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 00:00:59,020 --> 00:01:01,750 Black holes are the most mysterious objects 14 00:01:01,820 --> 00:01:03,480 in our universe. 15 00:01:03,560 --> 00:01:06,890 Their gravity is absolute. 16 00:01:09,100 --> 00:01:12,900 Nothing can escape. 17 00:01:12,970 --> 00:01:17,500 They can suck in whole galaxies. 18 00:01:17,570 --> 00:01:20,770 Black holes used to be science fiction. 19 00:01:20,840 --> 00:01:23,310 Now we know they're real. 20 00:01:23,380 --> 00:01:24,870 When I was a PhD student, 21 00:01:24,950 --> 00:01:28,310 people used to giggle when you'd hear about black holes. 22 00:01:28,380 --> 00:01:30,980 They're like unicorns, mythical creatures. 23 00:01:31,050 --> 00:01:32,750 We called this the "giggle factor." 24 00:01:32,820 --> 00:01:34,690 People would say, "Beam me up, Scotty." 25 00:01:34,760 --> 00:01:37,620 Well, no one is laughing anymore. 26 00:01:38,930 --> 00:01:41,260 So, they're not science fiction. 27 00:01:41,330 --> 00:01:43,390 Even though we've never landed in one, 28 00:01:43,460 --> 00:01:45,860 we have enough evidence to know that they're really out there. 29 00:01:51,810 --> 00:01:55,000 This image might not look like much to you and me, 30 00:01:55,080 --> 00:01:59,740 but to a scientist, it's proof that black holes exist. 31 00:01:59,810 --> 00:02:04,310 It's an actual movie of a black hole devouring a star 32 00:02:04,390 --> 00:02:06,950 in the constellation of Aquila. 33 00:02:07,020 --> 00:02:09,110 Black holes are messy eaters. 34 00:02:09,190 --> 00:02:11,490 The red spots you see are gas 35 00:02:11,560 --> 00:02:16,000 that's being spit out of the hole, into space. 36 00:02:16,060 --> 00:02:19,090 Eventually, over the next million years, 37 00:02:19,170 --> 00:02:23,970 this star will be eaten alive and disappear. 38 00:02:31,660 --> 00:02:34,000 A black hole is pretty much the end point of everything. 39 00:02:34,070 --> 00:02:36,500 It's the end point of a star. It's the end point of matter. 40 00:02:36,570 --> 00:02:39,090 It's the end point of energy. It's the end point of gravity. 41 00:02:39,170 --> 00:02:43,770 I mean, that's really it. That's the top of the scale. 42 00:02:47,910 --> 00:02:50,280 Although they have the power to destroy 43 00:02:50,350 --> 00:02:52,080 like nothing else in the universe, 44 00:02:52,150 --> 00:02:56,140 black holes also help build galaxies... 45 00:02:56,220 --> 00:03:00,160 a vital part of the great cosmic machine. 46 00:03:00,230 --> 00:03:02,160 Some astronomers think 47 00:03:02,230 --> 00:03:06,100 they could even be gateways to parallel universes. 48 00:03:12,300 --> 00:03:15,300 We are now entering the golden age of research 49 00:03:15,370 --> 00:03:16,770 in black-hole physics. 50 00:03:17,840 --> 00:03:19,440 They could be the key 51 00:03:19,510 --> 00:03:22,270 to understanding the birth of the universe, 52 00:03:22,350 --> 00:03:24,610 its formation, and then its death. 53 00:03:29,550 --> 00:03:31,520 Black holes really represent, 54 00:03:31,590 --> 00:03:33,820 in one sense, the frontier of modern astronomy. 55 00:03:33,890 --> 00:03:36,550 And they're changing our ideas about how galaxies form 56 00:03:36,630 --> 00:03:38,490 and, indeed, how the universe works. 57 00:03:38,560 --> 00:03:41,360 Their power comes 58 00:03:41,430 --> 00:03:45,160 from one of the primary forces in nature... gravity. 59 00:03:48,470 --> 00:03:50,700 I teach astronomy. 60 00:03:50,770 --> 00:03:52,260 And we teach our students 61 00:03:52,340 --> 00:03:56,110 that the fundamental principle of gravity is, "gravity sucks." 62 00:03:56,180 --> 00:03:59,670 Gravity keeps our feet on the ground 63 00:03:59,750 --> 00:04:02,780 and our planet orbiting around the Sun. 64 00:04:05,160 --> 00:04:10,650 But in a black hole, the force of gravity is off the charts... 65 00:04:10,730 --> 00:04:14,390 so strong, it sucks in anything nearby. 66 00:04:14,460 --> 00:04:19,930 It can even bend the light from distant stars. 67 00:04:20,000 --> 00:04:22,940 And if that light gets too close, 68 00:04:23,010 --> 00:04:25,410 the black hole swallows it. 69 00:04:25,480 --> 00:04:27,140 Think of it like this. 70 00:04:27,210 --> 00:04:30,010 Imagine a black hole as a waterfall. 71 00:04:30,080 --> 00:04:33,410 Gravity is the river flowing toward the falls, 72 00:04:33,480 --> 00:04:35,820 and a beam of light... the kayak. 73 00:04:35,890 --> 00:04:39,050 Upriver from the waterfall, the current is weak. 74 00:04:39,120 --> 00:04:42,610 The kayaker can paddle against it and get away. 75 00:04:42,690 --> 00:04:46,130 But closer to the waterfall, the current is stronger, 76 00:04:46,200 --> 00:04:51,100 and the kayaker struggles to escape. 77 00:04:51,170 --> 00:04:57,040 The edge of the waterfall is like the edge of a black hole. 78 00:04:57,110 --> 00:05:01,940 No matter how strong the kayaker is, he's going down. 79 00:05:02,010 --> 00:05:03,670 It's the same in space. 80 00:05:03,750 --> 00:05:06,840 The way black holes are really devastating 81 00:05:06,920 --> 00:05:09,180 is because when you get close to them, 82 00:05:09,250 --> 00:05:10,910 the gravity gets super-strong. 83 00:05:15,830 --> 00:05:18,760 So strong that they eat light. 84 00:05:18,830 --> 00:05:21,760 That's why black holes are black. 85 00:05:26,140 --> 00:05:28,630 A black hole is like a roach motel. 86 00:05:28,710 --> 00:05:31,610 Everything checks in. Nothing checks out. 87 00:05:35,850 --> 00:05:38,870 Anything that gets too close is doomed... 88 00:05:38,950 --> 00:05:44,580 planets, stars, even whole solar systems. 89 00:05:51,430 --> 00:05:54,870 And don't think this is some faraway phenomenon. 90 00:05:54,930 --> 00:05:57,200 Black holes are on the loose 91 00:05:57,270 --> 00:06:01,040 right here in our own cosmic neighborhood. 92 00:06:01,110 --> 00:06:03,510 We now know there are wandering nomads 93 00:06:03,580 --> 00:06:05,740 throughout the Milky Way galaxy... 94 00:06:05,810 --> 00:06:08,840 vagabonds throughout the galaxy, 95 00:06:08,910 --> 00:06:12,040 where black holes can come up right behind you 96 00:06:12,120 --> 00:06:14,810 and perhaps gobble you up, and they won't even burp. 97 00:06:16,890 --> 00:06:20,620 If one ever comes close, watch out. 98 00:06:20,690 --> 00:06:24,130 If a black hole found its way into our solar system, 99 00:06:24,700 --> 00:06:26,360 it would rip us apart. 