1 00:00:45,160 --> 00:00:47,219 (HEART BEATING) 2 00:00:47,429 --> 00:00:51,024 SAGAN: There is one experience that every human shares... 3 00:00:51,232 --> 00:00:53,496 ...of every language and culture: 4 00:00:53,701 --> 00:00:55,726 The experience of birth. 5 00:00:56,237 --> 00:00:59,866 Our recollections of birth are hazy at best. 6 00:01:00,074 --> 00:01:04,443 They have the feel and aura not so much of memories... 7 00:01:04,646 --> 00:01:08,844 ...as of mystical transfigurations. 8 00:01:09,050 --> 00:01:12,986 It would be astonishing if this profound early experience... 9 00:01:13,188 --> 00:01:15,782 ...did not influence our myths and religions... 10 00:01:15,990 --> 00:01:18,686 ...our philosophy and our science. 11 00:01:18,893 --> 00:01:23,694 The birth of a child evokes the mystery of other origins... 12 00:01:23,898 --> 00:01:26,389 ...the beginnings and ends of worlds... 13 00:01:26,668 --> 00:01:29,899 ...infinity and eternity. 14 00:01:31,105 --> 00:01:36,042 How did the universe arise? 15 00:01:36,878 --> 00:01:39,972 What was around before that? 16 00:01:40,815 --> 00:01:43,443 Might there have been no beginning? 17 00:01:43,651 --> 00:01:47,382 Could the universe be infinitely old? 18 00:01:47,589 --> 00:01:51,116 Are there boundaries to the cosmos? 19 00:01:51,493 --> 00:01:54,758 The current scientific story of the origin of the universe... 20 00:01:54,996 --> 00:01:59,365 ...begins with an explosion which made space itself expand. 21 00:01:59,567 --> 00:02:01,364 About 15 billion years ago... 22 00:02:01,569 --> 00:02:05,005 ...all the matter and energy that make up the observable universe... 23 00:02:05,206 --> 00:02:09,802 ...were concentrated into a space smaller than the head of a pin. 24 00:02:10,011 --> 00:02:14,744 The cosmos blew apart in one inconceivably colossal explosion: 25 00:02:14,949 --> 00:02:16,177 The big bang. 26 00:02:16,451 --> 00:02:20,683 The stuff of the universe, together with the fabric of space itself... 27 00:02:20,889 --> 00:02:24,552 ...began expanding in all directions as they do today. 28 00:02:24,759 --> 00:02:27,694 We can visualize this process with a three-dimensional grid... 29 00:02:27,896 --> 00:02:31,491 ...attached to the expanding fabric of space. 30 00:02:33,101 --> 00:02:36,696 The early cosmos was everywhere white-hot. 31 00:02:36,905 --> 00:02:40,136 But as time passed, the radiation expanded and cooled... 32 00:02:40,341 --> 00:02:44,573 ...and in ordinarily visible light, space became dark as it is today. 33 00:02:45,346 --> 00:02:48,907 But then little pockets of gas began to grow. 34 00:02:49,117 --> 00:02:51,881 Tendrils of gossamer clouds formed... 35 00:02:52,086 --> 00:02:56,352 ...colonies of great, lumbering, slowly spinning things... 36 00:02:56,558 --> 00:02:59,891 ...steadily brightening, each a kind of beast... 37 00:03:00,094 --> 00:03:03,530 ...composed of a hundred billion shining points. 38 00:03:07,168 --> 00:03:11,468 The largest recognizable structures in the universe had formed. 39 00:03:11,673 --> 00:03:16,007 We see them today. We ourselves inhabit some lost corner of one. 40 00:03:16,210 --> 00:03:18,610 We call them the galaxies. 41 00:03:18,813 --> 00:03:21,281 We inhabit a universe of galaxies. 42 00:03:21,482 --> 00:03:25,680 There are unstructured blobs, the irregular galaxies... 43 00:03:25,887 --> 00:03:28,754 ...globular or elliptical galaxies... 44 00:03:28,957 --> 00:03:33,257 ...and the graceful blue arms of spiral galaxies. 45 00:03:34,228 --> 00:03:36,128 We've been investigating the galaxies... 46 00:03:36,331 --> 00:03:40,597 ...their origins, evolution and motions for less than a century. 47 00:03:40,802 --> 00:03:43,464 These studies extend our understanding... 48 00:03:43,671 --> 00:03:46,731 ...to the farthest reaches of the universe. 49 00:03:48,810 --> 00:03:53,440 Our ship of the imagination carries us to that ultimate frontier. 50 00:03:53,648 --> 00:03:57,243 We view the cosmos on the grandest of scales. 51 00:03:57,452 --> 00:04:01,889 The majesty of the galaxies is revealed by science. 52 00:04:02,690 --> 00:04:06,922 There are many different ways in which stars are arrayed into galaxies. 53 00:04:10,498 --> 00:04:14,935 When, by chance, the face of a spiral galaxy is turned toward us... 54 00:04:15,136 --> 00:04:20,073 ...we see the spiral arms, made luminous by billions of stars. 55 00:04:20,274 --> 00:04:24,836 When, in other cases, the edge of a galaxy is towards us... 56 00:04:25,046 --> 00:04:27,276 ...we see the central lanes of gas and dust... 57 00:04:27,482 --> 00:04:29,780 ...from which the stars are forming. 58 00:04:31,619 --> 00:04:35,385 In barred spirals, a river of star stuff... 59 00:04:35,590 --> 00:04:37,820 ...extends through the galactic center... 60 00:04:38,026 --> 00:04:40,927 ...connecting opposite spiral arms. 61 00:04:41,663 --> 00:04:46,600 Elliptical galaxies come in giant and dwarf sizes. 62 00:04:49,270 --> 00:04:51,295 There are many mysterious galaxies... 63 00:04:51,506 --> 00:04:54,475 ...places where something has gone terribly wrong... 64 00:04:54,676 --> 00:04:56,837 ...where there are explosions and collisions... 65 00:04:57,045 --> 00:05:00,014 ...and streamers of gas and stars... 66 00:05:00,214 --> 00:05:03,342 ...bridges between the galaxies. 67 00:05:04,986 --> 00:05:08,217 The galaxies look rigid, unmoving. 