1 00:00:02,068 --> 00:00:04,059 The universe is home to real monsters. 2 00:00:04,137 --> 00:00:07,129 We can't see them, but we know they're out there. 3 00:00:07,207 --> 00:00:11,337 You really can't get anything bigger or stronger or scarier 4 00:00:11,411 --> 00:00:12,742 than a black hole. 5 00:00:12,812 --> 00:00:17,044 Black holes consume planets and stars... 6 00:00:17,117 --> 00:00:20,109 anything that gets too close. 7 00:00:20,186 --> 00:00:22,381 Black holes give physicists no end of headaches, 8 00:00:22,455 --> 00:00:24,252 'cause they break all the rules. 9 00:00:24,324 --> 00:00:29,421 But they rule the universe. 10 00:00:29,496 --> 00:00:30,861 They are center-stage. 11 00:00:32,465 --> 00:00:34,228 We now know they dominate 12 00:00:34,300 --> 00:00:37,428 the evolution of the universe itself. 13 00:00:58,525 --> 00:01:01,255 Black holes are the most mysterious objects 14 00:01:01,327 --> 00:01:02,988 in our universe. 15 00:01:03,063 --> 00:01:06,396 Their gravity is absolute. 16 00:01:08,601 --> 00:01:12,401 Nothing can escape. 17 00:01:12,472 --> 00:01:17,000 They can suck in whole galaxies. 18 00:01:17,077 --> 00:01:20,274 Black holes used to be science fiction. 19 00:01:20,346 --> 00:01:22,814 Now we know they're real. 20 00:01:22,882 --> 00:01:24,372 When I was a PhD student, 21 00:01:24,451 --> 00:01:27,818 people used to giggle when you'd hear about black holes. 22 00:01:27,887 --> 00:01:30,481 They're like unicorns, mythical creatures. 23 00:01:30,557 --> 00:01:32,252 We called this the "giggle factor." 24 00:01:32,325 --> 00:01:34,190 People would say, "Beam me up, Scotty." 25 00:01:34,260 --> 00:01:37,127 Well, no one is laughing anymore. 26 00:01:38,431 --> 00:01:40,763 So, they're not science fiction. 27 00:01:40,834 --> 00:01:42,893 Even though we've never landed in one, 28 00:01:42,969 --> 00:01:45,369 we have enough evidence to know that they're really out there. 29 00:01:51,311 --> 00:01:54,508 This image might not look like much to you and me, 30 00:01:54,581 --> 00:01:59,245 but to a scientist, it's proof that black holes exist. 31 00:01:59,319 --> 00:02:03,813 It's an actual movie of a black hole devouring a star 32 00:02:03,890 --> 00:02:06,450 in the constellation of Aquila. 33 00:02:06,526 --> 00:02:08,619 Black holes are messy eaters. 34 00:02:08,695 --> 00:02:10,993 The red spots you see are gas 35 00:02:11,064 --> 00:02:15,501 that's being spit out of the hole, into space. 36 00:02:15,568 --> 00:02:18,594 Eventually, over the next million years, 37 00:02:18,671 --> 00:02:23,472 this star will be eaten alive and disappear. 38 00:02:31,718 --> 00:02:34,050 A black hole is pretty much the end point of everything. 39 00:02:34,120 --> 00:02:36,554 It's the end point of a star. It's the end point of matter. 40 00:02:36,623 --> 00:02:39,148 It's the end point of energy. It's the end point of gravity. 41 00:02:39,225 --> 00:02:43,821 I mean, that's really it. That's the top of the scale. 42 00:02:48,468 --> 00:02:50,834 Although they have the power to destroy 43 00:02:50,904 --> 00:02:52,633 like nothing else in the universe, 44 00:02:52,705 --> 00:02:56,698 black holes also help build galaxies... 45 00:02:56,776 --> 00:03:00,712 a vital part of the great cosmic machine. 46 00:03:00,780 --> 00:03:02,714 Some astronomers think 47 00:03:02,782 --> 00:03:06,650 they could even be gateways to parallel universes. 48 00:03:11,858 --> 00:03:14,850 We are now entering the golden age of research 49 00:03:14,928 --> 00:03:16,327 in black-hole physics. 50 00:03:16,396 --> 00:03:18,990 They could be the key 51 00:03:19,065 --> 00:03:21,829 to understanding the birth of the universe, 52 00:03:21,901 --> 00:03:24,165 its formation, and then its death. 53 00:03:29,108 --> 00:03:31,076 Black holes really represent, 54 00:03:31,144 --> 00:03:33,374 in one sense, the frontier of modern astronomy. 55 00:03:33,446 --> 00:03:36,108 And they're changing our ideas about how galaxies form 56 00:03:36,182 --> 00:03:38,047 and, indeed, how the universe works. 57 00:03:38,117 --> 00:03:40,915 Their power comes 58 00:03:40,987 --> 00:03:44,718 from one of the primary forces in nature... gravity. 59 00:03:47,527 --> 00:03:49,757 I teach astronomy. 60 00:03:49,829 --> 00:03:51,319 And we teach our students 61 00:03:51,397 --> 00:03:55,163 that the fundamental principle of gravity is, "gravity sucks." 62 00:03:55,235 --> 00:03:58,727 Gravity keeps our feet on the ground 63 00:03:58,805 --> 00:04:01,831 and our planet orbiting around the Sun. 64 00:04:04,210 --> 00:04:09,705 But in a black hole, the force of gravity is off the charts... 65 00:04:09,782 --> 00:04:13,445 so strong, it sucks in anything nearby. 66 00:04:13,519 --> 00:04:18,980 It can even bend the light from distant stars. 67 00:04:19,058 --> 00:04:21,993 And if that light gets too close, 68 00:04:22,061 --> 00:04:24,461 the black hole swallows it. 69 00:04:24,530 --> 00:04:26,191 Think of it like this. 70 00:04:26,266 --> 00:04:29,064 Imagine a black hole as a waterfall. 71 00:04:29,135 --> 00:04:32,468 Gravity is the river flowing toward the falls, 72 00:04:32,538 --> 00:04:34,870 and a beam of light... the kayak. 73 00:04:34,941 --> 00:04:38,104 Upriver from the waterfall, the current is weak. 74 00:04:38,177 --> 00:04:41,669 The kayaker can paddle against it and get away. 75 00:04:41,748 --> 00:04:45,184 But closer to the waterfall, the current is stronger, 76 00:04:45,251 --> 00:04:50,154 and the kayaker struggles to escape. 77 00:04:50,223 --> 00:04:56,093 The edge of the waterfall is like the edge of a black hole. 78 00:04:56,162 --> 00:05:00,997 No matter how strong the kayaker is, he's going down. 79 00:05:01,067 --> 00:05:02,728 It's the same in space. 80 00:05:02,802 --> 00:05:05,896 The way black holes are really devastating 81 00:05:05,972 --> 00:05:08,236 is because when you get close to them, 82 00:05:08,308 --> 00:05:09,969 the gravity gets super-strong. 83 00:05:15,381 --> 00:05:18,316 So strong that they eat light. 84 00:05:18,384 --> 00:05:21,319 That's why black holes are black. 85 00:05:26,693 --> 00:05:29,184 A black hole is like a roach motel. 86 00:05:29,262 --> 00:05:32,163 Everything checks in. Nothing checks out. 87 00:05:36,402 --> 00:05:39,428 Anything that gets too close is doomed... 