100 00:06:26,430 --> 00:06:28,330 Any kind of black hole 101 00:06:28,400 --> 00:06:30,660 that could pass through the solar system 102 00:06:30,730 --> 00:06:32,400 would be pulling on all the planets 103 00:06:32,470 --> 00:06:33,600 harder than the Sun does. 104 00:06:33,670 --> 00:06:35,470 And so it's just gonna totally disrupt 105 00:06:35,540 --> 00:06:37,700 the gravitational balance of the solar system. 106 00:06:37,770 --> 00:06:43,180 The black hole would literally tear planets from their orbits 107 00:06:43,250 --> 00:06:45,370 and smash them into each other. 108 00:06:51,760 --> 00:06:55,780 It's just an epic disaster. It's a bull in a china shop. 109 00:07:00,160 --> 00:07:02,530 If it got close enough to, say, Jupiter, 110 00:07:02,600 --> 00:07:04,800 it could actually pull the moons of Jupiter 111 00:07:04,870 --> 00:07:06,030 away from the planet itself. 112 00:07:09,170 --> 00:07:11,440 It would just be flinging planets left and right 113 00:07:11,510 --> 00:07:13,770 everywhere as it whipped through the solar system, 114 00:07:13,850 --> 00:07:16,180 leaving disaster in its wake. 115 00:07:20,990 --> 00:07:23,950 If a black hole approached Earth, 116 00:07:24,020 --> 00:07:27,650 all that gravity would rip asteroids from their orbits 117 00:07:27,730 --> 00:07:29,820 and hurl them toward our planet. 118 00:07:38,540 --> 00:07:41,440 The Earth's surface would become an inferno. 119 00:07:41,510 --> 00:07:45,200 It would be the beginning of the end. 120 00:07:49,880 --> 00:07:52,480 First, it would swallow up the atmosphere, 121 00:07:52,550 --> 00:07:55,040 then the planet itself. 122 00:08:00,430 --> 00:08:03,330 Destroying an entire solar system 123 00:08:03,390 --> 00:08:05,760 is nothing to a black hole. 124 00:08:05,830 --> 00:08:10,730 But it's more than just a big, empty, sucking piece of space. 125 00:08:10,800 --> 00:08:13,640 It's incredibly heavy. 126 00:08:13,700 --> 00:08:18,110 To get an idea just how heavy and dense a black hole is, 127 00:08:18,180 --> 00:08:19,800 imagine the Earth. 128 00:08:19,880 --> 00:08:23,140 Now start to crush it... 129 00:08:25,820 --> 00:08:29,180 ...and keep crushing until it's packed so tight 130 00:08:29,250 --> 00:08:32,350 even the atoms themselves collapse. 131 00:08:35,260 --> 00:08:39,490 When the Earth crushes down to just 2 inches across, 132 00:08:39,560 --> 00:08:42,470 that's the density of a black hole. 133 00:08:42,530 --> 00:08:45,260 It would be the size of a golf ball, 134 00:08:45,340 --> 00:08:51,140 yet weigh the same as the Earth, with the same amount of gravity. 135 00:08:51,210 --> 00:08:55,010 What can make something that small, 136 00:08:55,080 --> 00:08:58,880 that dense, and that powerful? 137 00:08:58,950 --> 00:09:03,080 We don't have external forces, large pistons in the universe, 138 00:09:03,150 --> 00:09:04,680 to create black holes. 139 00:09:04,760 --> 00:09:07,450 So the only way the real black holes of the universe form 140 00:09:07,530 --> 00:09:09,490 is if gravity can do the job itself. 141 00:09:09,560 --> 00:09:13,360 There is only one place in the universe 142 00:09:13,430 --> 00:09:16,160 that generates that much gravity. 143 00:09:16,230 --> 00:09:18,960 And it's inside the largest stars. 144 00:09:19,040 --> 00:09:24,300 When massive stars 10 times heavier than our sun die, 145 00:09:24,380 --> 00:09:26,340 gravity crushes them, 146 00:09:26,410 --> 00:09:29,940 creating a huge explosion, a supernova. 147 00:09:40,220 --> 00:09:45,560 But some stars are even bigger than that. 148 00:09:45,630 --> 00:09:50,590 These supermassive stars weigh 100 times more than our sun 149 00:09:50,670 --> 00:09:53,470 and have 100 times more gravity. 150 00:09:53,540 --> 00:09:55,870 When one of these stars dies, 151 00:09:55,940 --> 00:10:01,610 it sets off the biggest explosion in the universe... 152 00:10:01,680 --> 00:10:03,810 A hypernova. 153 00:10:13,690 --> 00:10:18,030 This is the birth of a black hole. 154 00:10:24,500 --> 00:10:29,370 Our universe is full of stars. 155 00:10:29,440 --> 00:10:33,310 At the end of their lives, some die quietly. 156 00:10:33,380 --> 00:10:37,610 Others go out in spectacular explosions. 157 00:10:37,680 --> 00:10:43,090 And some give birth to black holes. 158 00:10:43,150 --> 00:10:45,020 If you have a star, 159 00:10:45,090 --> 00:10:48,320 a supermassive star that's 100 times the mass of the Sun, 160 00:10:48,390 --> 00:10:51,290 at the end of its life, the core runs out of fuel. 161 00:10:51,360 --> 00:10:53,190 There's nothing left to hold it up, 162 00:10:53,260 --> 00:10:55,730 and the core collapses down into a black hole. 163 00:10:55,800 --> 00:10:59,460 When that happens, the enormous gravity 164 00:10:59,540 --> 00:11:04,530 generated at the heart of supermassive stars runs wild. 165 00:11:07,480 --> 00:11:12,350 This is the dying star V.Y. Canis Majoris. 166 00:11:12,420 --> 00:11:16,940 It's more than a billion kilometers across. 167 00:11:20,190 --> 00:11:24,560 Like all stars, it's a giant nuclear-fusion reactor, 168 00:11:24,630 --> 00:11:26,960 pumping energy outward. 169 00:11:27,030 --> 00:11:32,470 At the same time, the star's extreme gravity crushes inward. 170 00:11:32,540 --> 00:11:34,500 For a few million years, 171 00:11:34,570 --> 00:11:38,600 fusion and gravity are locked in standoff. 172 00:11:38,680 --> 00:11:41,670 But when the star runs out of fuel, 173 00:11:41,750 --> 00:11:45,580 fusion stops and the stalemate ends. 174 00:11:45,650 --> 00:11:47,380 Gravity wins. 175 00:11:50,420 --> 00:11:52,010 In a millisecond, 176 00:11:52,090 --> 00:11:55,350 the core shrinks to a fraction of its original size 177 00:11:55,430 --> 00:11:59,490 and a baby black hole is born. 178 00:11:59,560 --> 00:12:01,090 Immediately, 179 00:12:01,170 --> 00:12:05,000 it starts to cannibalize what's left of the star. 180 00:12:05,070 --> 00:12:08,440 As matter swirls into the black hole, it gets incredibly hot. 181 00:12:08,510 --> 00:12:10,970 And there are magnetic forces and frictional forces, 182 00:12:11,040 --> 00:12:13,070 and it's just a witch's brew, a nightmare, 183 00:12:13,140 --> 00:12:15,840 what's going on right above the surface of the black hole. 184 00:12:15,910 --> 00:12:18,510 The new black hole in the middle 185 00:12:18,580 --> 00:12:21,480 keeps feeding on the body of the star around it. 186 00:12:21,550 --> 00:12:26,250 It eats the gas so fast, it chokes and coughs, 187 00:12:26,320 --> 00:12:29,490 blasting out huge beams of energy. 