life on. 238 00:15:04,204 --> 00:15:06,106 (Howell) The reason we have life on earth 239 00:15:06,139 --> 00:15:08,441 is because the sun is burning through its nuclear fuel. 240 00:15:08,475 --> 00:15:10,443 it's an equilibrium. 241 00:15:10,477 --> 00:15:13,413 It's a balance between gravity trying to crush it down 242 00:15:13,446 --> 00:15:16,316 and pressure holding it up. 243 00:15:16,349 --> 00:15:20,988 (narrator) So what happens when equilibrium is lost? 244 00:15:21,021 --> 00:15:22,455 On the surface of the Earth, 245 00:15:22,489 --> 00:15:27,160 human beings are in equilibrium, just like the sun. 246 00:15:27,194 --> 00:15:31,364 The atmosphere presses on us at 15 pounds per square inch, 247 00:15:31,398 --> 00:15:34,267 or one atmosphere. 248 00:15:34,301 --> 00:15:36,736 We don't feel it because the air inside us 249 00:15:36,769 --> 00:15:40,307 is pushing out at the same pressure. 250 00:15:43,043 --> 00:15:45,478 But take an object designed to be in equilibrium 251 00:15:45,512 --> 00:15:49,349 on the surface, and bring it underwater, 252 00:15:49,382 --> 00:15:51,451 and you start to see what happens 253 00:15:51,484 --> 00:15:55,055 when equilibrium is lost. 254 00:15:55,088 --> 00:15:56,323 (Howell) I want to demonstrate 255 00:15:56,356 --> 00:16:00,193 what a small amount of atmospheric pressure 256 00:16:00,227 --> 00:16:04,297 can do to this metal can. 257 00:16:04,331 --> 00:16:07,267 As we're descending, 258 00:16:07,300 --> 00:16:11,238 we're already seeing effects of this can. 259 00:16:11,271 --> 00:16:13,373 Check it out. 260 00:16:13,406 --> 00:16:20,147 The can is starting to bend, and we're only at 15 feet. 261 00:16:20,180 --> 00:16:24,217 I'm pretty surprised that we're starting to see 262 00:16:24,251 --> 00:16:28,455 the effects of pressure at only 15 feet. 263 00:16:28,488 --> 00:16:31,158 I dive 15 feet all the time, and I didn't know 264 00:16:31,191 --> 00:16:35,428 I was exerting these kinds of forces on my body. 265 00:16:36,763 --> 00:16:40,167 Now we're finally at 33 feet. 266 00:16:40,200 --> 00:16:43,070 That's double atmospheric pressure. 267 00:16:43,103 --> 00:16:46,606 We totally crushed our can. 268 00:16:46,639 --> 00:16:49,142 It's pretty obvious that when you have 269 00:16:49,176 --> 00:16:52,312 twice the amount of pressure on the outside of the can, 270 00:16:52,345 --> 00:16:58,218 what's on the inside, our can, just can't survive. 271 00:16:58,251 --> 00:17:02,655 (narrator) So what will drive the sun out of equilibrium? 272 00:17:02,689 --> 00:17:07,460 And what will this mean for our planet? 273 00:17:07,494 --> 00:17:10,363 (Lucianne Walkowicz) The sun's lifetime is mostly governed 274 00:17:10,397 --> 00:17:13,066 by how much fuel it has in its core 275 00:17:13,100 --> 00:17:16,069 versus the force of gravity of its own matter 276 00:17:16,103 --> 00:17:17,604 pushing inward. 277 00:17:17,637 --> 00:17:19,772 Over time, stars like our sun, 278 00:17:19,806 --> 00:17:23,210 which fuse hydrogen into helium in their cores, 279 00:17:23,243 --> 00:17:26,146 eventually start to run out of fuel, and enter 280 00:17:26,179 --> 00:17:29,382 a period of time where they go through these death throes. 281 00:17:29,416 --> 00:17:31,684 (narrator) As the sun runs out of fuel, 282 00:17:31,718 --> 00:17:35,188 gravity will keep pulling the core tighter. 283 00:17:35,222 --> 00:17:36,623 But as the core shrinks, 284 00:17:36,656 --> 00:17:39,326 it will heat the surrounding layers of gas, 285 00:17:39,359 --> 00:17:44,231 causing hydrogen and helium to fuse even faster than before. 286 00:17:44,264 --> 00:17:47,200 The extra energy released will increase the pressure 287 00:17:47,234 --> 00:17:50,203 on the outer layer of the sun. 288 00:17:50,237 --> 00:17:54,541 (Filippenko) That extra energy will push on the outer layers of the sun, 289 00:17:54,574 --> 00:17:58,411 causing them to expand, becoming big. 290 00:17:58,445 --> 00:18:00,413 We call this a red giant. 291 00:18:02,349 --> 00:18:04,217 (narrator) The core will keep contracting 292 00:18:04,251 --> 00:18:08,488 while its outer layer grows bigger and brighter. 