88 00:05:39,505 --> 00:05:45,137 planets, stars, even whole solar systems. 89 00:05:51,984 --> 00:05:55,420 And don't think this is some faraway phenomenon. 90 00:05:55,488 --> 00:05:57,752 Black holes are on the loose 91 00:05:57,824 --> 00:06:01,590 right here in our own cosmic neighborhood. 92 00:06:01,661 --> 00:06:04,061 We now know there are wandering nomads 93 00:06:04,130 --> 00:06:06,291 throughout the Milky Way galaxy... 94 00:06:06,366 --> 00:06:09,392 vagabonds throughout the galaxy, 95 00:06:09,469 --> 00:06:12,597 where black holes can come up right behind you 96 00:06:12,672 --> 00:06:15,368 and perhaps gobble you up, and they won't even burp. 97 00:06:15,441 --> 00:06:19,172 If one ever comes close, watch out. 98 00:06:19,245 --> 00:06:23,682 If a black hole found its way into our solar system, 99 00:06:23,750 --> 00:06:25,411 it would rip us apart. 100 00:06:25,485 --> 00:06:27,385 Any kind of black hole 101 00:06:27,453 --> 00:06:29,717 that could pass through the solar system 102 00:06:29,789 --> 00:06:31,450 would be pulling on all the planets 103 00:06:31,524 --> 00:06:32,650 harder than the Sun does. 104 00:06:32,725 --> 00:06:34,522 And so it's just gonna totally disrupt 105 00:06:34,594 --> 00:06:36,755 the gravitational balance of the solar system. 106 00:06:36,829 --> 00:06:42,233 The black hole would literally tear planets from their orbits 107 00:06:42,301 --> 00:06:44,428 and smash them into each other. 108 00:06:51,811 --> 00:06:55,838 It's just an epic disaster. It's a bull in a china shop. 109 00:07:00,219 --> 00:07:02,585 If it got close enough to, say, Jupiter, 110 00:07:02,655 --> 00:07:04,850 it could actually pull the moons of Jupiter 111 00:07:04,924 --> 00:07:06,084 away from the planet itself. 112 00:07:09,228 --> 00:07:11,492 It would just be flinging planets left and right 113 00:07:11,564 --> 00:07:13,828 everywhere as it whipped through the solar system, 114 00:07:13,900 --> 00:07:16,232 leaving disaster in its wake. 115 00:07:21,040 --> 00:07:24,009 If a black hole approached Earth, 116 00:07:24,076 --> 00:07:27,705 all that gravity would rip asteroids from their orbits 117 00:07:27,780 --> 00:07:29,873 and hurl them toward our planet. 118 00:07:38,591 --> 00:07:41,492 The Earth's surface would become an inferno. 119 00:07:41,561 --> 00:07:45,258 It would be the beginning of the end. 120 00:07:49,936 --> 00:07:52,530 First, it would swallow up the atmosphere, 121 00:07:52,605 --> 00:07:55,096 then the planet itself. 122 00:08:00,480 --> 00:08:03,381 Destroying an entire solar system 123 00:08:03,449 --> 00:08:05,815 is nothing to a black hole. 124 00:08:05,885 --> 00:08:10,788 But it's more than just a big, empty, sucking piece of space. 125 00:08:10,857 --> 00:08:13,690 It's incredibly heavy. 126 00:08:13,759 --> 00:08:18,162 To get an idea just how heavy and dense a black hole is, 127 00:08:18,231 --> 00:08:19,858 imagine the Earth. 128 00:08:19,932 --> 00:08:23,197 Now start to crush it... 129 00:08:25,872 --> 00:08:29,239 ...and keep crushing until it's packed so tight 130 00:08:29,308 --> 00:08:32,402 even the atoms themselves collapse. 131 00:08:35,314 --> 00:08:39,546 When the Earth crushes down to just 2 inches across, 132 00:08:39,619 --> 00:08:42,520 that's the density of a black hole. 133 00:08:42,588 --> 00:08:45,318 It would be the size of a golf ball, 134 00:08:45,391 --> 00:08:51,193 yet weigh the same as the Earth, with the same amount of gravity. 135 00:08:51,264 --> 00:08:55,064 What can make something that small, 136 00:08:55,134 --> 00:08:58,934 that dense, and that powerful? 137 00:08:59,005 --> 00:09:03,135 We don't have external forces, large pistons in the universe, 138 00:09:03,209 --> 00:09:04,733 to create black holes. 139 00:09:04,810 --> 00:09:07,506 So the only way the real black holes of the universe form 140 00:09:07,580 --> 00:09:09,548 is if gravity can do the job itself. 141 00:09:09,615 --> 00:09:13,415 There is only one place in the universe 142 00:09:13,486 --> 00:09:16,216 that generates that much gravity. 143 00:09:16,289 --> 00:09:19,019 And it's inside the largest stars. 144 00:09:19,091 --> 00:09:24,358 When massive stars 10 times heavier than our sun die, 145 00:09:24,430 --> 00:09:26,398 gravity crushes them, 146 00:09:26,465 --> 00:09:29,992 creating a huge explosion, a supernova. 147 00:09:40,279 --> 00:09:45,615 But some stars are even bigger than that. 148 00:09:45,685 --> 00:09:50,645 These supermassive stars weigh 100 times more than our sun 149 00:09:50,723 --> 00:09:53,521 and have 100 times more gravity. 150 00:09:53,593 --> 00:09:55,925 When one of these stars dies, 151 00:09:55,995 --> 00:10:01,661 it sets off the biggest explosion in the universe... 152 00:10:01,734 --> 00:10:03,861 A hypernova. 153 00:10:13,746 --> 00:10:18,080 This is the birth of a black hole. 154 00:10:24,557 --> 00:10:29,426 Our universe is full of stars. 155 00:10:29,495 --> 00:10:33,363 At the end of their lives, some die quietly. 156 00:10:33,432 --> 00:10:37,664 Others go out in spectacular explosions. 157 00:10:37,737 --> 00:10:43,141 And some give birth to black holes. 158 00:10:43,209 --> 00:10:45,074 If you have a star, 159 00:10:45,144 --> 00:10:48,375 a supermassive star that's 100 times the mass of the Sun, 160 00:10:48,447 --> 00:10:51,348 at the end of its life, the core runs out of fuel. 161 00:10:51,417 --> 00:10:53,248 There's nothing left to hold it up, 162 00:10:53,319 --> 00:10:55,787 and the core collapses down into a black hole. 163 00:10:55,855 --> 00:10:59,518 When that happens, the enormous gravity 164 00:10:59,592 --> 00:11:04,586 generated at the heart of supermassive stars runs wild. 165 00:11:07,533 --> 00:11:12,402 This is the dying star V.Y. Canis Majoris. 166 00:11:12,471 --> 00:11:16,999 It's more than a billion miles across. 167 00:11:20,246 --> 00:11:24,615 Like all stars, it's a giant nuclear-fusion reactor, 168 00:11:24,684 --> 00:11:27,016 pumping energy outward. 169 00:11:27,086 --> 00:11:32,524 At the same time, the star's extreme gravity crushes inward. 170 00:11:32,591 --> 00:11:34,559 For a few million years, 171 00:11:34,627 --> 00:11:38,654 fusion and gravity are locked in standoff. 