188 00:12:33,660 --> 00:12:36,790 They basically eat their way out from the star. 189 00:12:36,870 --> 00:12:38,630 This happens in milliseconds. 190 00:12:38,700 --> 00:12:41,470 It happens before the rest of the star even knows 191 00:12:41,540 --> 00:12:42,970 the core is gone. 192 00:12:43,040 --> 00:12:47,480 And so basically, the star is dead before it hits the ground. 193 00:12:51,150 --> 00:12:54,950 Finally, the star explodes. 194 00:12:57,690 --> 00:13:02,890 In one second, it blasts out 100 times more energy 195 00:13:02,960 --> 00:13:07,160 than our sun will produce over its entire life. 196 00:13:09,630 --> 00:13:14,370 What's left is a new black hole and two jets of energy 197 00:13:14,440 --> 00:13:19,030 hurtling through the universe at the speed of light. 198 00:13:19,110 --> 00:13:22,740 These jets are called "gamma-ray bursts." 199 00:13:28,190 --> 00:13:31,250 They're incredibly energetic events. 200 00:13:31,320 --> 00:13:33,590 In terms of raw energy and power, 201 00:13:33,660 --> 00:13:36,890 gamma ray bursts are second only to the Big Bang itself. 202 00:13:38,530 --> 00:13:41,460 Most of them last only a few seconds. 203 00:13:41,530 --> 00:13:44,970 And they fry anything in their way. 204 00:13:48,870 --> 00:13:52,170 They're so intense that if there was a gamma-ray burster 205 00:13:52,240 --> 00:13:55,210 in the region of our galaxy near our solar system, 206 00:13:55,280 --> 00:13:58,610 it could literally vaporize the entire planet. 207 00:13:58,680 --> 00:14:03,710 Fortunately, most gamma-ray bursts occur outside our galaxy. 208 00:14:10,730 --> 00:14:13,630 But they tell us something important 209 00:14:13,700 --> 00:14:18,660 about black holes and how our universe works. 210 00:14:18,740 --> 00:14:22,040 What we were seeing every time a gamma-ray burst went off 211 00:14:22,110 --> 00:14:24,730 was basically the birth cry of a black hole. 212 00:14:24,810 --> 00:14:29,940 By counting gamma-ray bursts, astronomers can figure out 213 00:14:30,010 --> 00:14:32,640 how many black holes are being created. 214 00:14:32,720 --> 00:14:36,910 In 2004, NASA launched the Swift probe 215 00:14:36,990 --> 00:14:40,390 to scan the universe for gamma-ray bursts. 216 00:14:40,460 --> 00:14:41,390 Five... 217 00:14:41,460 --> 00:14:42,430 four... 218 00:14:42,490 --> 00:14:43,460 three... 219 00:14:43,530 --> 00:14:44,590 two... 220 00:14:44,660 --> 00:14:46,720 one... We have ignition. 221 00:14:46,800 --> 00:14:50,130 And we have lift-off of NASA's Swift spacecraft, 222 00:14:50,200 --> 00:14:53,430 on a mission to study and understand gamma-ray bursts 223 00:14:53,500 --> 00:14:54,970 throughout the universe. 224 00:15:02,380 --> 00:15:05,400 This is the most powerful gamma-ray burst 225 00:15:05,480 --> 00:15:07,570 Swift has detected so far. 226 00:15:07,650 --> 00:15:11,550 The flash of light announces the birth of a new black hole 227 00:15:11,620 --> 00:15:14,090 on the other side of the universe. 228 00:15:18,360 --> 00:15:23,130 Swift can only look at a fraction of what's out there. 229 00:15:26,470 --> 00:15:31,270 Still, it detects at least one gamma-ray burst every day. 230 00:15:33,240 --> 00:15:37,840 That discovery rocked astronomy to its foundations. 231 00:15:40,280 --> 00:15:43,050 We once thought that black holes, like unicorns, 232 00:15:43,120 --> 00:15:45,680 could never be found. 233 00:15:45,760 --> 00:15:49,090 We now believe that there are perhaps billions of black holes 234 00:15:49,160 --> 00:15:50,390 in the night sky. 235 00:15:50,460 --> 00:15:53,090 When we look around our galaxy and other galaxies, 236 00:15:53,160 --> 00:15:57,960 it's clear that the universe is full of powerful black holes. 237 00:15:58,040 --> 00:16:00,530 Finding black holes is one thing. 238 00:16:00,600 --> 00:16:02,200 Figuring out how they work... 239 00:16:02,270 --> 00:16:04,370 that's a whole different ball game. 240 00:16:04,440 --> 00:16:07,140 The only way to find out is to visit one. 241 00:16:07,210 --> 00:16:11,550 You'd have to take a spacecraft across the vastness of space 242 00:16:11,620 --> 00:16:13,380 just to get close to it. 243 00:16:13,450 --> 00:16:17,610 Then you'd have to go inside the black hole. 244 00:16:17,690 --> 00:16:19,520 There, you'd find a place 245 00:16:19,590 --> 00:16:23,720 where reality breaks down and time stands still. 246 00:16:27,400 --> 00:16:30,700 There are billions of black holes in the universe. 247 00:16:30,770 --> 00:16:34,070 We can detect them with telescopes and satellites. 248 00:16:34,140 --> 00:16:38,730 But we don't actually know what they're like up-close. 249 00:16:38,810 --> 00:16:40,140 It's a long way off, 250 00:16:40,210 --> 00:16:42,770 but scientists are already speculating 251 00:16:42,850 --> 00:16:46,150 about a mission to a black hole... 252 00:16:46,220 --> 00:16:50,950 A one-way trip to the most dangerous place in the universe. 253 00:16:54,690 --> 00:16:56,130 Originally, 254 00:16:56,190 --> 00:17:01,030 physicists were horrified at the idea of black holes. 255 00:17:01,100 --> 00:17:02,620 They wanted to banish them, 256 00:17:02,700 --> 00:17:05,360 because the laws of physics, as we know them, 257 00:17:05,440 --> 00:17:08,340 seem to break down at the instant of a black hole. 258 00:17:08,410 --> 00:17:09,960 Time stops. 259 00:17:11,410 --> 00:17:14,170 Gravity becomes infinite. 260 00:17:14,240 --> 00:17:17,610 This is a nightmare. 261 00:17:17,680 --> 00:17:20,980 Obviously, we can't send humans anywhere near a black hole. 262 00:17:21,050 --> 00:17:23,710 But a robot? Well, sure. 263 00:17:23,790 --> 00:17:26,850 A robotic probe could transmit data back 264 00:17:26,920 --> 00:17:29,590 just before it goes over the edge. 265 00:17:29,660 --> 00:17:34,600 That edge of a black hole is called the "event horizon." 