68 00:05:08,423 --> 00:05:12,052 But we see them only for a single frame of the cosmic movie. 69 00:05:12,260 --> 00:05:15,593 Their parts are dissipating and reforming... 70 00:05:15,797 --> 00:05:18,766 ...on a time scale of hundreds of millions of years. 71 00:05:18,966 --> 00:05:23,062 A galaxy is a fluid made of billions of suns... 72 00:05:23,271 --> 00:05:26,240 ...all bound together by gravity. 73 00:05:27,075 --> 00:05:30,977 These giant galactic forms exist throughout the universe... 74 00:05:31,179 --> 00:05:34,671 ...and may be a common source of wonderment and instruction... 75 00:05:34,882 --> 00:05:38,113 ...for billions of species of intelligent life. 76 00:05:41,889 --> 00:05:46,826 Their evolution is governed everywhere by the same laws of physics. 77 00:05:50,865 --> 00:05:52,958 We need a computer to illustrate... 78 00:05:53,167 --> 00:05:55,533 ...the collective motion of so many stars... 79 00:05:55,737 --> 00:05:59,867 ...each under the gravitational influence of all the others. 80 00:06:03,711 --> 00:06:08,648 A billion years is here compressed into a few seconds. 81 00:06:11,452 --> 00:06:16,389 In some cases, spiral arms form all by themselves. 82 00:06:25,666 --> 00:06:26,963 In other cases... 83 00:06:27,168 --> 00:06:30,660 ...the close gravitational encounter of two galaxies... 84 00:06:30,872 --> 00:06:34,501 ...will draw out spiral arms. 85 00:06:40,515 --> 00:06:43,712 But when two nearby galaxies collide... 86 00:06:43,918 --> 00:06:46,614 ...like a bullet through a swarm of bees... 87 00:06:46,821 --> 00:06:48,755 ...the stars hardly collide at all. 88 00:06:48,956 --> 00:06:53,859 But the shapes of the galaxies can be severely distorted. 89 00:06:58,666 --> 00:07:03,262 A direct collision of two galaxies can last a hundred million years... 90 00:07:03,504 --> 00:07:06,064 ...and spill the constituent stars... 91 00:07:06,274 --> 00:07:09,835 ...careening through intergalactic space. 92 00:07:11,879 --> 00:07:16,373 When a dense, compact galaxy runs into a larger one face-on... 93 00:07:16,584 --> 00:07:19,951 ...it can produce one of the loveliest of the rare irregulars: 94 00:07:20,154 --> 00:07:22,213 A ring galaxy. 95 00:07:30,865 --> 00:07:33,197 Thousands of light-years across... 96 00:07:33,401 --> 00:07:35,699 ...a ring galaxy is set... 97 00:07:35,903 --> 00:07:39,498 ...against the velvet of intergalactic space. 98 00:07:43,477 --> 00:07:47,811 It's a temporary configuration of disrupted stars... 99 00:07:48,015 --> 00:07:51,314 ...a splash in the cosmic pond. 100 00:07:57,425 --> 00:08:00,326 Galaxies sometimes blow themselves up. 101 00:08:00,561 --> 00:08:04,463 The quasars, probably billions of light-years away... 102 00:08:04,665 --> 00:08:08,260 ...may be the colossal explosions of young galaxies. 103 00:08:08,469 --> 00:08:09,800 But we're not sure. 104 00:08:10,004 --> 00:08:13,633 Quasars are a mystery still. 105 00:08:17,912 --> 00:08:22,281 The galaxies reveal a universal order, beauty... 106 00:08:22,483 --> 00:08:27,011 ...but also violence on a scale never before imagined. 107 00:08:27,288 --> 00:08:31,156 The universe seems neither benign nor hostile... 108 00:08:31,359 --> 00:08:36,296 ...merely indifferent to the concerns of such creatures as we. 109 00:08:39,901 --> 00:08:43,803 Quasars may be monster versions of rapidly rotating pulsars... 110 00:08:44,005 --> 00:08:46,872 ...or due to multiple collisions of millions of stars... 111 00:08:47,074 --> 00:08:49,872 ...densely packed in the galactic core... 112 00:08:50,077 --> 00:08:55,014 ...or a chain reaction of supernova explosions in such a core. 113 00:08:57,485 --> 00:09:01,148 Some astronomers think a quasar is caused by millions of stars... 114 00:09:01,389 --> 00:09:05,655 ...falling into an immense black hole in the core of a galaxy. 115 00:09:05,893 --> 00:09:07,656 Something like a black hole... 116 00:09:07,895 --> 00:09:12,389 ...something very massive, very dense and very small... 117 00:09:12,600 --> 00:09:15,592 ...is ticking and purring away... 118 00:09:15,803 --> 00:09:18,966 ...in the cores of nearby galaxies. 119 00:09:28,049 --> 00:09:31,507 Even a well-behaved galaxy like the Milky Way... 120 00:09:31,719 --> 00:09:35,450 ...has its stirrings and its dances. 121 00:09:36,991 --> 00:09:41,018 The stars of the Milky Way move with systematic grace. 122 00:09:41,228 --> 00:09:44,527 The sun takes 250 million years... 123 00:09:44,765 --> 00:09:47,290 ...to go once around the core. 124 00:09:48,102 --> 00:09:50,127 The outer provinces of the galaxy... 125 00:09:50,338 --> 00:09:53,102 ...revolve more slowly than the inner regions. 126 00:09:53,307 --> 00:09:57,471 As a result, gas and dust pile up in spiral patterns. 127 00:09:57,678 --> 00:10:00,340 These places of greater density are where... 128 00:10:00,548 --> 00:10:02,607 ...young, hot, bright stars form... 129 00:10:02,883 --> 00:10:05,511 ...the stars which outline the spiral arms. 130 00:10:05,720 --> 00:10:09,315 These hot stars shine for only 10 million years or so... 131 00:10:09,523 --> 00:10:12,356 ...and then blow up. 132 00:10:13,928 --> 00:10:17,227 But as the stars which outline a spiral arm burn out... 133 00:10:17,465 --> 00:10:20,525 ...new, young stars are formed from the debris just behind them... 134 00:10:20,735 --> 00:10:23,761 ...and the spiral pattern persists. 