172 00:11:38,731 --> 00:11:41,723 But when the star runs out of fuel, 173 00:11:41,801 --> 00:11:45,635 fusion stops and the stalemate ends. 174 00:11:45,705 --> 00:11:47,434 Gravity wins. 175 00:11:50,476 --> 00:11:52,068 In a millisecond, 176 00:11:52,144 --> 00:11:55,409 the core shrinks to a fraction of its original size 177 00:11:55,481 --> 00:11:59,542 and a baby black hole is born. 178 00:11:59,618 --> 00:12:01,142 Immediately, 179 00:12:01,220 --> 00:12:05,054 it starts to cannibalize what's left of the star. 180 00:12:05,124 --> 00:12:08,491 As matter swirls into the black hole, it gets incredibly hot. 181 00:12:08,561 --> 00:12:11,029 And there are magnetic forces and frictional forces, 182 00:12:11,097 --> 00:12:13,122 and it's just a witch's brew, a nightmare, 183 00:12:13,199 --> 00:12:15,895 what's going on right above the surface of the black hole. 184 00:12:15,968 --> 00:12:18,562 The new black hole in the middle 185 00:12:18,637 --> 00:12:21,538 keeps feeding on the body of the star around it. 186 00:12:21,607 --> 00:12:26,306 It eats the gas so fast, it chokes and coughs, 187 00:12:26,378 --> 00:12:29,541 blasting out huge beams of energy. 188 00:12:33,719 --> 00:12:36,847 They basically eat their way out from the star. 189 00:12:36,922 --> 00:12:38,685 This happens in milliseconds. 190 00:12:38,758 --> 00:12:41,522 It happens before the rest of the star even knows 191 00:12:41,594 --> 00:12:43,027 the core is gone. 192 00:12:43,095 --> 00:12:47,532 And so basically, the star is dead before it hits the ground. 193 00:12:51,203 --> 00:12:55,003 Finally, the star explodes. 194 00:12:57,743 --> 00:13:02,942 In one second, it blasts out 100 times more energy 195 00:13:03,015 --> 00:13:07,213 than our sun will produce over its entire life. 196 00:13:09,688 --> 00:13:14,421 What's left is a new black hole and two jets of energy 197 00:13:14,493 --> 00:13:19,089 hurtling through the universe at the speed of light. 198 00:13:19,165 --> 00:13:22,794 These jets are called "gamma-ray bursts." 199 00:13:28,240 --> 00:13:31,300 They're incredibly energetic events. 200 00:13:31,377 --> 00:13:33,641 In terms of raw energy and power, 201 00:13:33,712 --> 00:13:36,943 gamma ray bursts are second only to the Big Bang itself. 202 00:13:38,584 --> 00:13:41,519 Most of them last only a few seconds. 203 00:13:41,587 --> 00:13:45,023 And they fry anything in their way. 204 00:13:48,928 --> 00:13:52,227 They're so intense that if there was a gamma-ray burster 205 00:13:52,298 --> 00:13:55,267 in the region of our galaxy near our solar system, 206 00:13:55,334 --> 00:13:58,667 it could literally vaporize the entire planet. 207 00:13:58,737 --> 00:14:03,765 Fortunately, most gamma-ray bursts occur outside our galaxy. 208 00:14:10,783 --> 00:14:13,684 But they tell us something important 209 00:14:13,752 --> 00:14:18,712 about black holes and how our universe works. 210 00:14:18,791 --> 00:14:22,090 What we were seeing every time a gamma-ray burst went off 211 00:14:22,161 --> 00:14:24,789 was basically the birth cry of a black hole. 212 00:14:24,864 --> 00:14:29,995 By counting gamma-ray bursts, astronomers can figure out 213 00:14:30,069 --> 00:14:32,697 how many black holes are being created. 214 00:14:32,771 --> 00:14:36,969 In 2004, NASA launched the Swift probe 215 00:14:37,042 --> 00:14:40,443 to scan the universe for gamma-ray bursts. 216 00:14:40,512 --> 00:14:41,444 Five... 217 00:14:41,513 --> 00:14:42,480 four... 218 00:14:42,548 --> 00:14:43,515 three... 219 00:14:43,582 --> 00:14:44,640 two... 220 00:14:44,717 --> 00:14:46,776 one... We have ignition. 221 00:14:46,852 --> 00:14:50,185 And we have lift-off of NASA's Swift spacecraft, 222 00:14:50,256 --> 00:14:53,487 on a mission to study and understand gamma-ray bursts 223 00:14:53,559 --> 00:14:55,026 throughout the universe. 224 00:15:01,433 --> 00:15:04,459 This is the most powerful gamma-ray burst 225 00:15:04,536 --> 00:15:06,629 Swift has detected so far. 226 00:15:06,705 --> 00:15:10,607 The flash of light announces the birth of a new black hole 227 00:15:10,676 --> 00:15:13,144 on the other side of the universe. 228 00:15:17,416 --> 00:15:22,183 Swift can only look at a fraction of what's out there. 229 00:15:26,525 --> 00:15:31,326 Still, it detects at least one gamma-ray burst every day. 230 00:15:33,299 --> 00:15:37,895 That discovery rocked astronomy to its foundations. 231 00:15:40,339 --> 00:15:43,103 We once thought that black holes, like unicorns, 232 00:15:43,175 --> 00:15:45,735 could never be found. 233 00:15:45,811 --> 00:15:49,144 We now believe that there are perhaps billions of black holes 234 00:15:49,214 --> 00:15:50,442 in the night sky. 235 00:15:50,516 --> 00:15:53,144 When we look around our galaxy and other galaxies, 236 00:15:53,218 --> 00:15:58,019 it's clear that the universe is full of powerful black holes. 237 00:15:58,090 --> 00:16:00,581 Finding black holes is one thing. 238 00:16:00,659 --> 00:16:02,251 Figuring out how they work... 239 00:16:02,328 --> 00:16:04,421 that's a whole different ball game. 240 00:16:04,496 --> 00:16:07,192 The only way to find out is to visit one. 241 00:16:07,266 --> 00:16:11,600 You'd have to take a spacecraft across the vastness of space 242 00:16:11,670 --> 00:16:13,433 just to get close to it. 243 00:16:13,505 --> 00:16:17,669 Then you'd have to go inside the black hole. 244 00:16:17,743 --> 00:16:19,574 There, you'd find a place 245 00:16:19,645 --> 00:16:23,775 where reality breaks down and time stands still. 246 00:16:27,453 --> 00:16:30,752 There are billions of black holes in the universe. 247 00:16:30,823 --> 00:16:34,122 We can detect them with telescopes and satellites. 248 00:16:34,193 --> 00:16:38,789 But we don't actually know what they're like up-close. 249 00:16:38,864 --> 00:16:40,195 It's a long way off, 250 00:16:40,265 --> 00:16:42,825 but scientists are already speculating 251 00:16:42,901 --> 00:16:46,200 about a mission to a black hole... 252 00:16:46,271 --> 00:16:51,004 A one-way trip to the most dangerous place in the universe. 253 00:16:54,747 --> 00:16:56,180 Originally, 254 00:16:56,248 --> 00:17:01,083 physicists were horrified at the idea of black holes. 