266 00:17:34,670 --> 00:17:36,790 It's the edge of time and space... 267 00:17:36,870 --> 00:17:40,430 at least, in the universe we know. 268 00:17:40,500 --> 00:17:42,500 We call the event horizon "event horizon" 269 00:17:42,570 --> 00:17:43,560 quite simply because 270 00:17:43,640 --> 00:17:45,400 it separates space into two regions. 271 00:17:48,210 --> 00:17:49,610 It's not a physical surface. 272 00:17:49,680 --> 00:17:52,980 You might not even notice it if you were falling through it, 273 00:17:53,050 --> 00:17:56,250 but ultimately, once you're inside of it, you're doomed. 274 00:17:56,320 --> 00:17:58,450 As you approach the event horizon, 275 00:17:58,520 --> 00:18:00,220 gravity gets stronger 276 00:18:00,290 --> 00:18:04,320 and very strange things start to happen. 277 00:18:04,400 --> 00:18:07,520 As you fall into a black hole feet-first, 278 00:18:07,600 --> 00:18:10,070 your feet are closer to the black hole. 279 00:18:10,130 --> 00:18:13,760 And so the gravity they feel is stronger. 280 00:18:13,840 --> 00:18:15,570 Your head is not quite as close, 281 00:18:15,640 --> 00:18:17,770 and so the gravity it feels is less. 282 00:18:17,840 --> 00:18:20,540 And basically, what happens is, you get stretched out. 283 00:18:20,610 --> 00:18:22,910 Your feet are being pulled much harder than your head, 284 00:18:22,980 --> 00:18:24,280 and you're like a piece of taffy 285 00:18:24,350 --> 00:18:26,080 being pulled between two strong people. 286 00:18:28,550 --> 00:18:30,610 As you get thinner and thinner and thinner, 287 00:18:30,690 --> 00:18:32,660 as you get closer and closer and closer, 288 00:18:32,720 --> 00:18:36,220 you're undergoing a process we call "spaghettification" 289 00:18:36,290 --> 00:18:40,250 because you're basically turned into a long, thin tube of pasta. 290 00:18:44,200 --> 00:18:47,660 Gravity would stretch our robotic probe to the limit, 291 00:18:47,740 --> 00:18:49,430 then rip it apart. 292 00:18:58,080 --> 00:19:00,520 But imagine if the probe was strong enough 293 00:19:00,580 --> 00:19:03,020 to survive and keep going. 294 00:19:05,960 --> 00:19:11,330 As it gets close to the event horizon, everything goes crazy. 295 00:19:11,400 --> 00:19:16,890 Gravity is so extreme, it stops time. 296 00:19:16,970 --> 00:19:19,230 We think of time as being endless. 297 00:19:19,300 --> 00:19:22,470 However, in a black hole, in some sense, time stops. 298 00:19:26,740 --> 00:19:29,710 This sounds like it's nuts, but that's the way it works. 299 00:19:29,780 --> 00:19:31,150 It's in the math. 300 00:19:31,220 --> 00:19:35,550 It's actually woven into the fabric of the universe itself. 301 00:19:35,620 --> 00:19:38,320 If you were to watch from a distance, 302 00:19:38,390 --> 00:19:40,720 the robot probe would seem to slow down 303 00:19:40,790 --> 00:19:43,260 as it gets closer to the black hole. 304 00:19:43,330 --> 00:19:47,060 Then it would appear to stop completely. 305 00:19:47,130 --> 00:19:50,190 The whole process might just take a brief moment. 306 00:19:50,270 --> 00:19:51,600 But from the outside, 307 00:19:51,670 --> 00:19:55,800 you appear to freeze and fall ever more slowly. 308 00:19:55,870 --> 00:19:58,500 You actually can never observe an object fall 309 00:19:58,580 --> 00:20:00,870 all the way through the event horizon. 310 00:20:00,940 --> 00:20:03,310 It literally freezes at the surface 311 00:20:03,380 --> 00:20:06,470 because its clock is going infinitely slowly 312 00:20:06,550 --> 00:20:07,980 compared to yours. 313 00:20:08,050 --> 00:20:12,890 In reality, the probe hasn't stopped at all. 314 00:20:12,960 --> 00:20:17,150 It keeps going and crosses the event horizon. 315 00:20:19,060 --> 00:20:21,960 If the probe points its cameras backwards, 316 00:20:22,030 --> 00:20:24,430 towards the entrance of the black hole, 317 00:20:24,500 --> 00:20:30,100 it will see light being sucked in. 318 00:20:30,170 --> 00:20:35,170 If it points the camera forward, at first it sees only black, 319 00:20:35,250 --> 00:20:38,580 but as it moves toward the heart of the black hole, 320 00:20:38,650 --> 00:20:43,420 it encounters the most bizarre place in the universe. 321 00:20:45,060 --> 00:20:48,990 The black hole's immense gravity pulls everything down 322 00:20:49,060 --> 00:20:52,390 to an unimaginably small point at its center. 323 00:20:52,460 --> 00:20:56,990 Scientists call it the "singularity." 324 00:20:57,070 --> 00:20:59,560 We really just don't know 325 00:20:59,640 --> 00:21:01,760 what happens at the center of a black hole. 326 00:21:01,840 --> 00:21:03,070 The densities are so great 327 00:21:03,140 --> 00:21:05,670 that the laws of physics break down, as we know them. 328 00:21:07,740 --> 00:21:10,440 A singularity is a point of infinite gravity, 329 00:21:10,510 --> 00:21:13,640 where space and time become meaningless. 330 00:21:13,720 --> 00:21:15,550 Now, that is ridiculous. 331 00:21:15,620 --> 00:21:20,420 A singularity is basically a word for saying "I don't know." 332 00:21:20,490 --> 00:21:22,750 It's a word for saying "I'm clueless." 333 00:21:27,030 --> 00:21:28,160 Even now, 334 00:21:28,230 --> 00:21:30,720 scientists can't really answer the question, 335 00:21:30,800 --> 00:21:32,100 "What is a black hole?" 336 00:21:32,170 --> 00:21:33,690 It's upsetting, a little bit, 337 00:21:33,770 --> 00:21:35,290 to think that there are objects out there 338 00:21:35,370 --> 00:21:37,700 that are breaking the laws of physics. 339 00:21:37,770 --> 00:21:40,110 There must be bigger laws 340 00:21:40,180 --> 00:21:42,010 that are being used by these black holes, 341 00:21:42,080 --> 00:21:43,940 that are being obeyed by these black holes, 342 00:21:44,010 --> 00:21:45,570 that we just don't understand yet. 343 00:21:48,090 --> 00:21:51,180 Okay, so, the one thing we do understand 344 00:21:51,260 --> 00:21:54,690 is that black holes are born from dying stars. 345 00:21:56,830 --> 00:22:00,290 And most are small... around 20 kilometers across. 