135 00:10:25,906 --> 00:10:27,874 The sun, marked here with a circle... 136 00:10:28,075 --> 00:10:30,873 ...has been in and out of spiral arms often... 137 00:10:31,078 --> 00:10:33,569 ...in the 20 times it has gone around the Milky Way. 138 00:10:33,781 --> 00:10:38,115 In this epoch, we live at the edge of a spiral arm. 139 00:10:42,957 --> 00:10:46,825 We've looked at internal galactic motion on a small scale... 140 00:10:47,028 --> 00:10:49,622 ...across a million light-years or less. 141 00:10:49,830 --> 00:10:52,492 But the motion of the galaxies themselves... 142 00:10:52,700 --> 00:10:55,760 ...across billions of light-years is different. 143 00:10:55,970 --> 00:10:59,997 That motion is a relic of the big bang. 144 00:11:00,941 --> 00:11:04,308 The key to cosmology, the study of the entire universe... 145 00:11:04,512 --> 00:11:06,810 ...turns out to be a commonplace of nature... 146 00:11:07,014 --> 00:11:10,313 ...an experience of everyday life. 147 00:11:14,922 --> 00:11:17,789 Imagine a moving object sending out waves. 148 00:11:17,992 --> 00:11:19,892 It could be light waves... 149 00:11:20,127 --> 00:11:21,151 (WHISTLE BLOWS) 150 00:11:21,362 --> 00:11:25,059 ...it could be sound waves, it could be any kind of wave. 151 00:11:30,071 --> 00:11:32,198 When that moving object passes us... 152 00:11:32,406 --> 00:11:35,068 ...we sense a change in pitch. 153 00:11:35,309 --> 00:11:38,676 That's called the Doppler effect. 154 00:11:42,016 --> 00:11:43,813 If you're the engineer in the cab... 155 00:11:44,018 --> 00:11:47,351 ...the pitch of the whistle always sounds the same to you. 156 00:11:47,588 --> 00:11:51,547 That's because you're moving along with the source of the sound. 157 00:11:52,026 --> 00:11:55,086 But if you're standing alongside the track when the train passes... 158 00:11:55,296 --> 00:11:58,197 ...you hear that familiar shift in pitch: 159 00:11:58,432 --> 00:12:00,297 The Doppler shift. 160 00:12:05,906 --> 00:12:08,374 The reason this happens is easy to understand... 161 00:12:08,576 --> 00:12:11,272 ...once you visualize the waves. 162 00:12:11,979 --> 00:12:15,107 A stationary train sends out sound waves in perfect circles... 163 00:12:15,316 --> 00:12:17,614 ...like the ripples on a pond. 164 00:12:19,487 --> 00:12:21,682 Let's start the train again. 165 00:12:26,160 --> 00:12:30,187 Now, the waves spreading out ahead of it get squashed together... 166 00:12:30,397 --> 00:12:33,059 ...and those spreading out behind it get stretched apart. 167 00:12:33,300 --> 00:12:36,201 The compressed waves have a higher frequency or pitch... 168 00:12:36,403 --> 00:12:38,371 ...than the stretched-out waves. 169 00:12:39,907 --> 00:12:41,807 The same thing is true for light waves. 170 00:12:42,009 --> 00:12:45,809 Color is to light precisely what pitch is to sound. 171 00:12:46,413 --> 00:12:49,177 Compressed light waves are made bluer. They're blue-shifted. 172 00:12:49,383 --> 00:12:53,149 Stretched-out light waves are made redder. They're red-shifted. 173 00:12:55,856 --> 00:12:57,118 At the speed of a train... 174 00:12:57,324 --> 00:13:00,953 ...you can sense the change of pitch for sound, but not for light. 175 00:13:01,162 --> 00:13:05,098 The train is traveling about a million times too slow for that. 176 00:13:10,037 --> 00:13:13,370 It turns out that the Doppler effect for light waves... 177 00:13:13,607 --> 00:13:16,508 ...is the key to the cosmos. 178 00:13:18,112 --> 00:13:20,774 The evidence for this was gathered unexpectedly... 179 00:13:20,981 --> 00:13:25,850 ...by a former mule-team driver who never went beyond the eighth grade. 180 00:13:26,987 --> 00:13:28,852 During the second decade of this century... 181 00:13:29,056 --> 00:13:32,548 ...the world's largest telescope was being assembled on Mount Wilson... 182 00:13:32,793 --> 00:13:37,127 ...overlooking what were then the clear skies of Los Angeles. 183 00:13:37,831 --> 00:13:41,267 Large pieces of the telescope were hauled to the mountaintop... 184 00:13:41,468 --> 00:13:43,868 ...a job for mule teams. 185 00:13:46,840 --> 00:13:50,298 One of the drivers was a young man named Milton Humason... 186 00:13:50,511 --> 00:13:54,174 ...the ne'er-do-well son of a California banker. 187 00:13:54,415 --> 00:13:57,282 But he was bright and naturally curious about the equipment... 188 00:13:57,484 --> 00:13:59,281 ...he had carted up Mount Wilson. 189 00:13:59,486 --> 00:14:02,751 And after the telescope was completed in 1917... 190 00:14:02,957 --> 00:14:07,018 ...he managed to stay on here as janitor and electrician. 191 00:14:08,095 --> 00:14:11,963 One evening, so the story goes, the observatory night assistant was ill. 192 00:14:12,166 --> 00:14:14,794 Humason was asked to fill in. 193 00:14:21,909 --> 00:14:23,774 Humason was a gambling man... 194 00:14:23,978 --> 00:14:27,505 ...celebrated for his skill at poker and at the pool table. 195 00:14:27,715 --> 00:14:31,947 But his touch with the telescope was admired even more. 196 00:14:32,219 --> 00:14:35,552 He discovered he had a talent for using astronomical instruments. 197 00:14:35,789 --> 00:14:40,055 He became the virtuoso of the 100-inch telescope. 198 00:14:41,395 --> 00:14:43,829 In this instrument, light from distant galaxies... 199 00:14:44,031 --> 00:14:46,397 ...is focused on a glass photographic plate... 