255 00:17:01,153 --> 00:17:02,677 They wanted to banish them, 256 00:17:02,755 --> 00:17:05,417 because the laws of physics, as we know them, 257 00:17:05,491 --> 00:17:08,392 seem to break down at the instant of a black hole. 258 00:17:08,460 --> 00:17:10,018 Time stops. 259 00:17:11,463 --> 00:17:14,227 Gravity becomes infinite. 260 00:17:14,299 --> 00:17:17,666 This is a nightmare. 261 00:17:17,736 --> 00:17:21,035 Obviously, we can't send humans anywhere near a black hole. 262 00:17:21,106 --> 00:17:23,768 But a robot? Well, sure. 263 00:17:23,842 --> 00:17:26,902 A robotic probe could transmit data back 264 00:17:26,979 --> 00:17:29,641 just before it goes over the edge. 265 00:17:29,715 --> 00:17:34,652 That edge of a black hole is called the "event horizon." 266 00:17:34,720 --> 00:17:36,847 It's the edge of time and space... 267 00:17:36,922 --> 00:17:40,483 at least, in the universe we know. 268 00:17:40,559 --> 00:17:42,550 We call the event horizon "event horizon" 269 00:17:42,628 --> 00:17:43,617 quite simply because 270 00:17:43,695 --> 00:17:45,458 it separates space into two regions. 271 00:17:48,267 --> 00:17:49,666 It's not a physical surface. 272 00:17:49,735 --> 00:17:53,034 You might not even notice it if you were falling through it, 273 00:17:53,105 --> 00:17:56,302 but ultimately, once you're inside of it, you're doomed. 274 00:17:56,375 --> 00:17:58,502 As you approach the event horizon, 275 00:17:58,577 --> 00:18:00,272 gravity gets stronger 276 00:18:00,345 --> 00:18:04,372 and very strange things start to happen. 277 00:18:04,450 --> 00:18:07,578 As you fall into a black hole feet-first, 278 00:18:07,653 --> 00:18:10,121 your feet are closer to the black hole. 279 00:18:10,189 --> 00:18:13,818 And so the gravity they feel is stronger. 280 00:18:13,892 --> 00:18:15,621 Your head is not quite as close, 281 00:18:15,694 --> 00:18:17,821 and so the gravity it feels is less. 282 00:18:17,896 --> 00:18:20,592 And basically, what happens is, you get stretched out. 283 00:18:20,666 --> 00:18:22,964 Your feet are being pulled much harder than your head, 284 00:18:23,035 --> 00:18:24,332 and you're like a piece of taffy 285 00:18:24,403 --> 00:18:26,132 being pulled between two strong people. 286 00:18:28,607 --> 00:18:30,666 As you get thinner and thinner and thinner, 287 00:18:30,742 --> 00:18:32,710 as you get closer and closer and closer, 288 00:18:32,778 --> 00:18:36,270 you're undergoing a process we call "spaghettification" 289 00:18:36,348 --> 00:18:40,307 because you're basically turned into a long, thin tube of pasta. 290 00:18:44,256 --> 00:18:47,714 Gravity would stretch our robotic probe to the limit, 291 00:18:47,793 --> 00:18:49,488 then rip it apart. 292 00:18:58,137 --> 00:19:00,571 But imagine if the probe was strong enough 293 00:19:00,639 --> 00:19:03,073 to survive and keep going. 294 00:19:06,011 --> 00:19:11,381 As it gets close to the event horizon, everything goes crazy. 295 00:19:11,450 --> 00:19:16,945 Gravity is so extreme, it stops time. 296 00:19:17,022 --> 00:19:19,286 We think of time as being endless. 297 00:19:19,358 --> 00:19:22,521 However, in a black hole, in some sense, time stops. 298 00:19:26,798 --> 00:19:29,767 This sounds like it's nuts, but that's the way it works. 299 00:19:29,835 --> 00:19:31,200 It's in the math. 300 00:19:31,270 --> 00:19:35,604 It's actually woven into the fabric of the universe itself. 301 00:19:35,674 --> 00:19:38,370 If you were to watch from a distance, 302 00:19:38,443 --> 00:19:40,775 the robot probe would seem to slow down 303 00:19:40,846 --> 00:19:43,314 as it gets closer to the black hole. 304 00:19:43,382 --> 00:19:47,113 Then it would appear to stop completely. 305 00:19:47,186 --> 00:19:50,246 The whole process might just take a brief moment. 306 00:19:50,322 --> 00:19:51,653 But from the outside, 307 00:19:51,723 --> 00:19:55,853 you appear to freeze and fall ever more slowly. 308 00:19:55,928 --> 00:19:58,556 You actually can never observe an object fall 309 00:19:58,630 --> 00:20:00,928 all the way through the event horizon. 310 00:20:00,999 --> 00:20:03,365 It literally freezes at the surface 311 00:20:03,435 --> 00:20:06,529 because its clock is going infinitely slowly 312 00:20:06,605 --> 00:20:08,038 compared to yours. 313 00:20:08,106 --> 00:20:12,941 In reality, the probe hasn't stopped at all. 314 00:20:13,011 --> 00:20:17,209 It keeps going and crosses the event horizon. 315 00:20:19,117 --> 00:20:22,018 If the probe points its cameras backwards, 316 00:20:22,087 --> 00:20:24,487 towards the entrance of the black hole, 317 00:20:24,556 --> 00:20:30,153 it will see light being sucked in. 318 00:20:30,229 --> 00:20:35,223 If it points the camera forward, at first it sees only black, 319 00:20:35,300 --> 00:20:38,633 but as it moves toward the heart of the black hole, 320 00:20:38,704 --> 00:20:43,471 it encounters the most bizarre place in the universe. 321 00:20:45,110 --> 00:20:49,046 The black hole's immense gravity pulls everything down 322 00:20:49,114 --> 00:20:52,447 to an unimaginably small point at its center. 323 00:20:52,517 --> 00:20:57,045 Scientists call it the "singularity." 324 00:20:57,122 --> 00:20:59,613 We really just don't know 325 00:20:59,691 --> 00:21:01,818 what happens at the center of a black hole. 326 00:21:01,893 --> 00:21:03,121 The densities are so great 327 00:21:03,195 --> 00:21:05,720 that the laws of physics break down, as we know them. 328 00:21:05,797 --> 00:21:10,496 A singularity is a point of infinite gravity, 329 00:21:10,569 --> 00:21:13,697 where space and time become meaningless. 330 00:21:13,772 --> 00:21:15,603 Now, that is ridiculous. 331 00:21:15,674 --> 00:21:20,475 A singularity is basically a word for saying "I don't know." 332 00:21:20,545 --> 00:21:22,809 It's a word for saying "I'm clueless." 333 00:21:27,085 --> 00:21:28,211 Even now, 334 00:21:28,287 --> 00:21:30,778 scientists can't really answer the question, 335 00:21:30,856 --> 00:21:32,153 "What is a black hole?" 336 00:21:32,224 --> 00:21:33,748 It's upsetting, a little bit, 337 00:21:33,825 --> 00:21:35,349 to think that there are objects out there 338 00:21:35,427 --> 00:21:37,759 that are breaking the laws of physics. 