293 00:18:08,521 --> 00:18:11,458 (Filippenko) The sun will become so bright and so big 294 00:18:11,491 --> 00:18:13,893 that the Earth might actually find itself 295 00:18:13,926 --> 00:18:16,429 inside the sun for a while. 296 00:18:16,463 --> 00:18:18,231 That would be Armageddon. 297 00:18:19,666 --> 00:18:22,302 (narrator) The Earth will be incinerated, 298 00:18:22,335 --> 00:18:28,641 lifeless, but still a planet after the sun gradually cools. 299 00:18:28,675 --> 00:18:31,511 (Filippenko) The sun will fade away, 300 00:18:31,544 --> 00:18:34,281 and then the Earth will just keep on orbiting 301 00:18:34,314 --> 00:18:41,654 a very dim, ever dimmer lump that remains from today's sun. 302 00:18:43,656 --> 00:18:48,595 (narrator) The dying sun will trigger our own infernal Armageddon, 303 00:18:48,628 --> 00:18:55,335 a blazing, Buddhist finale before eternal Aztec winter. 304 00:18:55,368 --> 00:18:57,937 Or life on Earth could be finished 305 00:18:57,970 --> 00:19:00,173 long before that happens, 306 00:19:00,207 --> 00:19:03,710 and much, much sooner than we expect. 307 00:19:09,582 --> 00:19:11,651 (narrator) Ancient visions predict 308 00:19:11,684 --> 00:19:16,656 that Armageddon is inevitable some distant day. 309 00:19:18,991 --> 00:19:23,696 But what if our day of reckoning... 310 00:19:23,730 --> 00:19:27,300 Is today? 311 00:19:29,269 --> 00:19:33,406 Chelyabinsk, Russia, February, 2013. 312 00:19:36,343 --> 00:19:38,611 Residents see a fireball 313 00:19:38,645 --> 00:19:43,616 blaze across the sky, seconds before it detonates. 314 00:19:43,650 --> 00:19:46,419 [boom] 315 00:19:46,453 --> 00:19:49,422 [glass breaking and car alarms blaring] 316 00:19:51,691 --> 00:19:56,429 The asteroid arrives unannounced... 317 00:19:56,463 --> 00:19:59,399 leaving no time to react or take cover. 318 00:19:59,432 --> 00:20:01,834 [boom] 319 00:20:01,868 --> 00:20:03,836 (Howell) It exploded in the atmosphere 320 00:20:03,870 --> 00:20:07,540 with a force about 20 times greater 321 00:20:07,574 --> 00:20:11,778 than the atomic bomb dropped on Hiroshima. 322 00:20:11,811 --> 00:20:14,281 Luckily, it was high enough in the atmosphere 323 00:20:14,314 --> 00:20:16,416 that the atmosphere absorbed most of the energy. 324 00:20:16,449 --> 00:20:18,385 [boom] 325 00:20:20,587 --> 00:20:24,524 (Filippenko) That object was only about 20 yards in diameter. 326 00:20:24,557 --> 00:20:26,293 That was a small rock, 327 00:20:26,326 --> 00:20:28,861 yet the explosion caused widespread damage, 328 00:20:28,895 --> 00:20:33,633 lots of imploding glass that actually hurt 1,500 people, 329 00:20:33,666 --> 00:20:35,602 many buildings damaged. 330 00:20:37,804 --> 00:20:41,308 (narrator) A larger asteroid or comet 331 00:20:41,341 --> 00:20:47,580 could cause mass extinction on Earth... 332 00:20:47,614 --> 00:20:51,951 leaving the planet intact, but lifeless. 333 00:20:56,589 --> 00:20:59,759 The idea of an Earth devoid of people 334 00:20:59,792 --> 00:21:02,662 is something the ancients feared. 335 00:21:02,695 --> 00:21:04,997 (Markley) When they talk about Armageddon scenarios, 336 00:21:05,031 --> 00:21:07,467 it's wiping away the living organisms 337 00:21:07,500 --> 00:21:09,869 that are here now and starting again. 338 00:21:09,902 --> 00:21:12,339 At least that's the usual scenario. 339 00:21:12,372 --> 00:21:16,576 So the world will still be here, the heavens will still be there. 340 00:21:16,609 --> 00:21:20,313 We won't. 341 00:21:20,347 --> 00:21:22,549 (narrator) But the Ancients had different visions 342 00:21:22,582 --> 00:21:26,853 of how humanity would be wiped out. 343 00:21:26,886 --> 00:21:30,623 Muslim writings foresaw the end of the world, 344 00:21:30,657 --> 00:21:33,693 signaled by landslides 345 00:21:33,726 --> 00:21:37,564 and a cloud of smoke... 346 00:21:37,597 --> 00:21:42,435 engulfing the planet. 347 00:21:42,469 --> 00:21:48,375 The Romans envisioned Armageddon by fire or flood--or both-- 348 00:21:48,408 --> 00:21:52,445 when the time comes to cleanse the Earth. 