200 00:14:46,600 --> 00:14:50,627 ...by a great encased mirror 100 inches across. 201 00:14:52,206 --> 00:14:56,108 By the late 1920s, Humason was making observations himself. 202 00:14:56,310 --> 00:14:58,141 Mr. Nelson? 203 00:14:58,345 --> 00:15:00,939 NELSON: I'm in the coudé room, sir. 204 00:15:05,953 --> 00:15:08,513 SAGAN: Humason by now had his own night assistant... 205 00:15:08,756 --> 00:15:11,156 ...to help him with the observations. 206 00:15:13,227 --> 00:15:16,162 HUMASON: Afternoon, Mr. Nelson. -Good afternoon, Mr. Humason. 207 00:15:16,630 --> 00:15:17,995 We'll start at 6. 208 00:15:18,198 --> 00:15:21,099 I'll be making a spectrogram at the Cassegrain focus. 209 00:15:21,302 --> 00:15:22,667 Yes, sir. 210 00:15:23,937 --> 00:15:26,963 SAGAN: The telescope must be able to point with high accuracy... 211 00:15:27,174 --> 00:15:31,338 ...to a designated region of the sky, and to keep on pointing there. 212 00:15:32,880 --> 00:15:36,782 A machine weighing about 75 tons, as massive as a locomotive... 213 00:15:36,984 --> 00:15:40,750 ...must move with a precision greater than that of the finest pocket watch. 214 00:15:45,259 --> 00:15:48,353 Everything must be checked thoroughly. 215 00:15:53,233 --> 00:15:57,101 The electrical power system must work flawlessly. 216 00:16:04,478 --> 00:16:08,141 Hours before observations are to begin, the dome is opened... 217 00:16:08,349 --> 00:16:12,251 ...to allow the temperature inside and outside to be equalized. 218 00:16:19,026 --> 00:16:22,359 Humason prepared the sensitive photographic emulsions... 219 00:16:22,563 --> 00:16:24,588 ...sheathed in their metal holders... 220 00:16:24,798 --> 00:16:26,823 ...to capture with the giant telescope... 221 00:16:27,034 --> 00:16:30,265 ...the faint light from remote galaxies. 222 00:16:31,572 --> 00:16:34,097 This was part of a systematic program... 223 00:16:34,308 --> 00:16:38,438 ...which Humason and his mentor, the astronomer Edwin Hubble... 224 00:16:38,645 --> 00:16:40,943 ...were pursuing to measure the Doppler shift... 225 00:16:41,148 --> 00:16:44,413 ...of light from the most distant galaxies then known. 226 00:16:48,355 --> 00:16:51,119 But the most distant galaxies are very faint. 227 00:16:51,325 --> 00:16:54,385 That's why even with the largest telescope in the world... 228 00:16:54,595 --> 00:16:57,689 ...it was necessary to take very long time exposures... 229 00:16:57,898 --> 00:16:59,229 ...often lasting all night... 230 00:16:59,433 --> 00:17:02,459 ...and sometimes requiring several successive nights. 231 00:17:04,171 --> 00:17:07,732 Humason would give the night assistant the celestial coordinates... 232 00:17:07,941 --> 00:17:09,841 ...of the target galaxy. 233 00:17:18,952 --> 00:17:22,581 Through the long, cold night, he'd have to make fine adjustments... 234 00:17:22,790 --> 00:17:26,453 ...so the telescope would precisely track the target galaxy. 235 00:17:26,660 --> 00:17:30,027 The galaxy itself was too faint to see through the telescope... 236 00:17:30,264 --> 00:17:32,858 ...although it could be recorded photographically... 237 00:17:33,100 --> 00:17:34,465 ...with a long time exposure. 238 00:17:36,003 --> 00:17:39,530 So the telescope would be pointed at a nearby bright star... 239 00:17:39,740 --> 00:17:43,540 ...and then offset to a featureless patch of sky... 240 00:17:43,811 --> 00:17:45,779 ...from which, over the long night... 241 00:17:45,979 --> 00:17:49,813 ...the light from the unseen galaxy would slowly accumulate. 242 00:17:50,918 --> 00:17:53,546 The telescope focused the faint light from a galaxy... 243 00:17:53,754 --> 00:17:55,051 ...into the spectrometer... 244 00:17:55,255 --> 00:17:59,248 ...where it was spread out into its rainbow of constituent colors. 245 00:17:59,460 --> 00:18:03,396 The spectrum would be recorded on the little glass plates. 246 00:18:03,597 --> 00:18:07,328 Would you clamp in the drive and slue to the focus star, please? 247 00:18:08,302 --> 00:18:09,462 Are you clear? 248 00:18:09,937 --> 00:18:13,600 NELSON: I'm going to slue to the east. -Yes. I think I'm clear. 249 00:18:14,274 --> 00:18:16,265 HUMASON: Just take it easy. 250 00:18:35,496 --> 00:18:37,020 All right, I have it. 251 00:18:38,298 --> 00:18:41,597 Now, let's go to NGC 7-6-1-9. 252 00:18:41,802 --> 00:18:43,235 I'm clear. 253 00:18:46,840 --> 00:18:49,741 Going to do a 10-hour exposure. 254 00:18:52,980 --> 00:18:54,140 What time is it? 255 00:18:54,348 --> 00:18:56,179 7:15. 256 00:18:56,416 --> 00:18:57,815 HUMASON: Lights out, please. 257 00:19:03,223 --> 00:19:05,453 The dark slide is open. 258 00:19:16,937 --> 00:19:20,839 SAGAN: A large telescope views only a tiny patch of sky. 259 00:19:21,074 --> 00:19:24,441 As the Earth turns, a guide star or a galaxy... 260 00:19:24,645 --> 00:19:28,672 ...would drift out of the telescope's field of view in only a few minutes. 261 00:19:28,916 --> 00:19:31,851 Humason had to stay awake, tracking the galaxy... 262 00:19:32,085 --> 00:19:35,020 ...while elaborate machinery moved the telescope... 263 00:19:35,222 --> 00:19:39,158 ...slowly in the opposite direction, to compensate for Earth's rotation. 264 00:19:39,359 --> 00:19:42,294 The telescope is a kind of clock. 265 00:19:44,298 --> 00:19:45,492 HUMASON: How's the dome? 266 00:19:48,969 --> 00:19:50,402 You're clear. 