346 00:22:03,640 --> 00:22:06,600 But now scientists have discovered 347 00:22:06,670 --> 00:22:09,900 that some black holes are much bigger. 348 00:22:09,970 --> 00:22:13,100 They're called "supermassive black holes." 349 00:22:13,180 --> 00:22:17,440 They're the same size as our entire solar system. 350 00:22:17,520 --> 00:22:23,010 And one of these monsters lies at the heart of our own galaxy. 351 00:22:28,560 --> 00:22:32,930 Our solar system lies in the Milky Way galaxy. 352 00:22:33,000 --> 00:22:37,590 It's made up of billions of stars, including our sun... 353 00:22:39,900 --> 00:22:42,960 ...all revolving around a mysterious region 354 00:22:43,040 --> 00:22:45,630 right at the center. 355 00:22:45,710 --> 00:22:48,940 Children ask the question... 356 00:22:49,010 --> 00:22:50,640 if the Moon goes around the Earth, 357 00:22:50,710 --> 00:22:52,010 the Earth goes around the Sun, 358 00:22:52,080 --> 00:22:53,740 then what does the Sun go around? 359 00:22:53,820 --> 00:22:55,220 It's a good question. 360 00:22:55,290 --> 00:22:57,580 And astronomers ask the same thing. 361 00:22:57,650 --> 00:22:59,680 Maybe there was something going on 362 00:22:59,760 --> 00:23:01,450 at the heart of the Milky Way... 363 00:23:01,530 --> 00:23:06,900 perhaps a black hole at the very center. 364 00:23:06,960 --> 00:23:11,020 But because we can't actually see a black hole, 365 00:23:11,100 --> 00:23:16,200 the best they could do was look for telltale signs. 366 00:23:16,270 --> 00:23:17,930 Using infrared telescopes, 367 00:23:18,010 --> 00:23:20,640 they looked at the middle of the galaxy 368 00:23:20,710 --> 00:23:24,010 and discovered a densely packed swarm 369 00:23:24,080 --> 00:23:25,910 of millions of stars. 370 00:23:25,980 --> 00:23:29,850 But they couldn't see what was at the center. 371 00:23:35,030 --> 00:23:39,520 One team has spent 15 years looking for clues. 372 00:23:44,200 --> 00:23:47,430 High above the clouds on Mauna Kea, in Hawaii, 373 00:23:47,500 --> 00:23:50,800 the giant Keck telescope has the power 374 00:23:50,870 --> 00:23:55,310 to see right through to the center of the Milky Way. 375 00:24:02,090 --> 00:24:04,710 The region which we have to study 376 00:24:04,790 --> 00:24:08,090 to prove that there's a black hole is incredibly small. 377 00:24:08,160 --> 00:24:09,750 It is absolutely the case 378 00:24:09,830 --> 00:24:12,350 of looking for a needle in a haystack, 379 00:24:12,430 --> 00:24:15,260 except we know exactly where the needle is. 380 00:24:17,130 --> 00:24:20,190 Andrea Ghez has spent countless nights 381 00:24:20,270 --> 00:24:22,530 scanning the center of the galaxy 382 00:24:22,610 --> 00:24:24,940 for signs of a black hole. 383 00:24:25,010 --> 00:24:26,810 To be able to do this experiment, 384 00:24:26,880 --> 00:24:28,240 one has to be able to see 385 00:24:28,310 --> 00:24:31,080 the stars that are very close to the center of the galaxy 386 00:24:31,150 --> 00:24:33,910 and to position them incredibly accurately. 387 00:24:33,980 --> 00:24:35,710 And this would be equivalent 388 00:24:35,790 --> 00:24:38,780 to me in Los Angeles looking at you in New York 389 00:24:38,860 --> 00:24:42,920 and seeing you be able to move your finger like this. 390 00:24:56,770 --> 00:24:58,640 As the Keck kicks into action, 391 00:24:58,710 --> 00:25:02,740 a laser beam detects tiny disturbances in the atmosphere 392 00:25:02,810 --> 00:25:05,180 that would distort the image. 393 00:25:07,920 --> 00:25:13,790 Motors then adjust the huge 30-foot mirror to compensate. 394 00:25:13,860 --> 00:25:16,020 The image is clear enough 395 00:25:16,090 --> 00:25:20,120 to track the stars at the heart of our galaxy. 396 00:25:22,470 --> 00:25:26,930 Ghez has taken thousands of images over the last 15 years. 397 00:25:27,000 --> 00:25:32,530 And what they reveal is amazing. 398 00:25:32,610 --> 00:25:35,270 The stars at the center of the galaxy 399 00:25:35,350 --> 00:25:38,210 are moving at millions of kilometers an hour. 400 00:25:44,690 --> 00:25:49,060 The center of the galaxy is a very extreme environment. 401 00:25:49,130 --> 00:25:51,030 The speeds with which stars move 402 00:25:51,090 --> 00:25:54,060 is much higher than anywhere else in our galaxy. 403 00:25:54,130 --> 00:25:56,890 And that is absolutely the signpost of the black hole. 404 00:26:02,240 --> 00:26:08,080 They look like tiny planets racing around an invisible sun. 405 00:26:08,140 --> 00:26:11,600 But they're not planets. They're stars. 406 00:26:11,680 --> 00:26:13,670 It takes a lot of gravity 407 00:26:13,750 --> 00:26:18,020 to swing huge stars around in such fast, tight orbits. 408 00:26:18,090 --> 00:26:23,050 There's only one thing in the universe with that much pull... 409 00:26:23,130 --> 00:26:28,120 a supermassive black hole. 410 00:26:28,200 --> 00:26:30,390 Watching these things shows the presence 411 00:26:30,470 --> 00:26:33,270 of a 4-million-times- the-mass-of-our-sun black hole, 412 00:26:33,340 --> 00:26:35,600 located right at the heart of our galaxy. 413 00:26:37,270 --> 00:26:39,440 It is a huge discovery. 414 00:26:39,510 --> 00:26:43,280 Everything in our galaxy, including our own solar system, 415 00:26:43,350 --> 00:26:48,010 orbits around a supermassive black hole. 416 00:26:48,080 --> 00:26:51,110 But the Milky Way isn't the only galaxy 417 00:26:51,190 --> 00:26:53,490 with a black hole in the middle. 418 00:26:53,560 --> 00:26:55,720 There are supermassive black holes 419 00:26:55,790 --> 00:26:59,190 at the heart of most galaxies in the universe. 420 00:26:59,260 --> 00:27:02,750 The Andromeda galaxy is our closest neighbor. 421 00:27:02,830 --> 00:27:06,270 It circles around a supermassive black hole 422 00:27:06,340 --> 00:27:11,040 weighing 140 million times more than our sun. 423 00:27:11,110 --> 00:27:14,470 Other galaxies, like this one, M87, 424 00:27:14,540 --> 00:27:20,480 have black holes weighing as much as 20 billion suns. 425 00:27:20,550 --> 00:27:23,110 How do black holes get so big, 426 00:27:23,190 --> 00:27:27,560 and what are they doing at the center of galaxies? 427 00:27:27,620 --> 00:27:33,030 For answers, we have to go back nearly 14 billion years 428 00:27:33,100 --> 00:27:37,030 to the beginning of the universe. 