349 00:21:52,479 --> 00:21:55,982 The Roman philosopher Seneca wrote, 350 00:21:56,015 --> 00:21:58,985 "Water and fire bring about creation, 351 00:21:59,018 --> 00:22:01,120 "they bring about destruction, 352 00:22:01,153 --> 00:22:03,556 "so when the world decides to change, 353 00:22:03,590 --> 00:22:06,426 "it sends the sea crashing down on us, 354 00:22:06,459 --> 00:22:10,530 or causes extinction by heat and fire." 355 00:22:10,563 --> 00:22:13,366 (Markley) This sounds a lot like the kind of thing you would get 356 00:22:13,400 --> 00:22:15,868 when you got a meteorite slamming into the oceans, 357 00:22:15,902 --> 00:22:19,138 a global tsunami, nuclear winter, 358 00:22:19,171 --> 00:22:21,674 the end of the world. 359 00:22:21,708 --> 00:22:24,744 (narrator) Perhaps the most frightening vision of Armageddon 360 00:22:24,777 --> 00:22:28,415 comes from Christianity. 361 00:22:28,448 --> 00:22:32,452 The Book of Revelation describes all manner of destruction 362 00:22:32,485 --> 00:22:36,122 raining down on Earth. 363 00:22:36,155 --> 00:22:39,058 "And there were voices, and thunders, and lightnings; 364 00:22:39,091 --> 00:22:42,028 "and there was a great earthquake, 365 00:22:42,061 --> 00:22:46,065 "not seen since men were upon the Earth. 366 00:22:46,098 --> 00:22:49,168 "He maketh fire come down from heaven, 367 00:22:49,201 --> 00:22:56,075 and the sun became black, and the moon became as blood." 368 00:22:58,711 --> 00:23:00,913 It's a terrifying vision, 369 00:23:00,947 --> 00:23:07,086 but can such a global cataclysm really happen? 370 00:23:09,188 --> 00:23:11,458 (Markley) The Christian scenario for the end of the world 371 00:23:11,491 --> 00:23:17,864 involves raging seas, famine, pestilence, fire, earthquakes. 372 00:23:17,897 --> 00:23:19,599 These are all of the kind of things 373 00:23:19,632 --> 00:23:22,201 that you could have if you were suffering multiple impacts. 374 00:23:22,234 --> 00:23:25,672 Perhaps multiple meteorites, a comet that's fragmented 375 00:23:25,705 --> 00:23:27,907 and slammed into the Earth. 376 00:23:27,940 --> 00:23:31,077 This kind of thing could easily happen in real life. 377 00:23:33,680 --> 00:23:39,151 (Howell) With an asteroid impact, there's all kinds of other side effects. 378 00:23:39,185 --> 00:23:41,721 The Earth could get increased vulcanism, 379 00:23:41,754 --> 00:23:46,759 increased earthquakes, the ocean could acidify. 380 00:23:46,793 --> 00:23:49,195 (narrator) Anything not killed immediately 381 00:23:49,228 --> 00:23:52,899 might die slowly. 382 00:23:52,932 --> 00:23:56,603 (Filippenko) The entire food chain would be disrupted. 383 00:23:56,636 --> 00:24:00,740 Many or most species of life on Earth would perish-- 384 00:24:00,773 --> 00:24:06,646 a global mass extinction, a real Armageddon. 385 00:24:09,181 --> 00:24:12,719 (narrator) The sudden meteorite explosion in Chelyabinsk 386 00:24:12,752 --> 00:24:15,555 put the world on notice. 387 00:24:15,588 --> 00:24:18,891 (Filippenko) There are a lot of asteroids and other big rocks 388 00:24:18,925 --> 00:24:21,628 in the solar system just kind of flying around, 389 00:24:21,661 --> 00:24:26,899 and most of them are between the orbits of Mars and Jupiter, 390 00:24:26,933 --> 00:24:30,136 but some of them cross Earth's orbit, 391 00:24:30,169 --> 00:24:35,808 and so eventually, they can slam into the Earth. 392 00:24:35,842 --> 00:24:38,578 [huge explosion] 393 00:24:38,611 --> 00:24:43,215 (narrator) How do we know? 394 00:24:43,249 --> 00:24:48,087 Earth's battered past is carved into the face of the moon. 395 00:24:52,659 --> 00:24:56,529 (Howell) Over the Earth's history, it's been bombarded by meteors, 396 00:24:56,563 --> 00:25:00,166 and one way we can tell is just by looking at the moon. 397 00:25:00,199 --> 00:25:03,169 There are craters everywhere, and they aren't eroded 398 00:25:03,202 --> 00:25:06,238 by the water and the air like they are on the Earth, 399 00:25:06,272 --> 00:25:08,675 so you can look up and see a fossil record 400 00:25:08,708 --> 00:25:13,312 of all of the impacts near Earth. 401 00:25:13,345 --> 00:25:16,649 (narrator) Most scientists believe that an asteroid or comet 402 00:25:16,683 --> 00:25:18,651 measuring 6 miles across 403 00:25:18,685 --> 00:25:23,155 killed off the dinosaurs 65 million years ago, 404 00:25:23,189 --> 00:25:27,226 but few people realize that wasn't the biggest impact 405 00:25:27,259 --> 00:25:31,731 to ever strike the Earth. 