267 00:19:55,008 --> 00:19:59,604 SAGAN: This work was difficult, routine, tedious... 268 00:19:59,813 --> 00:20:01,781 ...but although they didn't yet know it... 269 00:20:01,982 --> 00:20:04,951 ...Hubble and Humason were meticulously accumulating... 270 00:20:05,152 --> 00:20:08,053 ...the evidence for the big bang. 271 00:20:09,156 --> 00:20:11,818 They had found that the more distant the galaxy... 272 00:20:12,192 --> 00:20:16,492 ...the more its spectrum of colors was shifted to the red. 273 00:20:20,167 --> 00:20:21,657 HUMASON: All right, clear the telescope. 274 00:20:22,536 --> 00:20:24,470 I'm coming down now. 275 00:20:24,972 --> 00:20:28,339 If this red shift were due to the Doppler effect... 276 00:20:28,542 --> 00:20:31,204 ...the distant galaxies must be running away from us. 277 00:20:32,613 --> 00:20:34,171 At the end of his vigil... 278 00:20:34,381 --> 00:20:37,680 ...Humason would retrieve the tiny galactic spectrum... 279 00:20:37,884 --> 00:20:41,081 ...and carefully carry it down to be developed. 280 00:20:47,160 --> 00:20:49,219 Thank you, Mr. Nelson. 281 00:20:50,263 --> 00:20:52,788 I'm going to the darkroom now. 282 00:20:55,135 --> 00:20:57,103 -Good day. -Good day, sir. 283 00:21:01,942 --> 00:21:03,000 In this way... 284 00:21:03,243 --> 00:21:06,770 ...Humason found a red shift in almost every galaxy he examined... 285 00:21:06,980 --> 00:21:10,381 ...like the Doppler shift in the sound of a receding locomotive. 286 00:21:10,584 --> 00:21:14,714 And the farther away from us they were, the faster they were receding. 287 00:21:18,659 --> 00:21:22,390 Tied to the fabric of space, the outward rushing galaxies... 288 00:21:22,629 --> 00:21:26,861 ...were tracing the expansion of the universe itself. 289 00:21:27,067 --> 00:21:32,004 An awesome conclusion had been captured on these tiny glass slides. 290 00:21:33,040 --> 00:21:37,534 Humason and Hubble had discovered the big bang. 291 00:21:42,349 --> 00:21:44,544 At top and bottom are calibration lines... 292 00:21:44,751 --> 00:21:46,616 ...that Humason had earlier photographed. 293 00:21:46,820 --> 00:21:50,847 In the middle is the spectrum of a relatively nearby galaxy. 294 00:21:51,091 --> 00:21:55,027 Every element has a characteristic spectral fingerprint... 295 00:21:55,228 --> 00:21:57,696 ...a set of frequencies where light is absorbed. 296 00:21:57,931 --> 00:22:01,389 Prominent here are two dark lines in the violet... 297 00:22:01,601 --> 00:22:03,694 ...due to calcium in the atmospheres... 298 00:22:03,904 --> 00:22:06,134 ...of the hundreds of billions of stars... 299 00:22:06,339 --> 00:22:08,432 ...that constitute this galaxy. 300 00:22:08,642 --> 00:22:12,339 Nearby galaxies show very little Doppler shift. 301 00:22:13,080 --> 00:22:16,516 But when he recorded the spectrum of a fainter and more distant galaxy... 302 00:22:16,717 --> 00:22:19,447 ...he found the same telltale pair of lines... 303 00:22:19,653 --> 00:22:22,349 ...but shifted farther right toward the red. 304 00:22:22,556 --> 00:22:26,322 And when he examined a remote galaxy 4 billion light-years away... 305 00:22:26,526 --> 00:22:29,120 ...he found the lines were red-shifted even more. 306 00:22:29,329 --> 00:22:34,266 This galaxy must be receding at 200 million kilometers an hour. 307 00:22:36,937 --> 00:22:40,065 The painstaking observations of Milton Humason... 308 00:22:40,273 --> 00:22:43,140 ...astronomer and former mule-team driver... 309 00:22:43,343 --> 00:22:47,074 ...established the expansion of the universe. 310 00:22:53,386 --> 00:22:57,288 In discussing the large-scale structure of the cosmos... 311 00:22:57,491 --> 00:23:01,621 ...astronomers sometimes say that space is curved... 312 00:23:01,928 --> 00:23:06,865 ...or that the universe is finite but unbounded. 313 00:23:07,300 --> 00:23:09,131 Whatever are they talking about? 314 00:23:10,070 --> 00:23:12,368 Let's imagine that we are perfectly flat... 315 00:23:12,606 --> 00:23:14,836 ...I mean, absolutely flat... 316 00:23:15,041 --> 00:23:19,000 ...and that we live, appropriately enough, in Flatland... 317 00:23:19,212 --> 00:23:24,115 ...a land designed and named by Edwin Abbott... 318 00:23:24,317 --> 00:23:27,775 ...a Shakespearean scholar who lived in Victorian England. 319 00:23:28,054 --> 00:23:31,683 Everybody in Flatland is, of course, exceptionally flat. 320 00:23:32,058 --> 00:23:34,390 We have squares, circles, triangles... 321 00:23:34,628 --> 00:23:36,528 ...and we all scurry about... 322 00:23:36,730 --> 00:23:41,463 ...and we can go into our houses and do our flat business. 323 00:23:43,670 --> 00:23:48,403 Now, we have width and length... 324 00:23:48,608 --> 00:23:50,838 ...but no height at all. 325 00:23:51,077 --> 00:23:54,103 These cutouts have some height, but let's ignore that. 326 00:23:54,314 --> 00:23:57,249 Let's imagine that these are absolutely flat. 327 00:23:57,784 --> 00:24:01,686 That being the case, we know, us Flatlanders... 328 00:24:01,888 --> 00:24:04,755 ...about left-right and about forward-back... 329 00:24:04,958 --> 00:24:07,791 ...but we have never heard of up-down. 330 00:24:08,061 --> 00:24:11,758 Let us imagine that into Flatland... 331 00:24:11,965 --> 00:24:13,489 ...hovering above it... 332 00:24:13,700 --> 00:24:16,294 ...comes a strange three-dimensional creature... 