429 00:27:37,100 --> 00:27:38,760 Back then, 430 00:27:38,840 --> 00:27:43,400 the universe was filled with clouds of gas from the Big Bang. 431 00:27:44,970 --> 00:27:46,500 In some places, 432 00:27:46,580 --> 00:27:50,410 the gas was thick enough for millions of stars to form. 433 00:27:55,320 --> 00:27:58,480 Most of these new stars were supermassive. 434 00:27:58,550 --> 00:28:00,540 They burned hot and fast 435 00:28:00,620 --> 00:28:04,650 and then exploded, creating lots of black holes. 436 00:28:14,240 --> 00:28:17,000 The early universe was a wild-and-crazy place 437 00:28:17,070 --> 00:28:19,270 where huge regions of mass 438 00:28:19,340 --> 00:28:20,640 were collapsing catastrophically, 439 00:28:20,710 --> 00:28:21,970 producing black holes. 440 00:28:22,040 --> 00:28:24,740 And, in fact, the early universe might have been 441 00:28:24,810 --> 00:28:27,180 full of emerging black holes everywhere. 442 00:28:29,890 --> 00:28:32,580 Gravity pulled many of them together. 443 00:28:32,660 --> 00:28:34,920 All over the early universe, 444 00:28:34,990 --> 00:28:39,190 they merged, creating larger and larger black holes. 445 00:28:42,200 --> 00:28:45,930 Over hundreds of millions of years, each black hole grew, 446 00:28:46,000 --> 00:28:50,370 producing stronger gravity and pulling in more and more gas. 447 00:28:50,440 --> 00:28:55,040 New stars were born from the gas, forming primitive galaxies. 448 00:28:57,110 --> 00:29:00,910 But the black hole kept on sucking in gas, 449 00:29:00,980 --> 00:29:02,780 until it could take no more, 450 00:29:02,850 --> 00:29:06,910 igniting the most powerful flamethrower in the universe. 451 00:29:20,940 --> 00:29:24,300 A young galaxy is a vast cluster of stars, 452 00:29:24,370 --> 00:29:27,400 stars that formed from clouds of gas. 453 00:29:32,350 --> 00:29:34,820 At the center of the new galaxy 454 00:29:34,880 --> 00:29:39,290 is a young, supermassive black hole feeding on the gas, 455 00:29:39,360 --> 00:29:41,290 getting bigger and bigger. 456 00:29:41,360 --> 00:29:42,550 If you can imagine, 457 00:29:42,630 --> 00:29:45,490 when a galaxy is very young and still forming, 458 00:29:45,560 --> 00:29:48,330 there's a supermassive black hole forming at the core, 459 00:29:48,400 --> 00:29:50,330 and the gas is still falling into it 460 00:29:50,400 --> 00:29:51,870 and still forming the galaxy. 461 00:29:51,930 --> 00:29:54,230 Well, near that central black hole, 462 00:29:54,300 --> 00:29:55,930 things are getting very hot. 463 00:29:56,010 --> 00:29:57,630 That material is heating up. 464 00:29:57,710 --> 00:30:01,270 Gas is speeding into the black hole. 465 00:30:01,340 --> 00:30:03,780 But it overloads, 466 00:30:03,850 --> 00:30:08,510 and there is no room for all that excess hot gas. 467 00:30:08,580 --> 00:30:12,920 It has nowhere to go but out. 468 00:30:12,990 --> 00:30:18,050 It's blasted into space in huge jets of energy. 469 00:30:22,700 --> 00:30:26,160 Each jet is 20 times wider than our solar system 470 00:30:26,240 --> 00:30:30,400 and shoots clear through the galaxy. 471 00:30:30,470 --> 00:30:36,380 The supermassive black hole has ignited a quasar. 472 00:30:36,450 --> 00:30:38,140 Quasars are literally 473 00:30:38,210 --> 00:30:40,310 the brightest objects in the universe. 474 00:30:40,380 --> 00:30:43,380 They're so intense, they can outshine an entire galaxy. 475 00:30:43,450 --> 00:30:46,220 This is a real photograph 476 00:30:46,290 --> 00:30:50,090 of a real quasar in the galaxy M87, 477 00:30:50,160 --> 00:30:53,750 50 million light-years away. 478 00:30:57,230 --> 00:31:00,830 Quasars blast away huge quantities of gas 479 00:31:00,900 --> 00:31:02,840 from the surrounding galaxy... 480 00:31:05,540 --> 00:31:10,070 ...the equivalent of 10 Earths every minute. 481 00:31:13,520 --> 00:31:15,640 When you heat up a gas, 482 00:31:15,720 --> 00:31:17,810 it tends to expand and it blows outward. 483 00:31:17,890 --> 00:31:20,520 And it's sort of like a wind, but on a huge scale. 484 00:31:20,590 --> 00:31:22,560 And you get a black-hole wind, 485 00:31:22,630 --> 00:31:25,150 gas blowing out from the black hole. 486 00:31:25,230 --> 00:31:29,930 Black holes suck gas in. Quasars blow it out. 487 00:31:30,000 --> 00:31:34,560 But eventually there's no gas left to make stars, 488 00:31:34,640 --> 00:31:36,330 and the galaxy stops growing. 489 00:31:36,410 --> 00:31:39,140 So we think that the eventual size 490 00:31:39,210 --> 00:31:40,700 that a galaxy can achieve 491 00:31:40,780 --> 00:31:43,270 depends on the black hole in its center. 492 00:31:43,350 --> 00:31:44,870 The two are tied together. 493 00:31:46,850 --> 00:31:51,650 With no gas left to feed on, the quasar jets shrink and die. 494 00:31:53,120 --> 00:31:56,150 What's left is a supermassive black hole 495 00:31:56,230 --> 00:32:00,630 at the center of the galaxy, with a whole lot of young stars, 496 00:32:00,700 --> 00:32:04,630 just like our Milky Way back when it was young. 497 00:32:04,700 --> 00:32:07,360 Early on in the history of the Milky Way, 498 00:32:07,440 --> 00:32:10,770 when it was a young galaxy, we were probably a quasar. 499 00:32:10,840 --> 00:32:14,280 Probably every big galaxy was a quasar when it was young. 500 00:32:14,340 --> 00:32:15,830 But right now we're old enough 501 00:32:15,910 --> 00:32:17,880 that the galaxy has quieted down. 502 00:32:19,650 --> 00:32:23,520 Now astronomers are looking for quasars, 503 00:32:23,590 --> 00:32:26,920 the secret to finding more black holes 504 00:32:26,990 --> 00:32:29,550 and figuring out how they work. 505 00:32:29,630 --> 00:32:32,990 The Chandra observatory is a space telescope 506 00:32:33,060 --> 00:32:38,760 that can detect the powerful x-rays quasars send out. 507 00:32:38,830 --> 00:32:41,670 It's found thousands. 508 00:32:41,740 --> 00:32:44,210 These remarkable images show 509 00:32:44,270 --> 00:32:49,180 quasars of all shapes and sizes firing out into space. 510 00:32:53,250 --> 00:32:55,380 Each one is a signpost 511 00:32:55,450 --> 00:32:59,480 for a young galaxy with a new black hole at its center. 