406 00:25:34,233 --> 00:25:38,771 In what is now South Africa, an asteroid slams into the Earth 407 00:25:38,805 --> 00:25:43,175 at around 33,000 miles per hour, 408 00:25:43,209 --> 00:25:48,581 blowing out a crater almost the size of Connecticut. 409 00:25:48,615 --> 00:25:50,316 2 billion years later, 410 00:25:50,349 --> 00:25:55,688 the Vredefort Impact Crater remains to tell the tale. 411 00:25:55,722 --> 00:25:58,257 Luckily, that happened billions of years ago, 412 00:25:58,290 --> 00:26:02,629 but if one were to happen today, it would end all life on Earth. 413 00:26:07,900 --> 00:26:11,671 (narrator) Is there another large rock out there, 414 00:26:11,704 --> 00:26:13,339 hurtling through space 415 00:26:13,372 --> 00:26:16,275 with Armageddon written all over it? 416 00:26:16,308 --> 00:26:18,277 Probably. 417 00:26:18,310 --> 00:26:21,047 And if an asteroid doesn't get us, 418 00:26:21,080 --> 00:26:23,716 we might find ourselves in the crosshairs 419 00:26:23,750 --> 00:26:26,118 of a deep-space death beam. 420 00:26:31,724 --> 00:26:33,259 (narrator) The Christian vision of Armageddon 421 00:26:33,292 --> 00:26:37,697 foretells a worldwide apocalypse delivered in thunder, 422 00:26:37,730 --> 00:26:42,835 earthquakes, fire, and brimstone. 423 00:26:42,869 --> 00:26:45,805 And frighteningly, modern science thinks 424 00:26:45,838 --> 00:26:47,940 this kind of global cataclysm 425 00:26:47,974 --> 00:26:51,811 could actually be in Earth's future, 426 00:26:51,844 --> 00:26:55,682 delivered by a single event-- 427 00:26:55,715 --> 00:27:00,720 the impact of a near-earth asteroid. 428 00:27:04,724 --> 00:27:06,158 (Walkowicz) The discovery of near Earth asteroids 429 00:27:06,192 --> 00:27:08,728 is a major priority-- 430 00:27:08,761 --> 00:27:11,864 not only for scientists, but also for our government-- 431 00:27:11,898 --> 00:27:14,767 where we'd like to know how many are out there, 432 00:27:14,801 --> 00:27:18,705 how big they are, and how likely they are to impact Earth. 433 00:27:21,073 --> 00:27:25,044 (narrator) Spotting a threatening asteroid is one thing. 434 00:27:25,077 --> 00:27:29,916 Heading off asteroid Armageddon is another. 435 00:27:29,949 --> 00:27:33,686 (Filippenko) Detecting an asteroid days or hours before it hits 436 00:27:33,720 --> 00:27:38,024 doesn't give us many choices for deflecting it. 437 00:27:38,057 --> 00:27:42,929 We need a long time scale. We need early detection. 438 00:27:42,962 --> 00:27:46,432 That's the key. 439 00:27:46,465 --> 00:27:48,701 (narrator) If we can intercept the asteroid 440 00:27:48,735 --> 00:27:50,236 in time, we might be able 441 00:27:50,269 --> 00:27:54,240 to gently nudge it out of the way with rockets, 442 00:27:54,273 --> 00:27:59,178 or, as some suggest, sunbeams... 443 00:27:59,211 --> 00:28:03,983 and a well-aimed paintball. 444 00:28:04,016 --> 00:28:08,721 Just as dark rooftops in the sun get hotter than light ones, 445 00:28:08,755 --> 00:28:12,124 changing an asteroid's color can change its temperature 446 00:28:12,158 --> 00:28:14,994 and its direction. 447 00:28:15,027 --> 00:28:17,930 (Filippenko) By painting it either with white or silver paint 448 00:28:17,964 --> 00:28:22,735 or with a very dark black paint, that changes the degree 449 00:28:22,769 --> 00:28:27,239 to which light from the sun is either reflected or absorbed. 450 00:28:27,273 --> 00:28:29,809 That will ever so slightly change 451 00:28:29,842 --> 00:28:32,745 the trajectory of the asteroid. 452 00:28:32,779 --> 00:28:35,514 Whenever you reflect light or absorb light, 453 00:28:35,547 --> 00:28:39,018 that changes the motion of the object 454 00:28:39,051 --> 00:28:43,355 that's reflecting or absorbing the light. 455 00:28:43,389 --> 00:28:45,992 (narrator) With vigilance and technology, 456 00:28:46,025 --> 00:28:49,762 we might be able to avert Armageddon, 457 00:28:49,796 --> 00:28:54,166 at least for a while. 458 00:28:54,200 --> 00:28:56,402 But asteroids aren't the only threat 459 00:28:56,435 --> 00:28:59,972 that can destroy the planet without warning. 