333 00:24:16,503 --> 00:24:19,870 ...which, oddly enough, looks like an apple. 334 00:24:20,073 --> 00:24:22,234 The three-dimensional creature... 335 00:24:22,442 --> 00:24:25,878 ...sees an attractive congenial-looking square... 336 00:24:26,112 --> 00:24:28,546 ...watches it enter its house... 337 00:24:28,748 --> 00:24:33,685 ...and decides in a gesture of inter-dimensional amity... 338 00:24:33,954 --> 00:24:35,285 ...to say hello. 339 00:24:35,555 --> 00:24:37,989 "Hello," says the three-dimensional creature. 340 00:24:38,191 --> 00:24:41,683 "How are you? I am a visitor from the third dimension." 341 00:24:42,062 --> 00:24:46,999 Well, the poor square looks around his closed house... 342 00:24:47,367 --> 00:24:48,994 ...sees no one there... 343 00:24:49,202 --> 00:24:53,832 ...and what's more, has witnessed a greeting coming from his insides: 344 00:24:54,074 --> 00:24:56,406 A voice from within. 345 00:24:56,610 --> 00:25:00,876 He surely is getting a little worried about his sanity. 346 00:25:01,615 --> 00:25:03,583 The three-dimensional creature... 347 00:25:03,783 --> 00:25:07,844 ...is unhappy about being considered a psychological aberration... 348 00:25:08,088 --> 00:25:12,991 ...and so he descends to actually enter Flatland. 349 00:25:13,193 --> 00:25:17,254 Now, a three-dimensional creature exists in Flatland only partially... 350 00:25:17,464 --> 00:25:22,401 ...only a plane, a cross section through him can be seen. 351 00:25:22,702 --> 00:25:25,865 So when the three-dimensional creature first reaches Flatland... 352 00:25:26,072 --> 00:25:28,597 ...only its points of contact can be seen. 353 00:25:28,808 --> 00:25:33,745 And we'll represent that by stamping the apple in this ink pad... 354 00:25:34,481 --> 00:25:38,383 ...and placing that image in Flatland. 355 00:25:38,985 --> 00:25:43,115 And as the apple were to descend through... 356 00:25:43,323 --> 00:25:45,723 ...slither by Flatland... 357 00:25:45,926 --> 00:25:48,588 ...we would progressively see higher and higher slices... 358 00:25:48,795 --> 00:25:50,422 ...which we can represent... 359 00:25:50,630 --> 00:25:55,090 ...by cutting the apple. 360 00:25:56,903 --> 00:26:01,306 So the square, as time goes on... 361 00:26:01,508 --> 00:26:05,467 ...sees a set of objects mysteriously appear... 362 00:26:05,712 --> 00:26:09,239 ...from nowhere, and inside a closed room... 363 00:26:09,449 --> 00:26:12,475 ...and change their shape dramatically. 364 00:26:12,886 --> 00:26:16,253 His only conclusion could be that he's gone bonkers. 365 00:26:16,456 --> 00:26:20,517 Well, the apple might be a little annoyed at this conclusion... 366 00:26:20,760 --> 00:26:24,856 ...and so not such a friendly gesture from dimension to dimension... 367 00:26:25,065 --> 00:26:28,125 ...makes a contact with the square from below... 368 00:26:28,335 --> 00:26:30,030 ...and sends our flat creature... 369 00:26:30,270 --> 00:26:33,637 ...fluttering and spinning above Flatland. 370 00:26:33,840 --> 00:26:36,274 At first, the square has no idea what's happening. 371 00:26:36,476 --> 00:26:40,276 He's terribly confused. This is utterly outside his experience. 372 00:26:40,480 --> 00:26:43,381 But after a while, he comes to realize... 373 00:26:43,583 --> 00:26:48,418 ...that he is seeing inside closed rooms in Flatland. 374 00:26:48,621 --> 00:26:52,250 He is looking inside his fellow flat creatures: 375 00:26:52,459 --> 00:26:54,484 He is seeing Flatland from a perspective... 376 00:26:54,694 --> 00:26:57,254 ...no one has ever seen it before, to his knowledge. 377 00:26:57,464 --> 00:27:00,831 Getting into another dimension provides, as an incidental benefit... 378 00:27:01,034 --> 00:27:03,434 ...a kind of x-ray vision. 379 00:27:03,670 --> 00:27:08,232 Now our flat creature slowly descends to the surface... 380 00:27:08,441 --> 00:27:12,571 ...and his friends rush up to see him. 381 00:27:12,779 --> 00:27:15,907 From their point of view, he has mysteriously appeared from nowhere. 382 00:27:16,116 --> 00:27:20,485 He hasn't walked from somewhere else. He's come from some other place. 383 00:27:20,754 --> 00:27:23,416 They say, "For heaven's sake, what's happened to you?" 384 00:27:23,623 --> 00:27:25,853 And the poor square has to say: 385 00:27:26,092 --> 00:27:29,687 "Well, I was in some other mystic dimension... 386 00:27:29,896 --> 00:27:31,591 ...called 'Up."' 387 00:27:31,798 --> 00:27:35,928 And they will pat him on his side and comfort him... 388 00:27:36,136 --> 00:27:37,296 ...or else they'll ask: 389 00:27:37,504 --> 00:27:41,304 "Well, show us. Where is that third dimension? Point to it." 390 00:27:41,541 --> 00:27:44,908 And the poor square will be unable to comply. 391 00:27:45,211 --> 00:27:47,202 But maybe more interesting... 392 00:27:47,414 --> 00:27:50,247 ...is the other direction in dimensionality. 393 00:27:50,450 --> 00:27:53,385 What about the fourth dimension? 394 00:27:54,554 --> 00:27:57,182 Now, to approach that, let's consider a cube. 395 00:27:57,891 --> 00:27:59,984 We can imagine a cube in the following way: 396 00:28:00,193 --> 00:28:04,687 Take a line segment and move it at right angles to itself in equal length. 397 00:28:04,898 --> 00:28:06,422 That makes a square. 398 00:28:06,633 --> 00:28:09,659 Move that square in equal length at right angles to itself... 