512 00:33:03,330 --> 00:33:06,320 These quasars will eventually calm down 513 00:33:06,400 --> 00:33:11,660 as their galaxy matures and takes its final shape. 514 00:33:11,730 --> 00:33:13,600 I guess the universe is a lot like people... 515 00:33:13,670 --> 00:33:15,030 active when they're young, 516 00:33:15,100 --> 00:33:17,440 a little bit quieter and more relaxed when they get older. 517 00:33:19,640 --> 00:33:22,610 We now know that supermassive black holes 518 00:33:22,680 --> 00:33:26,670 and the quasars they create control galaxies. 519 00:33:26,750 --> 00:33:30,710 Black holes are central to understanding how galaxies form. 520 00:33:30,790 --> 00:33:33,760 They're a key to understanding how they evolve with time. 521 00:33:33,820 --> 00:33:36,160 So, in fact, rather than being obscura, 522 00:33:36,230 --> 00:33:38,220 they're fundamental to our understanding 523 00:33:38,290 --> 00:33:40,020 of our galaxies and our universe. 524 00:33:40,600 --> 00:33:44,790 The only way to find out more about black holes 525 00:33:44,870 --> 00:33:46,830 is to get a good look at one. 526 00:33:46,900 --> 00:33:50,630 And since an up-close visit is, well, not a good idea, 527 00:33:50,710 --> 00:33:53,610 astronomers are trying to devise a way to take a picture 528 00:33:53,680 --> 00:33:57,480 of the supermassive black hole at the heart of our own galaxy. 529 00:33:57,550 --> 00:33:58,980 To get it, 530 00:33:59,050 --> 00:34:03,180 they'll need a telescope as large as Earth itself. 531 00:34:16,770 --> 00:34:18,700 There's a supermassive black hole 532 00:34:18,770 --> 00:34:22,260 at the center of the Milky Way. 533 00:34:24,610 --> 00:34:27,510 It's hidden by a dense cluster of stars 534 00:34:27,580 --> 00:34:30,070 circling the heart of the galaxy. 535 00:34:32,920 --> 00:34:37,350 But soon, we hope we'll be able to see it. 536 00:34:37,420 --> 00:34:40,790 Seeing is believing. 537 00:34:40,860 --> 00:34:44,020 It would be spectacular if we can go right up there, 538 00:34:44,090 --> 00:34:46,930 nose-to-nose with the event horizon 539 00:34:47,000 --> 00:34:50,330 of the black hole at the center of the Milky Way galaxy. 540 00:34:50,400 --> 00:34:53,630 And that's the Holy Grail. 541 00:34:53,700 --> 00:34:56,930 A supermassive black hole lies hidden 542 00:34:57,010 --> 00:34:59,030 at the center of most galaxies. 543 00:34:59,110 --> 00:35:00,840 We only know they're there 544 00:35:00,910 --> 00:35:03,810 because the stars around them are drawn in 545 00:35:03,880 --> 00:35:06,040 at millions of kilometers per hour. 546 00:35:06,120 --> 00:35:07,740 But there might still be a way 547 00:35:07,820 --> 00:35:11,310 to take a picture of the very edge of the black hole... 548 00:35:11,390 --> 00:35:13,550 the event horizon. 549 00:35:13,620 --> 00:35:17,350 Shep Doeleman and his team are trying to capture an image 550 00:35:17,430 --> 00:35:19,420 that shows its outline. 551 00:35:19,500 --> 00:35:21,690 We're essentially looking for the shadow, 552 00:35:21,760 --> 00:35:23,760 or the silhouette, of the black hole, 553 00:35:23,830 --> 00:35:27,270 within this cloud of gas that's swirling around it. 554 00:35:27,340 --> 00:35:31,000 This technique that we're exploiting 555 00:35:31,070 --> 00:35:34,040 is the best hope I think we have 556 00:35:34,110 --> 00:35:36,840 to actually image a region of the universe 557 00:35:36,910 --> 00:35:40,250 which has hitherto been completely invisible to us. 558 00:35:40,320 --> 00:35:42,550 Optical telescopes 559 00:35:42,620 --> 00:35:46,080 can't see the black hole directly. 560 00:35:46,160 --> 00:35:49,960 But the glowing, super-heated gas surrounding the black hole 561 00:35:50,030 --> 00:35:53,480 sends out radio waves that can be used to make an image. 562 00:35:55,560 --> 00:36:00,830 Huge radio telescopes pick up these signals from space. 563 00:36:00,900 --> 00:36:03,340 The antenna will move in azimuth and elevation. 564 00:36:09,980 --> 00:36:13,680 This one, at the M.I.T. Observatory near Boston, 565 00:36:13,750 --> 00:36:16,410 is more than 100 feet wide. 566 00:36:16,490 --> 00:36:20,550 It's big enough to detect very faint radio emissions 567 00:36:20,620 --> 00:36:25,530 from the black hole in our own galaxy, 25,000 light-years away. 568 00:36:25,590 --> 00:36:29,830 But it's not nearly big enough to capture an image. 569 00:36:29,900 --> 00:36:33,360 We need to take multiple copies of these telescopes, 570 00:36:33,440 --> 00:36:35,230 place them around the world 571 00:36:35,300 --> 00:36:39,830 to create a virtual telescope as large as the Earth itself. 572 00:36:39,910 --> 00:36:42,810 Doeleman's team will link up radio telescopes 573 00:36:42,880 --> 00:36:47,040 around the globe, from Hawaii to Chile to Africa. 574 00:36:53,260 --> 00:36:55,850 When the whole network is connected, 575 00:36:55,920 --> 00:37:00,020 they'll have a virtual dish over 10,000 kilometers across, 576 00:37:00,100 --> 00:37:04,590 with 500 times the power of a single telescope. 577 00:37:08,040 --> 00:37:10,530 They think it will be powerful enough 578 00:37:10,610 --> 00:37:13,170 to take a picture of the event horizon 579 00:37:13,240 --> 00:37:18,680 of the supermassive black hole at the center of the Milky Way. 580 00:37:18,750 --> 00:37:21,150 They're already picking up signals 581 00:37:21,220 --> 00:37:23,680 from the dark heart of our galaxy. 582 00:37:23,750 --> 00:37:26,240 When we saw the first detection, 583 00:37:26,320 --> 00:37:28,980 it was a moment where I just looked at the computer screen 584 00:37:29,060 --> 00:37:31,750 and said to myself, "My God, we've done it. 585 00:37:31,830 --> 00:37:34,690 We've actually seen something that's so small 586 00:37:34,760 --> 00:37:37,250 that it has to be coming from right around the event horizon." 587 00:37:38,830 --> 00:37:42,290 The signals are still too weak to give a complete picture, 588 00:37:42,370 --> 00:37:46,000 but Doeleman expects the images to improve 589 00:37:46,080 --> 00:37:50,980 as more telescopes come online over the next few years. 590 00:37:51,050 --> 00:37:56,280 Eventually, the outline of the black hole itself should emerge. 591 00:37:58,920 --> 00:38:04,090 But even a picture can't compare to witnessing it for yourself. 