460 00:29:03,175 --> 00:29:06,112 (narrator) On April 27, 2013, 461 00:29:06,145 --> 00:29:09,248 scientists at observatories around the world 462 00:29:09,281 --> 00:29:13,119 are shocked when NASA's Swift satellite 463 00:29:13,152 --> 00:29:17,489 detects a monstrous dagger of deadly radiation 464 00:29:17,523 --> 00:29:22,061 hurtling through space near the speed of light. 465 00:29:22,094 --> 00:29:24,163 It's a gamma ray burst, 466 00:29:24,196 --> 00:29:27,566 a death beam for anything in its path, 467 00:29:27,599 --> 00:29:30,102 and this one was closer to the Earth 468 00:29:30,136 --> 00:29:34,206 than anyone had ever seen. 469 00:29:35,541 --> 00:29:38,244 All light, whether it's lamp light, 470 00:29:38,277 --> 00:29:41,948 infrared light, radio waves, or X-rays, 471 00:29:41,981 --> 00:29:45,284 are part of the electromagnetic spectrum. 472 00:29:45,317 --> 00:29:48,087 Gamma rays are a kind of high-energy light 473 00:29:48,120 --> 00:29:53,192 that's much, much stronger than X-rays. 474 00:29:53,225 --> 00:29:56,428 (Filippenko) Gamma ray bursts are thought to release more energy 475 00:29:56,462 --> 00:29:59,165 than any other single events in the universe 476 00:29:59,198 --> 00:30:01,133 other than the Big Bang, 477 00:30:01,167 --> 00:30:02,969 the birth of the universe itself. 478 00:30:03,002 --> 00:30:08,040 They release gargantuan amounts of energy. 479 00:30:08,074 --> 00:30:11,844 (Johnson) It's interesting to speculate about what must be happening 480 00:30:11,878 --> 00:30:15,047 to any habitable planets that are in the neighborhood 481 00:30:15,081 --> 00:30:16,949 of such gamma ray bursts. 482 00:30:16,983 --> 00:30:20,619 They must be bathed in a huge amount of gamma radiation, 483 00:30:20,652 --> 00:30:22,621 which means that probably it would be 484 00:30:22,654 --> 00:30:26,458 somewhat cataclysmic for life neighboring such an event. 485 00:30:33,032 --> 00:30:37,436 (narrator) So far, it appears the Earth has been mainly spared, 486 00:30:37,469 --> 00:30:42,141 or at least dodged the worst of it. 487 00:30:42,174 --> 00:30:45,277 (Howell) We see gamma ray bursts at a rate of about one a day 488 00:30:45,311 --> 00:30:48,447 in the universe, and sometimes, they're so powerful, 489 00:30:48,480 --> 00:30:52,151 they even affect the Earth's atmosphere. 490 00:30:52,184 --> 00:30:53,585 (Filippenko) They can be seen easily 491 00:30:53,619 --> 00:30:55,888 from billions of light years away, 492 00:30:55,922 --> 00:30:59,225 and if the jet is pointing toward Earth 493 00:30:59,258 --> 00:31:02,194 and the gamma ray burst is sufficiently nearby, 494 00:31:02,228 --> 00:31:06,065 then that can spell doom for much of life on Earth. 495 00:31:09,101 --> 00:31:14,206 (narrator) What could cause these megablasts? 496 00:31:14,240 --> 00:31:17,944 (Filippenko) Gamma ray bursts are thought to be 497 00:31:17,977 --> 00:31:22,481 hyper-energetic explosions of extremely massive stars. 498 00:31:24,583 --> 00:31:28,620 (narrator) When these massive, spinning stars suddenly collapse, 499 00:31:28,654 --> 00:31:34,393 their last gasp is a gamma ray burst. 500 00:31:36,628 --> 00:31:39,098 Gamma ray bursts get their enormous energy 501 00:31:39,131 --> 00:31:40,666 ultimately from gravity. 502 00:31:40,699 --> 00:31:43,635 A gravity well like this one can help us understand 503 00:31:43,669 --> 00:31:47,406 what's happening on the inside of massive stars when they die. 504 00:31:47,439 --> 00:31:49,508 The shape of this gravity well 505 00:31:49,541 --> 00:31:51,577 illustrates the strength of gravity 506 00:31:51,610 --> 00:31:54,546 around the central mass of a star. 507 00:31:54,580 --> 00:31:58,684 When material falls into a collapsing, massive star, 508 00:31:58,717 --> 00:32:02,154 it spirals around until it finally falls 509 00:32:02,188 --> 00:32:05,457 into the center, forming a black hole. 510 00:32:05,491 --> 00:32:08,194 As it does this, enormous jets of energy 511 00:32:08,227 --> 00:32:12,031 are released as a gamma ray burst. 512 00:32:12,064 --> 00:32:17,436 (narrator) Where that gamma beam points is like a game of Russian roulette, 513 00:32:17,469 --> 00:32:23,542 and if the beam strikes Earth, it's game over. 514 00:32:23,575 --> 00:32:28,080 It might be the most agonizing Armageddon of them all. 515 00:32:34,586 --> 00:32:37,189 (narrator) The ancients have foreseen Armageddon 516 00:32:37,223 --> 00:32:41,227 in all its terrible guises-- 517 00:32:41,260 --> 00:32:44,430 by fire or water, 518 00:32:44,463 --> 00:32:49,135 by ice... or cataclysm. 