339 00:21:37,829 --> 00:21:40,161 There must be bigger laws 340 00:21:40,232 --> 00:21:42,063 that are being used by these black holes, 341 00:21:42,134 --> 00:21:43,999 that are being obeyed by these black holes, 342 00:21:44,069 --> 00:21:45,627 that we just don't understand yet. 343 00:21:49,141 --> 00:21:52,235 Okay, so, the one thing we do understand 344 00:21:52,311 --> 00:21:55,747 is that black holes are born from dying stars. 345 00:21:57,883 --> 00:22:01,341 And most are small... around 20 miles across. 346 00:22:04,690 --> 00:22:07,659 But now scientists have discovered 347 00:22:07,726 --> 00:22:10,957 that some black holes are much bigger. 348 00:22:11,029 --> 00:22:14,157 They're called "supermassive black holes." 349 00:22:14,232 --> 00:22:18,498 They're the same size as our entire solar system. 350 00:22:18,570 --> 00:22:24,065 And one of these monsters lies at the heart of our own galaxy. 351 00:22:28,613 --> 00:22:32,982 Our solar system lies in the Milky Way galaxy. 352 00:22:33,051 --> 00:22:37,647 It's made up of billions of stars, including our sun... 353 00:22:39,958 --> 00:22:43,018 ...all revolving around a mysterious region 354 00:22:43,095 --> 00:22:45,689 right at the center. 355 00:22:45,764 --> 00:22:48,995 Children ask the question... 356 00:22:49,067 --> 00:22:50,694 if the Moon goes around the Earth, 357 00:22:50,769 --> 00:22:52,066 the Earth goes around the Sun, 358 00:22:52,137 --> 00:22:53,798 then what does the Sun go around? 359 00:22:53,872 --> 00:22:55,271 It's a good question. 360 00:22:55,340 --> 00:22:57,638 And astronomers ask the same thing. 361 00:22:57,709 --> 00:22:59,734 Maybe there was something going on 362 00:22:59,811 --> 00:23:01,506 at the heart of the Milky Way... 363 00:23:01,580 --> 00:23:06,950 perhaps a black hole at the very center. 364 00:23:07,018 --> 00:23:11,079 But because we can't actually see a black hole, 365 00:23:11,156 --> 00:23:16,253 the best they could do was look for telltale signs. 366 00:23:16,328 --> 00:23:17,989 Using infrared telescopes, 367 00:23:18,063 --> 00:23:20,691 they looked at the middle of the galaxy 368 00:23:20,766 --> 00:23:24,065 and discovered a densely packed swarm 369 00:23:24,136 --> 00:23:25,967 of millions of stars. 370 00:23:26,037 --> 00:23:29,905 But they couldn't see what was at the center. 371 00:23:35,080 --> 00:23:39,574 One team has spent 15 years looking for clues. 372 00:23:44,256 --> 00:23:47,487 High above the clouds on Mauna Kea, in Hawaii, 373 00:23:47,559 --> 00:23:50,858 the giant Keck telescope has the power 374 00:23:50,929 --> 00:23:55,366 to see right through to the center of the Milky Way. 375 00:24:02,140 --> 00:24:04,768 The region which we have to study 376 00:24:04,843 --> 00:24:08,142 to prove that there's a black hole is incredibly small. 377 00:24:08,213 --> 00:24:09,805 It is absolutely the case 378 00:24:09,881 --> 00:24:12,406 of looking for a needle in a haystack, 379 00:24:12,484 --> 00:24:15,317 except we know exactly where the needle is. 380 00:24:17,189 --> 00:24:20,249 Andrea Ghez has spent countless nights 381 00:24:20,325 --> 00:24:22,589 scanning the center of the galaxy 382 00:24:22,661 --> 00:24:24,993 for signs of a black hole. 383 00:24:25,063 --> 00:24:26,860 To be able to do this experiment, 384 00:24:26,932 --> 00:24:28,297 one has to be able to see 385 00:24:28,366 --> 00:24:31,130 the stars that are very close to the center of the galaxy 386 00:24:31,203 --> 00:24:33,967 and to position them incredibly accurately. 387 00:24:34,039 --> 00:24:35,768 And this would be equivalent 388 00:24:35,841 --> 00:24:38,833 to me in Los Angeles looking at you in New York 389 00:24:38,910 --> 00:24:42,971 and seeing you be able to move your finger like this. 390 00:24:56,828 --> 00:24:58,693 As the Keck kicks into action, 391 00:24:58,763 --> 00:25:02,790 a laser beam detects tiny disturbances in the atmosphere 392 00:25:02,868 --> 00:25:05,234 that would distort the image. 393 00:25:07,973 --> 00:25:13,843 Motors then adjust the huge 30-foot mirror to compensate. 394 00:25:13,912 --> 00:25:16,073 The image is clear enough 395 00:25:16,147 --> 00:25:20,174 to track the stars at the heart of our galaxy. 396 00:25:22,521 --> 00:25:26,981 Ghez has taken thousands of images over the last 15 years. 397 00:25:27,058 --> 00:25:32,587 And what they reveal is amazing. 398 00:25:32,664 --> 00:25:35,326 The stars at the center of the galaxy 399 00:25:35,400 --> 00:25:38,267 are moving at millions of miles an hour. 400 00:25:44,743 --> 00:25:49,112 The center of the galaxy is a very extreme environment. 401 00:25:49,180 --> 00:25:51,080 The speeds with which stars move 402 00:25:51,149 --> 00:25:54,118 is much higher than anywhere else in our galaxy. 403 00:25:54,185 --> 00:25:56,949 And that is absolutely the signpost of the black hole. 404 00:26:02,294 --> 00:26:08,130 They look like tiny planets racing around an invisible sun. 405 00:26:08,199 --> 00:26:11,657 But they're not planets. They're stars. 406 00:26:11,736 --> 00:26:13,727 It takes a lot of gravity 407 00:26:13,805 --> 00:26:18,071 to swing huge stars around in such fast, tight orbits. 408 00:26:18,143 --> 00:26:23,103 There's only one thing in the universe with that much pull... 409 00:26:23,181 --> 00:26:28,175 a supermassive black hole. 410 00:26:28,253 --> 00:26:30,448 Watching these things shows the presence 411 00:26:30,522 --> 00:26:33,320 of a 4-million-times- the-mass-of-our-sun black hole, 412 00:26:33,391 --> 00:26:35,655 located right at the heart of our galaxy. 413 00:26:37,329 --> 00:26:39,490 It is a huge discovery. 414 00:26:39,564 --> 00:26:43,330 Everything in our galaxy, including our own solar system, 415 00:26:43,401 --> 00:26:48,065 orbits around a supermassive black hole. 416 00:26:48,139 --> 00:26:51,165 But the Milky Way isn't the only galaxy 417 00:26:51,242 --> 00:26:53,540 with a black hole in the middle. 418 00:26:53,612 --> 00:26:55,773 There are supermassive black holes 419 00:26:55,847 --> 00:26:59,248 at the heart of most galaxies in the universe. 420 00:26:59,317 --> 00:27:02,809 The Andromeda galaxy is our closest neighbor. 421 00:27:02,887 --> 00:27:06,323 It circles around a supermassive black hole 422 00:27:06,391 --> 00:27:11,090 weighing 140 million times more than our sun. 423 00:27:11,162 --> 00:27:14,529 Other galaxies, like this one, M87, 424 00:27:14,599 --> 00:27:20,538 have black holes weighing as much as 20 billion suns. 425 00:27:20,605 --> 00:27:23,165 How do black holes get so big, 426 00:27:23,241 --> 00:27:27,610 and what are they doing at the center of galaxies? 