592 00:38:06,400 --> 00:38:09,730 In the distant future, we may have the technology 593 00:38:09,800 --> 00:38:14,200 to actually enter and pass through a black hole 594 00:38:14,270 --> 00:38:17,330 and maybe even survive the journey. 595 00:38:22,950 --> 00:38:26,240 Then we might finally answer the question... 596 00:38:26,320 --> 00:38:30,270 what lies at the heart of a black hole? 597 00:38:32,450 --> 00:38:33,820 Some scientists believe 598 00:38:33,890 --> 00:38:36,590 we could use black holes as a kind of portal, 599 00:38:36,660 --> 00:38:39,890 with the potential for travel across the universe. 600 00:38:39,960 --> 00:38:42,690 This is still very speculative, 601 00:38:42,770 --> 00:38:45,200 but the mathematics seem to indicate 602 00:38:45,270 --> 00:38:47,530 that as you fall through a black hole 603 00:38:47,600 --> 00:38:49,200 that you don't simply die... 604 00:38:49,270 --> 00:38:51,900 you fall right through a wormhole, 605 00:38:51,970 --> 00:38:56,600 which is a gateway, a shortcut through space and time. 606 00:38:56,680 --> 00:39:00,340 Perhaps we could simply rocket across the universe 607 00:39:00,420 --> 00:39:05,610 through a subway system that we call a black hole. 608 00:39:05,690 --> 00:39:09,920 If black holes are shortcuts through space and time, 609 00:39:09,990 --> 00:39:13,950 it could turn one of the coolest ideas from science fiction 610 00:39:14,030 --> 00:39:17,690 into reality. 611 00:39:17,770 --> 00:39:21,260 Time travel is possible, but not very practical. 612 00:39:21,340 --> 00:39:24,830 You see, the energy source, the material that you need 613 00:39:24,910 --> 00:39:27,380 to keep the throat of a wormhole open 614 00:39:27,440 --> 00:39:28,840 is something so exotic 615 00:39:28,910 --> 00:39:31,740 that we cannot produce it in the laboratory. 616 00:39:31,810 --> 00:39:34,720 But if you could, it might be possible 617 00:39:34,780 --> 00:39:38,910 to exploit the power of black holes to visit yesterday. 618 00:39:40,560 --> 00:39:43,250 Perhaps our descendants in the future 619 00:39:43,330 --> 00:39:46,090 have already mastered this technology. 620 00:39:46,160 --> 00:39:48,290 So one day, if somebody knocks on your door 621 00:39:48,360 --> 00:39:49,690 and claims to be 622 00:39:49,770 --> 00:39:52,130 your great-great-great-great- great-great granddaughter, 623 00:39:52,200 --> 00:39:53,190 don't slam the door. 624 00:39:57,240 --> 00:40:01,540 Black holes might even be gateways to other universes. 625 00:40:01,610 --> 00:40:04,100 On the other side of a black hole, 626 00:40:04,180 --> 00:40:07,170 there could even be... a Big Bang. 627 00:40:10,490 --> 00:40:14,080 As a black hole collapses and matter falls into it, 628 00:40:14,160 --> 00:40:17,560 perhaps the matter is blown out the other side in a white hole. 629 00:40:17,630 --> 00:40:19,790 Doesn't that sound like the Big Bang? 630 00:40:25,470 --> 00:40:29,060 If a Big Bang is just the flip side of a black hole, 631 00:40:29,140 --> 00:40:33,130 this could be how our own universe was born. 632 00:40:34,940 --> 00:40:37,410 If you look at the equations for a black hole 633 00:40:37,480 --> 00:40:39,310 and put in the parameters of the universe... 634 00:40:39,380 --> 00:40:41,540 the mass of the universe, the size of the universe... 635 00:40:41,620 --> 00:40:42,610 bingo! 636 00:40:42,680 --> 00:40:44,050 You find that our universe 637 00:40:44,120 --> 00:40:46,680 actually solves the equations for a black hole. 638 00:40:46,760 --> 00:40:49,920 In other words, we could be inside an event horizon. 639 00:40:49,990 --> 00:40:55,430 Perhaps we are actually living inside a black hole. 640 00:40:55,500 --> 00:40:58,900 Every black hole might be the origin 641 00:40:58,970 --> 00:41:01,770 of an entirely separate universe. 642 00:41:01,840 --> 00:41:03,130 If that's true, 643 00:41:03,210 --> 00:41:07,800 there could be billions of universes out there... 644 00:41:11,280 --> 00:41:16,480 ...each one full of stars, planets, life. 645 00:41:16,550 --> 00:41:19,020 Whatever we figure out later, 646 00:41:19,090 --> 00:41:22,990 we know now that black holes are everywhere. 647 00:41:23,060 --> 00:41:24,220 They're bigger in size 648 00:41:24,290 --> 00:41:26,960 and more critical to the evolution of the universe 649 00:41:27,030 --> 00:41:29,160 than we ever imagined. 650 00:41:40,540 --> 00:41:42,410 Literally, our understanding 651 00:41:42,480 --> 00:41:44,470 of the universe that's important around us, 652 00:41:44,550 --> 00:41:46,880 the universe that's visible to telescopes, 653 00:41:46,950 --> 00:41:48,750 has been profoundly affected 654 00:41:48,820 --> 00:41:52,180 by our realization that black holes are everywhere. 655 00:41:55,160 --> 00:41:56,350 Once upon a time, 656 00:41:56,430 --> 00:41:58,020 people thought that black-hole physics 657 00:41:58,090 --> 00:42:01,190 was too fantastic to be true. 658 00:42:01,260 --> 00:42:03,820 And now they are center-stage. 659 00:42:03,900 --> 00:42:05,300 We now know they dominate 660 00:42:05,370 --> 00:42:07,560 the evolution of the universe itself. 661 00:42:09,540 --> 00:42:10,840 When I was a kid, 662 00:42:10,910 --> 00:42:13,140 black holes basically played a part in science fiction. 663 00:42:13,210 --> 00:42:14,680 It was always something to avoid. 664 00:42:14,740 --> 00:42:15,900 Your spaceship... 665 00:42:15,980 --> 00:42:17,880 you try to get around them before you get drawn in. 666 00:42:17,950 --> 00:42:19,940 But what we've learned since then 667 00:42:20,020 --> 00:42:22,180 is that black holes play a huge role 668 00:42:22,250 --> 00:42:24,740 and a huge number of roles in the universe. 669 00:42:27,690 --> 00:42:29,950 It's not an exaggeration to say 670 00:42:30,030 --> 00:42:33,720 that if black holes did not exist, we wouldn't be here. 671 00:42:33,800 --> 00:42:36,530 We literally owe our existence to black holes. 672 00:42:40,700 --> 00:42:44,070 The story's not over yet. 673 00:42:44,140 --> 00:42:46,700 There's still much more to be discovered 674 00:42:46,780 --> 00:42:51,640 about the mysterious objects called black holes... 675 00:42:51,710 --> 00:42:54,910 The masters of the universe.