519 00:32:49,168 --> 00:32:55,241 But gamma ray bursts defy even their vivid imaginations. 520 00:32:55,274 --> 00:32:56,708 The deep space death beam 521 00:32:56,742 --> 00:33:00,746 can strike the Earth without warning. 522 00:33:02,514 --> 00:33:07,053 When a massive star explodes as a gamma ray burst, 523 00:33:07,086 --> 00:33:09,621 a lot of the energy gets channeled 524 00:33:09,655 --> 00:33:13,225 along the axis of rotation of that spinning star. 525 00:33:13,259 --> 00:33:17,029 Now, the axis can point in any random direction, 526 00:33:17,063 --> 00:33:20,632 but if it happens to point toward the Earth, 527 00:33:20,666 --> 00:33:23,102 then the energetic charged particles 528 00:33:23,135 --> 00:33:25,304 and the electromagnetic radiation 529 00:33:25,337 --> 00:33:26,505 blast into the Earth, 530 00:33:26,538 --> 00:33:29,608 causing potentially damaging effects. 531 00:33:31,810 --> 00:33:34,413 (narrator) Driving in our cars, 532 00:33:34,446 --> 00:33:36,815 walking in the park, 533 00:33:36,848 --> 00:33:39,485 we probably wouldn't hear a thing 534 00:33:39,518 --> 00:33:42,388 when the gamma ray strikes our atmosphere 535 00:33:42,421 --> 00:33:46,092 and annihilates it. 536 00:33:46,125 --> 00:33:49,528 But once the Earth's protective ozone layer is gone, 537 00:33:49,561 --> 00:33:56,368 so are we, as death spreads slowly over the globe. 538 00:33:56,402 --> 00:33:59,238 (Filippenko) The side of the Earth facing the gamma ray burst 539 00:33:59,271 --> 00:34:00,839 would have a radiation blast 540 00:34:00,872 --> 00:34:03,409 that could kill animals and plants, 541 00:34:03,442 --> 00:34:05,211 and over the long run, 542 00:34:05,244 --> 00:34:09,248 the loss or severe depletion of the ozone layer could let in 543 00:34:09,281 --> 00:34:12,518 a lot of the ultraviolet radiation from the sun, 544 00:34:12,551 --> 00:34:17,589 leading to damaging effects and loss of life. 545 00:34:20,192 --> 00:34:23,362 (narrator) The more scientists search the skies, 546 00:34:23,395 --> 00:34:27,099 the more they locate hazards that could fulfill-- 547 00:34:27,133 --> 00:34:31,537 or surpass--ancient visions of Armageddon. 548 00:34:36,308 --> 00:34:41,313 From stars that explode... 549 00:34:41,347 --> 00:34:44,350 to objects like this-- 550 00:34:44,383 --> 00:34:49,888 rogue planets careening through space. 551 00:34:49,921 --> 00:34:53,359 We used to think that all planets circled stars, 552 00:34:53,392 --> 00:34:57,396 which kept them bound to a particular spot in the galaxy. 553 00:34:57,429 --> 00:35:02,201 It was reassuring, but wrong. 554 00:35:02,234 --> 00:35:06,372 Scientists have recently started discovering rogue planets, 555 00:35:06,405 --> 00:35:08,840 wandering aimlessly through space, 556 00:35:08,874 --> 00:35:13,445 unleashed from any star's gravitational field. 557 00:35:13,479 --> 00:35:16,415 There are more out there than we ever imagined, 558 00:35:16,448 --> 00:35:19,918 hiding in plain sight. 559 00:35:19,951 --> 00:35:21,653 (Walkowicz) We know that there's a population of planets 560 00:35:21,687 --> 00:35:25,891 out there that exist without orbiting a parent star. 561 00:35:25,924 --> 00:35:28,260 Because there's no light from the parent star, 562 00:35:28,294 --> 00:35:30,929 and we can't use the parent star to indirectly detect 563 00:35:30,962 --> 00:35:36,202 these planets, that makes them very difficult to find. 564 00:35:36,235 --> 00:35:38,770 (narrator) Maybe we need to look harder. 565 00:35:41,573 --> 00:35:44,510 As a rogue planet wanders into our solar system, 566 00:35:44,543 --> 00:35:47,913 its gravitational pull could disrupt the Earth's orbit, 567 00:35:47,946 --> 00:35:53,319 slowing it down, speeding it up, or changing its shape. 568 00:35:53,352 --> 00:35:57,389 That could affect the seasons and the climate, 569 00:35:57,423 --> 00:36:01,927 endangering life on Earth. 