427 00:27:27,679 --> 00:27:33,083 For answers, we have to go back nearly 14 billion years 428 00:27:33,151 --> 00:27:37,087 to the beginning of the universe. 429 00:27:37,155 --> 00:27:38,816 Back then, 430 00:27:38,890 --> 00:27:43,452 the universe was filled with clouds of gas from the Big Bang. 431 00:27:43,528 --> 00:27:45,052 In some places, 432 00:27:45,130 --> 00:27:48,964 the gas was thick enough for millions of stars to form. 433 00:27:53,872 --> 00:27:57,035 Most of these new stars were supermassive. 434 00:27:57,108 --> 00:27:59,099 They burned hot and fast 435 00:27:59,177 --> 00:28:03,204 and then exploded, creating lots of black holes. 436 00:28:13,792 --> 00:28:16,556 The early universe was a wild-and-crazy place 437 00:28:16,628 --> 00:28:18,823 where huge regions of mass 438 00:28:18,897 --> 00:28:20,194 were collapsing catastrophically, 439 00:28:20,265 --> 00:28:21,527 producing black holes. 440 00:28:21,599 --> 00:28:24,295 And, in fact, the early universe might have been 441 00:28:24,369 --> 00:28:26,735 full of emerging black holes everywhere. 442 00:28:29,441 --> 00:28:32,137 Gravity pulled many of them together. 443 00:28:32,210 --> 00:28:34,474 All over the early universe, 444 00:28:34,546 --> 00:28:38,744 they merged, creating larger and larger black holes. 445 00:28:41,753 --> 00:28:45,484 Over hundreds of millions of years, each black hole grew, 446 00:28:45,557 --> 00:28:49,926 producing stronger gravity and pulling in more and more gas. 447 00:28:49,994 --> 00:28:54,590 New stars were born from the gas, forming primitive galaxies. 448 00:28:56,668 --> 00:29:00,468 But the black hole kept on sucking in gas, 449 00:29:00,538 --> 00:29:02,335 until it could take no more, 450 00:29:02,407 --> 00:29:06,468 igniting the most powerful flamethrower in the universe. 451 00:29:20,492 --> 00:29:23,859 A young galaxy is a vast cluster of stars, 452 00:29:23,928 --> 00:29:26,954 stars that formed from clouds of gas. 453 00:29:31,903 --> 00:29:34,371 At the center of the new galaxy 454 00:29:34,439 --> 00:29:38,842 is a young, supermassive black hole feeding on the gas, 455 00:29:38,910 --> 00:29:40,844 getting bigger and bigger. 456 00:29:40,912 --> 00:29:42,106 If you can imagine, 457 00:29:42,180 --> 00:29:45,047 when a galaxy is very young and still forming, 458 00:29:45,116 --> 00:29:47,880 there's a supermassive black hole forming at the core, 459 00:29:47,952 --> 00:29:49,886 and the gas is still falling into it 460 00:29:49,954 --> 00:29:51,421 and still forming the galaxy. 461 00:29:51,489 --> 00:29:53,787 Well, near that central black hole, 462 00:29:53,858 --> 00:29:55,485 things are getting very hot. 463 00:29:55,560 --> 00:29:57,187 That material is heating up. 464 00:29:57,262 --> 00:30:00,823 Gas is speeding into the black hole. 465 00:30:00,899 --> 00:30:03,333 But it overloads, 466 00:30:03,401 --> 00:30:08,065 and there is no room for all that excess hot gas. 467 00:30:08,139 --> 00:30:12,473 It has nowhere to go but out. 468 00:30:12,544 --> 00:30:17,607 It's blasted into space in huge jets of energy. 469 00:30:22,253 --> 00:30:25,711 Each jet is 20 times wider than our solar system 470 00:30:25,790 --> 00:30:29,954 and shoots clear through the galaxy. 471 00:30:30,028 --> 00:30:35,933 The supermassive black hole has ignited a quasar. 472 00:30:36,000 --> 00:30:37,695 Quasars are literally 473 00:30:37,769 --> 00:30:39,862 the brightest objects in the universe. 474 00:30:39,938 --> 00:30:42,930 They're so intense, they can outshine an entire galaxy. 475 00:30:43,007 --> 00:30:45,771 This is a real photograph 476 00:30:45,844 --> 00:30:49,644 of a real quasar in the galaxy M87, 477 00:30:49,714 --> 00:30:53,309 50 million light-years away. 478 00:30:56,788 --> 00:31:00,383 Quasars blast away huge quantities of gas 479 00:31:00,458 --> 00:31:02,392 from the surrounding galaxy... 480 00:31:05,096 --> 00:31:09,624 ...the equivalent of 10 Earths every minute. 481 00:31:13,071 --> 00:31:15,198 When you heat up a gas, 482 00:31:15,273 --> 00:31:17,366 it tends to expand and it blows outward. 483 00:31:17,442 --> 00:31:20,070 And it's sort of like a wind, but on a huge scale. 484 00:31:20,144 --> 00:31:22,112 And you get a black-hole wind, 485 00:31:22,180 --> 00:31:24,705 gas blowing out from the black hole. 486 00:31:24,782 --> 00:31:29,481 Black holes suck gas in. Quasars blow it out. 487 00:31:29,554 --> 00:31:34,116 But eventually there's no gas left to make stars, 488 00:31:34,192 --> 00:31:35,887 and the galaxy stops growing. 489 00:31:35,960 --> 00:31:38,690 So we think that the eventual size 490 00:31:38,763 --> 00:31:40,253 that a galaxy can achieve 491 00:31:40,331 --> 00:31:42,822 depends on the black hole in its center. 492 00:31:42,901 --> 00:31:44,425 The two are tied together. 493 00:31:46,404 --> 00:31:51,205 With no gas left to feed on, the quasar jets shrink and die. 494 00:31:52,677 --> 00:31:55,703 What's left is a supermassive black hole 495 00:31:55,780 --> 00:32:00,183 at the center of the galaxy, with a whole lot of young stars, 496 00:32:00,251 --> 00:32:04,187 just like our Milky Way back when it was young. 497 00:32:04,255 --> 00:32:06,917 Early on in the history of the Milky Way, 498 00:32:06,991 --> 00:32:10,324 when it was a young galaxy, we were probably a quasar. 499 00:32:10,395 --> 00:32:13,831 Probably every big galaxy was a quasar when it was young. 500 00:32:13,898 --> 00:32:15,388 But right now we're old enough 501 00:32:15,466 --> 00:32:17,434 that the galaxy has quieted down. 502 00:32:19,203 --> 00:32:23,071 Now astronomers are looking for quasars, 503 00:32:23,141 --> 00:32:26,474 the secret to finding more black holes 504 00:32:26,544 --> 00:32:29,104 and figuring out how they work. 505 00:32:29,180 --> 00:32:32,547 The Chandra observatory is a space telescope 506 00:32:32,617 --> 00:32:38,317 that can detect the powerful x-rays quasars send out. 507 00:32:38,389 --> 00:32:41,222 It's found thousands. 508 00:32:41,292 --> 00:32:43,760 These remarkable images show 509 00:32:43,828 --> 00:32:48,731 quasars of all shapes and sizes firing out into space. 