399 00:28:09,903 --> 00:28:11,928 ...and you have a cube. 400 00:28:12,138 --> 00:28:16,871 Now, this cube, we understand... 401 00:28:17,644 --> 00:28:19,441 ...casts a shadow. 402 00:28:22,415 --> 00:28:25,077 And that shadow we recognize... 403 00:28:25,285 --> 00:28:29,483 It's, you know, ordinarily drawn in third-grade classrooms... 404 00:28:29,856 --> 00:28:33,690 ...as two squares with their vertices connected. 405 00:28:33,893 --> 00:28:38,262 If we look at a three-dimensional object's shadow in two dimensions... 406 00:28:38,465 --> 00:28:41,923 ...we see that, in this case, not all the lines appear equal. 407 00:28:42,135 --> 00:28:43,966 Not all the angles are right angles. 408 00:28:44,204 --> 00:28:46,934 The 3-D object hasn't been perfectly represented... 409 00:28:47,140 --> 00:28:48,869 ...in its projection in two dimensions. 410 00:28:49,075 --> 00:28:53,876 But that's part of the cost of losing a dimension in the projection. 411 00:28:56,082 --> 00:28:59,381 Now, let's take this three-dimensional cube... 412 00:28:59,586 --> 00:29:04,285 ...and project it, carry it through a fourth physical dimension: 413 00:29:04,491 --> 00:29:08,222 Not that way, not that way, not that way. 414 00:29:08,428 --> 00:29:10,953 But at right angles to those three directions. 415 00:29:11,164 --> 00:29:12,791 I can't show you that direction. 416 00:29:12,999 --> 00:29:15,900 But imagine that there is a fourth physical dimension. 417 00:29:16,102 --> 00:29:20,562 In that case, we would generate a four-dimensional hyper-cube... 418 00:29:20,773 --> 00:29:22,798 ...which is also called a tesseract. 419 00:29:23,009 --> 00:29:26,172 I cannot show you a tesseract because I and you... 420 00:29:26,379 --> 00:29:28,347 ...are trapped in three dimensions. 421 00:29:28,581 --> 00:29:33,177 But what I can show you is the shadow in three dimensions... 422 00:29:33,419 --> 00:29:36,513 ...of a four-dimensional hyper-cube or tesseract. 423 00:29:36,723 --> 00:29:41,353 This is it, and you can see its two nested cubes... 424 00:29:41,594 --> 00:29:44,654 ...all the vertices connected by lines. 425 00:29:44,864 --> 00:29:48,925 And now the real tesseract in four dimensions... 426 00:29:49,135 --> 00:29:52,901 ...would have all lines of equal length and all angles right angles. 427 00:29:53,239 --> 00:29:58,006 That's not what we see here, but that's the penalty of projection. 428 00:29:58,611 --> 00:30:03,548 So you see, while we cannot imagine the world of four dimensions... 429 00:30:04,150 --> 00:30:08,382 ...we can certainly think about it perfectly well. 430 00:30:09,422 --> 00:30:12,721 Now, imagine a universe just like Flatland... 431 00:30:12,926 --> 00:30:17,226 ...truly two-dimensional and entirely flat in every direction. 432 00:30:17,463 --> 00:30:19,328 But with one exception: 433 00:30:20,066 --> 00:30:22,330 Unbeknownst to the inhabitants... 434 00:30:22,535 --> 00:30:24,833 ...their two-dimensional universe is curved... 435 00:30:25,038 --> 00:30:27,404 ...into a third physical dimension. 436 00:30:27,607 --> 00:30:29,973 Maybe into a sphere, but at any rate... 437 00:30:30,176 --> 00:30:33,077 ...into something entirely outside their experience. 438 00:30:34,948 --> 00:30:37,917 Locally, their universe still looks flat enough. 439 00:30:38,117 --> 00:30:42,178 But if one of them, much smaller and flatter than me... 440 00:30:42,422 --> 00:30:46,415 ...takes a very long walk along what seems to be a straight line... 441 00:30:46,626 --> 00:30:49,186 ...he would uncover a great mystery. 442 00:30:49,395 --> 00:30:52,831 Suppose he marked his starting point here... 443 00:30:53,032 --> 00:30:56,991 ...and set off to explore his universe. 444 00:30:58,104 --> 00:31:01,005 He never turns around and he never reaches an edge. 445 00:31:01,207 --> 00:31:04,699 He doesn't know that his apparently flat universe... 446 00:31:04,911 --> 00:31:08,210 ...is actually curved into an enormous sphere. 447 00:31:08,448 --> 00:31:12,111 He doesn't sense that he's walking around a globe. 448 00:31:13,987 --> 00:31:16,114 Why should his space be curved? 449 00:31:16,322 --> 00:31:18,415 Because this universe has so much matter... 450 00:31:18,625 --> 00:31:20,559 ...that it gravitationally warps space... 451 00:31:20,793 --> 00:31:23,591 ...closing it back on itself into a sphere. 452 00:31:23,963 --> 00:31:26,227 But our Flatlander doesn't know this. 453 00:31:26,466 --> 00:31:31,403 After a long while, he'll find he somehow returns to his starting point. 454 00:31:31,671 --> 00:31:34,640 There must be a third dimension. 455 00:31:34,841 --> 00:31:38,675 Our Flatlander couldn't imagine a third dimension... 456 00:31:38,911 --> 00:31:41,004 ...but he could sure deduce it. 457 00:31:41,214 --> 00:31:43,842 Increase all the dimensions in this story by one... 458 00:31:44,050 --> 00:31:46,712 ...and you have something like the situation... 459 00:31:46,919 --> 00:31:50,685 ...which many cosmologists think may actually apply to us. 460 00:31:50,923 --> 00:31:55,326 We are three-dimensional creatures trapped in three dimensions. 461 00:31:55,528 --> 00:31:59,191 We imagine our universe to be flat in three dimensions... 462 00:31:59,399 --> 00:32:03,597 ...but maybe it's curved into a fourth. 463 00:32:03,836 --> 00:32:07,602 We can talk about a fourth physical dimension, but we can't experience it. 464 00:32:07,807 --> 00:32:10,241 No one can point to the fourth dimension. 