570 00:36:05,697 --> 00:36:08,667 (Filippenko) We now think that there could easily be 571 00:36:08,700 --> 00:36:11,870 as many rogue planets in our Milky Way Galaxy 572 00:36:11,903 --> 00:36:13,405 as there are stars, 573 00:36:13,439 --> 00:36:17,276 and perhaps many, many more rogue planets, 574 00:36:17,309 --> 00:36:19,578 ten or hundred or a thousand times 575 00:36:19,611 --> 00:36:24,550 as many rogue planets as there are stars. 576 00:36:24,583 --> 00:36:25,984 (narrator) That's an ominous discovery 577 00:36:26,017 --> 00:36:29,888 that makes our galaxy a bit more crowded, and maybe 578 00:36:29,921 --> 00:36:34,460 a little more dangerous to our planet's survival. 579 00:36:34,493 --> 00:36:36,662 (Filippenko) If there are way more rogue planets 580 00:36:36,695 --> 00:36:39,231 than there are stars in our galaxy, 581 00:36:39,265 --> 00:36:42,000 then the chances that they will come 582 00:36:42,033 --> 00:36:45,271 and gravitationally interact with our solar system 583 00:36:45,304 --> 00:36:48,374 are greater. 584 00:36:48,407 --> 00:36:49,908 (Walkowicz) Fortunately for us, 585 00:36:49,941 --> 00:36:53,645 the galaxy is still very, very sparsely populated. 586 00:36:53,679 --> 00:36:55,747 Everything is very far apart, 587 00:36:55,781 --> 00:36:59,251 and so it's almost diminishingly small chances 588 00:36:59,285 --> 00:37:01,553 that you would have one of these dark planets 589 00:37:01,587 --> 00:37:05,557 entering our solar system. 590 00:37:05,591 --> 00:37:10,462 (narrator) But in 2014, just on the edge of our solar system, 591 00:37:10,496 --> 00:37:14,600 the closest rogue planet was found to date. 592 00:37:14,633 --> 00:37:18,904 It's out there, 80 times further from the sun than we are, 593 00:37:18,937 --> 00:37:22,441 which isn't very far at all. 594 00:37:22,474 --> 00:37:24,343 That's the bad news. 595 00:37:24,376 --> 00:37:27,045 The good news, if you can think of it that way, 596 00:37:27,078 --> 00:37:30,882 is that another, much larger and more distant rogue planet 597 00:37:30,916 --> 00:37:36,288 is holding it safely in its gravitational grip. 598 00:37:37,989 --> 00:37:40,892 Knowing the apocalypse probably won't be tripped 599 00:37:40,926 --> 00:37:45,631 by a rogue planet is only slightly reassuring. 600 00:37:45,664 --> 00:37:48,867 The ancients and modern scientists agree, 601 00:37:48,900 --> 00:37:50,736 there is no escape. 602 00:37:50,769 --> 00:37:55,073 Somehow, someday, the end is coming, 603 00:37:55,106 --> 00:37:58,410 and the final vision of Armageddon 604 00:37:58,444 --> 00:38:00,346 is the strangest of all. 605 00:38:06,051 --> 00:38:09,321 (narrator) We've seen Armageddon rain down on us 606 00:38:09,355 --> 00:38:14,426 by Nordic ice and Buddhist fire, 607 00:38:14,460 --> 00:38:16,728 Aztec darkness, 608 00:38:16,762 --> 00:38:20,599 killer meteorites of Biblical proportions, 609 00:38:20,632 --> 00:38:24,436 and deep space death beams, 610 00:38:24,470 --> 00:38:27,606 but maybe there's hope. 611 00:38:27,639 --> 00:38:31,477 What if the end...isn't? 612 00:38:34,546 --> 00:38:37,115 The biggest recycling project in the universe 613 00:38:37,148 --> 00:38:41,753 might be the universe itself, 614 00:38:41,787 --> 00:38:44,856 and according to Ancient Hindu philosophy, 615 00:38:44,890 --> 00:38:51,062 every Armageddon marks a new beginning. 616 00:38:51,096 --> 00:38:54,433 (Markley) Hindu belief for the end of the world involves cycles. 617 00:38:54,466 --> 00:38:57,369 The end of the world was also the beginning of the world, 618 00:38:57,403 --> 00:38:59,571 which in due course would live out its life span, 619 00:38:59,605 --> 00:39:02,408 and it too would end and once more be reborn, 620 00:39:02,441 --> 00:39:05,977 in constant cycles. 621 00:39:06,011 --> 00:39:11,483 (narrator) Could this view of Armageddon really come to pass? 622 00:39:11,517 --> 00:39:14,686 Not if dark energy continues to expand the universe 623 00:39:14,720 --> 00:39:19,458 eternally, extinguishing it in a Big Chill. 624 00:39:21,727 --> 00:39:26,131 But the mysteries of dark energy leave open the possibility 625 00:39:26,164 --> 00:39:31,036 that instead of a Big Chill, there will be a Big Crunch, 626 00:39:31,069 --> 00:39:36,742 a universe that reverses course and collapses back in on itself. 627 00:39:40,078 --> 00:39:42,648 (Filippenko) It's conceivable that the dark energy 628 00:39:42,681 --> 00:39:45,484 could change sign in the future. 