510 00:32:52,804 --> 00:32:54,931 Each one is a signpost 511 00:32:55,006 --> 00:32:59,033 for a young galaxy with a new black hole at its center. 512 00:33:02,880 --> 00:33:05,872 These quasars will eventually calm down 513 00:33:05,950 --> 00:33:11,217 as their galaxy matures and takes its final shape. 514 00:33:11,289 --> 00:33:13,154 I guess the universe is a lot like people... 515 00:33:13,224 --> 00:33:14,589 active when they're young, 516 00:33:14,659 --> 00:33:16,991 a little bit quieter and more relaxed when they get older. 517 00:33:19,197 --> 00:33:22,166 We now know that supermassive black holes 518 00:33:22,233 --> 00:33:26,226 and the quasars they create control galaxies. 519 00:33:26,304 --> 00:33:30,263 Black holes are central to understanding how galaxies form. 520 00:33:30,341 --> 00:33:33,310 They're a key to understanding how they evolve with time. 521 00:33:33,378 --> 00:33:35,710 So, in fact, rather than being obscura, 522 00:33:35,780 --> 00:33:37,771 they're fundamental to our understanding 523 00:33:37,849 --> 00:33:39,578 of our galaxies and our universe. 524 00:33:39,650 --> 00:33:43,848 The only way to find out more about black holes 525 00:33:43,921 --> 00:33:45,889 is to get a good look at one. 526 00:33:45,957 --> 00:33:49,688 And since an up-close visit is, well, not a good idea, 527 00:33:49,761 --> 00:33:52,662 astronomers are trying to devise a way to take a picture 528 00:33:52,730 --> 00:33:56,530 of the supermassive black hole at the heart of our own galaxy. 529 00:33:56,601 --> 00:33:58,034 To get it, 530 00:33:58,102 --> 00:34:02,232 they'll need a telescope as large as Earth itself. 531 00:34:16,320 --> 00:34:18,254 There's a supermassive black hole 532 00:34:18,322 --> 00:34:21,814 at the center of the Milky Way. 533 00:34:24,162 --> 00:34:27,063 It's hidden by a dense cluster of stars 534 00:34:27,131 --> 00:34:29,622 circling the heart of the galaxy. 535 00:34:32,470 --> 00:34:36,907 But soon, we hope we'll be able to see it. 536 00:34:36,974 --> 00:34:40,341 Seeing is believing. 537 00:34:40,411 --> 00:34:43,574 It would be spectacular if we can go right up there, 538 00:34:43,648 --> 00:34:46,481 nose-to-nose with the event horizon 539 00:34:46,551 --> 00:34:49,884 of the black hole at the center of the Milky Way galaxy. 540 00:34:49,954 --> 00:34:53,185 And that's the Holy Grail. 541 00:34:53,257 --> 00:34:56,488 A supermassive black hole lies hidden 542 00:34:56,561 --> 00:34:58,586 at the center of most galaxies. 543 00:34:58,663 --> 00:35:00,392 We only know they're there 544 00:35:00,465 --> 00:35:03,366 because the stars around them are drawn in 545 00:35:03,434 --> 00:35:05,595 at millions of miles per hour. 546 00:35:05,670 --> 00:35:07,297 But there might still be a way 547 00:35:07,371 --> 00:35:10,863 to take a picture of the very edge of the black hole... 548 00:35:10,942 --> 00:35:13,103 the event horizon. 549 00:35:13,177 --> 00:35:16,908 Shep Doeleman and his team are trying to capture an image 550 00:35:16,981 --> 00:35:18,972 that shows its outline. 551 00:35:19,050 --> 00:35:21,245 We're essentially looking for the shadow, 552 00:35:21,319 --> 00:35:23,310 or the silhouette, of the black hole, 553 00:35:23,387 --> 00:35:26,823 within this cloud of gas that's swirling around it. 554 00:35:26,891 --> 00:35:30,554 This technique that we're exploiting 555 00:35:30,628 --> 00:35:33,597 is the best hope I think we have 556 00:35:33,664 --> 00:35:36,394 to actually image a region of the universe 557 00:35:36,467 --> 00:35:39,800 which has hitherto been completely invisible to us. 558 00:35:39,871 --> 00:35:42,101 Optical telescopes 559 00:35:42,173 --> 00:35:45,631 can't see the black hole directly. 560 00:35:45,710 --> 00:35:49,510 But the glowing, super-heated gas surrounding the black hole 561 00:35:49,580 --> 00:35:53,038 sends out radio waves that can be used to make an image. 562 00:35:55,119 --> 00:36:00,386 Huge radio telescopes pick up these signals from space. 563 00:36:00,458 --> 00:36:02,892 The antenna will move in azimuth and elevation. 564 00:36:09,534 --> 00:36:13,231 This one, at the M.I.T. Observatory near Boston, 565 00:36:13,304 --> 00:36:15,966 is more than 100 feet wide. 566 00:36:16,040 --> 00:36:20,101 It's big enough to detect very faint radio emissions 567 00:36:20,178 --> 00:36:25,081 from the black hole in our own galaxy, 25,000 light-years away. 568 00:36:25,149 --> 00:36:29,381 But it's not nearly big enough to capture an image. 569 00:36:29,453 --> 00:36:32,911 We need to take multiple copies of these telescopes, 570 00:36:32,990 --> 00:36:34,787 place them around the world 571 00:36:34,859 --> 00:36:39,387 to create a virtual telescope as large as the Earth itself. 572 00:36:39,463 --> 00:36:42,364 Doeleman's team will link up radio telescopes 573 00:36:42,433 --> 00:36:46,597 around the globe, from Hawaii to Chile to Africa. 574 00:36:52,810 --> 00:36:55,404 When the whole network is connected, 575 00:36:55,479 --> 00:36:59,575 they'll have a virtual dish over 10,000 miles across, 576 00:36:59,650 --> 00:37:04,144 with 500 times the power of a single telescope. 577 00:37:07,592 --> 00:37:10,083 They think it will be powerful enough 578 00:37:10,161 --> 00:37:12,721 to take a picture of the event horizon 579 00:37:12,797 --> 00:37:18,235 of the supermassive black hole at the center of the Milky Way. 580 00:37:18,302 --> 00:37:20,702 They're already picking up signals 581 00:37:20,771 --> 00:37:23,239 from the dark heart of our galaxy. 582 00:37:23,307 --> 00:37:25,798 When we saw the first detection, 583 00:37:25,876 --> 00:37:28,538 it was a moment where I just looked at the computer screen 584 00:37:28,613 --> 00:37:31,309 and said to myself, "My God, we've done it. 585 00:37:31,382 --> 00:37:34,249 We've actually seen something that's so small 586 00:37:34,318 --> 00:37:36,809 that it has to be coming from right around the event horizon." 587 00:37:38,389 --> 00:37:41,847 The signals are still too weak to give a complete picture, 588 00:37:41,926 --> 00:37:45,555 but Doeleman expects the images to improve 589 00:37:45,630 --> 00:37:50,533 as more telescopes come online over the next few years. 590 00:37:50,601 --> 00:37:55,834 Eventually, the outline of the black hole itself should emerge. 591 00:37:58,476 --> 00:38:03,641 But even a picture can't compare to witnessing it for yourself. 592 00:38:05,950 --> 00:38:09,283 In the distant future, we may have the technology 593 00:38:09,353 --> 00:38:13,756 to actually enter and pass through a black hole 594 00:38:13,824 --> 00:38:16,884 and maybe even survive the journey. 595 00:38:22,500 --> 00:38:25,799 Then we might finally answer the question... 596 00:38:25,870 --> 00:38:29,829 what lies at the heart of a black hole? 597 00:38:32,009 --> 00:38:33,374 Some scientists believe 598 00:38:33,444 --> 00:38:36,140 we could use black holes as a kind of portal, 599 00:38:36,213 --> 00:38:39,444 with the potential for travel across the universe. 600 00:38:39,517 --> 00:38:42,247 This is still very speculative, 601 00:38:42,320 --> 00:38:44,754 but the mathematics seem to indicate 602 00:38:44,822 --> 00:38:47,086 that as you fall through a black hole 603 00:38:47,158 --> 00:38:48,750 that you don't simply die... 604 00:38:48,826 --> 00:38:51,454 you fall right through a wormhole, 605 00:38:51,529 --> 00:38:56,159 which is a gateway, a shortcut through space and time. 606 00:38:56,233 --> 00:38:59,896 Perhaps we could simply rocket across the universe 607 00:38:59,970 --> 00:39:05,169 through a subway system that we call a black hole. 608 00:39:05,242 --> 00:39:09,474 If black holes are shortcuts through space and time, 609 00:39:09,547 --> 00:39:13,506 it could turn one of the coolest ideas from science fiction 610 00:39:13,584 --> 00:39:17,247 into reality. 611 00:39:17,321 --> 00:39:20,813 Time travel is possible, but not very practical. 612 00:39:20,891 --> 00:39:24,383 You see, the energy source, the material that you need 613 00:39:24,462 --> 00:39:26,930 to keep the throat of a wormhole open 614 00:39:26,997 --> 00:39:28,396 is something so ex otic 615 00:39:28,466 --> 00:39:31,299 that we cannot produce it in the laboratory. 616 00:39:31,369 --> 00:39:34,270 But if you could, it might be possible 617 00:39:34,338 --> 00:39:38,468 to exploit the power of black holes to visit yesterday. 618 00:39:40,111 --> 00:39:42,807 Perhaps our descendants in the future 619 00:39:42,880 --> 00:39:45,644 have already mastered this technology. 620 00:39:45,716 --> 00:39:47,843 So one day, if somebody knocks on your door 621 00:39:47,918 --> 00:39:49,249 and claims to be 622 00:39:49,320 --> 00:39:51,686 your great-great-great-great- great-great granddaughter, 623 00:39:51,756 --> 00:39:52,745 don't slam the door. 624 00:39:56,794 --> 00:40:01,094 Black holes might even be gateways to other universes. 625 00:40:01,165 --> 00:40:03,656 On the other side of a black hole, 626 00:40:03,734 --> 00:40:06,726 there could even be... a Big Bang. 627 00:40:10,040 --> 00:40:13,635 As a black hole collapses and matter falls into it, 628 00:40:13,711 --> 00:40:17,112 perhaps the matter is blown out the other side in a white hole. 629 00:40:17,181 --> 00:40:19,342 Doesn't that sound like the Big Bang? 630 00:40:25,022 --> 00:40:28,617 If a Big Bang is just the flip side of a black hole, 631 00:40:28,692 --> 00:40:32,685 this could be how our own universe was born. 632 00:40:34,498 --> 00:40:36,966 If you look at the equations for a black hole 633 00:40:37,034 --> 00:40:38,865 and put in the parameters of the universe... 634 00:40:38,936 --> 00:40:41,097 the mass of the universe, the size of the universe... 635 00:40:41,172 --> 00:40:42,161 bingo! 636 00:40:42,239 --> 00:40:43,604 You find that our universe 637 00:40:43,674 --> 00:40:46,234 actually solves the equations for a black hole. 638 00:40:46,310 --> 00:40:49,473 In other words, we could be inside an event horizon. 639 00:40:49,547 --> 00:40:54,985 Perhaps we are actually living inside a black hole. 640 00:40:55,052 --> 00:40:58,453 Every black hole might be the origin 641 00:40:58,522 --> 00:41:01,320 of an entirely separate universe. 642 00:41:01,392 --> 00:41:02,689 If that's true, 643 00:41:02,760 --> 00:41:07,356 there could be billions of universes out there... 644 00:41:10,835 --> 00:41:16,034 ...each one full of stars, planets, life. 645 00:41:16,106 --> 00:41:18,574 Whatever we figure out later, 646 00:41:18,642 --> 00:41:22,544 we know now that black holes are everywhere. 647 00:41:22,613 --> 00:41:23,773 They're bigger in size 648 00:41:23,848 --> 00:41:26,510 and more critical to the evolution of the universe 649 00:41:26,584 --> 00:41:28,711 than we ever imagined. 650 00:41:40,097 --> 00:41:41,962 Literally, our understanding 651 00:41:42,032 --> 00:41:44,023 of the universe that's important around us, 652 00:41:44,101 --> 00:41:46,433 the universe that's visible to telescopes, 653 00:41:46,504 --> 00:41:48,301 has been profoundly affected 654 00:41:48,372 --> 00:41:51,739 by our realization that black holes are everywhere. 655 00:41:54,712 --> 00:41:55,906 Once upon a time, 656 00:41:55,980 --> 00:41:57,572 people thought that black-hole physics 657 00:41:57,648 --> 00:42:00,742 was too fantastic to be true. 658 00:42:00,818 --> 00:42:03,378 And now they are center-stage. 659 00:42:03,454 --> 00:42:04,853 We now know they dominate 660 00:42:04,922 --> 00:42:07,117 the evolution of the universe itself. 661 00:42:09,093 --> 00:42:10,390 When I was a kid, 662 00:42:10,461 --> 00:42:12,691 black holes basically played a part in science fiction. 663 00:42:12,763 --> 00:42:14,230 It was always something to avoid. 664 00:42:14,298 --> 00:42:15,458 Your spaceship... 665 00:42:15,533 --> 00:42:17,433 you try to get around them before you get drawn in. 666 00:42:17,501 --> 00:42:19,492 But what we've learned since then 667 00:42:19,570 --> 00:42:21,731 is that black holes play a huge role 668 00:42:21,805 --> 00:42:24,296 and a huge number of roles in the universe. 669 00:42:27,244 --> 00:42:29,508 It's not an exaggeration to say 670 00:42:29,580 --> 00:42:33,277 that if black holes did not exist, we wouldn't be here. 671 00:42:33,350 --> 00:42:36,080 We literally owe our existence to black holes. 672 00:42:40,257 --> 00:42:43,624 The story's not over yet. 673 00:42:43,694 --> 00:42:46,254 There's still much more to be discovered 674 00:42:46,330 --> 00:42:51,199 about the mysterious objects called black holes... 675 00:42:51,268 --> 00:42:54,465 The masters of the universe.