629 00:39:45,517 --> 00:39:48,019 Right now, it's repulsive, but what if someday, 630 00:39:48,053 --> 00:39:50,589 it becomes gravitationally attractive? 631 00:39:50,622 --> 00:39:52,491 We don't know what dark energy is, 632 00:39:52,524 --> 00:39:55,661 so it's possible. 633 00:39:55,694 --> 00:39:57,496 (narrator) During the big crunch, 634 00:39:57,529 --> 00:39:59,865 the universe would collapse... 635 00:39:59,898 --> 00:40:04,035 and collapse... and collapse... 636 00:40:04,069 --> 00:40:08,907 (Filippenko) Everything becomes so dense, so compressed, 637 00:40:08,940 --> 00:40:13,979 that we call this a singularity, a big crunch, 638 00:40:14,012 --> 00:40:18,617 a "gnab gib," which is "Big Bang" backwards. 639 00:40:18,650 --> 00:40:22,521 It's conceivable that there will be a rebirth, 640 00:40:22,554 --> 00:40:26,124 a new expansion, a new big bang, if you will. 641 00:40:29,060 --> 00:40:33,965 (narrator) Scientists call that the Big Bounce. 642 00:40:33,999 --> 00:40:35,567 It's very much like what happens 643 00:40:35,601 --> 00:40:40,038 if you take a ball and throw it up into the air. 644 00:40:40,071 --> 00:40:43,475 You give it that initial push, that would be like the Big Bang, 645 00:40:43,509 --> 00:40:46,144 it expands out, it goes up into the air, 646 00:40:46,177 --> 00:40:49,014 and then the gravity of the Earth eventually 647 00:40:49,047 --> 00:40:53,184 turns it round and brings it back down to your hand. 648 00:40:53,218 --> 00:40:55,120 (narrator) Toss it up again... 649 00:40:55,153 --> 00:40:58,990 and again... and that's the Big Bounce. 650 00:40:59,024 --> 00:41:02,060 (Howell) That's what's called the cyclic model in cosmology. 651 00:41:02,093 --> 00:41:06,264 The universe is born, dies, and then is reborn again, 652 00:41:06,297 --> 00:41:09,167 and this process could go over and over. 653 00:41:09,200 --> 00:41:12,203 It's akin to Hindu mythology. 654 00:41:14,773 --> 00:41:19,645 (narrator) If the universe does in fact crunch and bounce back, 655 00:41:19,678 --> 00:41:22,013 as the Ancient Hindus believed, 656 00:41:22,047 --> 00:41:24,082 then we might have been down this road 657 00:41:24,115 --> 00:41:27,285 many times before. 658 00:41:27,318 --> 00:41:32,624 Or maybe there isn't just one universe after all. 659 00:41:32,658 --> 00:41:36,562 We now think that there may well be other universes 660 00:41:36,595 --> 00:41:40,098 popping into existence with their own big bangs 661 00:41:40,131 --> 00:41:43,168 and their own expansion and their own stars 662 00:41:43,201 --> 00:41:46,237 and perhaps even their own life, 663 00:41:46,271 --> 00:41:51,176 and that process can lead to a progression of universes 664 00:41:51,209 --> 00:41:54,680 that is never-ending. 665 00:41:54,713 --> 00:42:01,286 (narrator) That's good news for universes, if not necessarily for us. 666 00:42:01,319 --> 00:42:05,757 If the Earth can dodge asteroid strikes 667 00:42:05,791 --> 00:42:10,762 and gamma ray bursts and rogue planet invasions, 668 00:42:10,796 --> 00:42:13,198 we can expect our sun to expand 669 00:42:13,231 --> 00:42:17,002 before burning out 5 billion years from now, 670 00:42:17,035 --> 00:42:21,707 incinerating the planet as the Buddhists envision. 671 00:42:21,740 --> 00:42:23,809 If dark energy can be trusted, 672 00:42:23,842 --> 00:42:26,344 the universe will continue to expand, 673 00:42:26,377 --> 00:42:28,313 freezing to death in the process, 674 00:42:28,346 --> 00:42:30,782 as the Norse predicted. 675 00:42:30,816 --> 00:42:34,052 Or maybe another universe will spring to life 676 00:42:34,085 --> 00:42:38,724 from the corpse of the old one, as some Hindus suggest. 677 00:42:38,757 --> 00:42:40,325 Whether we look to the ancient lore 678 00:42:40,358 --> 00:42:43,261 of the Aztecs, the Norse, 679 00:42:43,294 --> 00:42:47,966 the Hindus, the Buddhists, the Romans, 680 00:42:47,999 --> 00:42:53,238 or to modern science, the answer is the same-- 681 00:42:53,271 --> 00:42:55,974 We are doomed. 682 00:42:56,007 --> 00:42:58,209 (Markley) Sooner or later, things fail. 683 00:42:58,243 --> 00:43:00,779 Sooner or later, people die. 684 00:43:00,812 --> 00:43:03,849 Sooner or later, the world ends.