465 00:32:10,476 --> 00:32:14,537 There's left-right and there's forward-back. There's up-down... 466 00:32:14,747 --> 00:32:17,716 ...and there's some other directions... 467 00:32:17,917 --> 00:32:22,786 ...simultaneously at right angles to those familiar three dimensions. 468 00:32:23,690 --> 00:32:26,716 Now, imagine this universe is expanding. 469 00:32:27,727 --> 00:32:31,788 If we blow it up like a four- dimensional balloon, what happens? 470 00:32:31,998 --> 00:32:33,966 An astronomer on a given galaxy... 471 00:32:34,167 --> 00:32:37,659 ...thinks all the other galaxies are running away from him. 472 00:32:38,971 --> 00:32:42,304 The more distant the galaxy, the faster it seems to be moving. 473 00:32:42,508 --> 00:32:45,705 This is just what Humason and Hubble found. 474 00:32:47,847 --> 00:32:52,079 On the surface of this curved universe, there is no boundary or center. 475 00:32:52,285 --> 00:32:57,086 The universe can be both finite and unbounded. 476 00:33:00,860 --> 00:33:03,090 The red shift of the distant galaxies... 477 00:33:03,296 --> 00:33:05,526 ...seemed to imply to Humason's contemporaries... 478 00:33:05,765 --> 00:33:08,529 ...that we were at the center of an expanding universe... 479 00:33:08,735 --> 00:33:11,499 ...that our place in space was somehow privileged. 480 00:33:11,704 --> 00:33:13,171 But if the universe is expanding... 481 00:33:13,373 --> 00:33:16,035 ...whether or not it's curved into a fourth dimension... 482 00:33:16,275 --> 00:33:20,109 ...observers on every galaxy will see precisely the same thing: 483 00:33:20,313 --> 00:33:22,781 All the galaxies rushing away from them... 484 00:33:22,982 --> 00:33:27,885 ...as if they had made some dreadful intergalactic social blunder. 485 00:33:28,121 --> 00:33:31,613 If there's enough matter to close the universe gravitationally... 486 00:33:31,824 --> 00:33:35,055 ...then it's wrapped in on itself like a sphere. 487 00:33:36,796 --> 00:33:40,391 If there isn't enough matter to close the cosmos... 488 00:33:40,600 --> 00:33:43,000 ...then our universe has an open shape... 489 00:33:43,236 --> 00:33:46,637 ...extending forever in all directions. 490 00:33:47,140 --> 00:33:51,474 This saddle universe is only one of an infinite number... 491 00:33:51,677 --> 00:33:54,805 ...of possible kinds of open universes. 492 00:33:55,014 --> 00:33:57,915 Unlike such closed universes as the sphere... 493 00:33:58,117 --> 00:34:02,781 ...open universes have in them an infinite amount of space. 494 00:34:04,991 --> 00:34:07,459 If our universe is, in fact, closed off... 495 00:34:07,660 --> 00:34:11,152 ...then nothing can get out, not matter, not light. 496 00:34:11,364 --> 00:34:14,299 We would then be living inside a black hole. 497 00:34:14,534 --> 00:34:16,798 There is one possible way out, though: 498 00:34:17,003 --> 00:34:21,838 A hypothetical tunnel or wormhole through the next higher dimension... 499 00:34:22,041 --> 00:34:25,374 ...a place sucking in matter and light. 500 00:34:26,846 --> 00:34:30,646 Can we find such a wormhole? Could we survive the trip? 501 00:34:33,286 --> 00:34:36,016 We might emerge in some other place and time... 502 00:34:36,222 --> 00:34:37,849 ...perhaps in another universe... 503 00:34:38,057 --> 00:34:41,151 ...or perhaps somewhere else in our own. 504 00:34:43,563 --> 00:34:47,431 If you want to know what it's like inside a black hole... 505 00:34:47,633 --> 00:34:49,294 ...look around. 506 00:34:50,069 --> 00:34:55,006 But we don't yet know whether the universe is open or closed. 507 00:34:55,208 --> 00:34:57,733 More than that, some astronomers doubt... 508 00:34:57,944 --> 00:35:00,310 ...that the red shift of distant galaxies... 509 00:35:00,513 --> 00:35:02,071 ...is due to the Doppler effect. 510 00:35:02,415 --> 00:35:06,852 They are skeptical about the expanding universe and the big bang. 511 00:35:07,053 --> 00:35:11,149 Perhaps our descendants will regard our present ignorance... 512 00:35:11,357 --> 00:35:15,020 ...with as much sympathy as we feel to the ancients... 513 00:35:15,228 --> 00:35:17,924 ...for not knowing whether the Earth went around the sun. 514 00:35:18,631 --> 00:35:21,464 If the general picture, however, of a big bang... 515 00:35:21,667 --> 00:35:25,068 ...followed by an expanding universe is correct... 516 00:35:25,271 --> 00:35:26,829 ...what happened before that? 517 00:35:27,039 --> 00:35:30,475 Was the universe devoid of all matter... 518 00:35:30,676 --> 00:35:33,201 ...and then the matter suddenly somehow created? 519 00:35:33,412 --> 00:35:35,209 How did that happen? 520 00:35:35,715 --> 00:35:38,548 In many cultures, the customary answer... 521 00:35:38,751 --> 00:35:43,586 ...is that a god or gods created the universe out of nothing. 522 00:35:44,290 --> 00:35:47,691 But if we wish to pursue this question courageously... 523 00:35:47,894 --> 00:35:50,795 ...we must, of course, ask the next question: 524 00:35:50,997 --> 00:35:52,988 Where did God come from? 525 00:35:53,199 --> 00:35:55,963 If we decide that this is an unanswerable question... 526 00:35:56,168 --> 00:35:58,602 ...why not save a step and conclude... 527 00:35:58,804 --> 00:36:02,604 ...that the origin of the universe is an unanswerable question? 528 00:36:02,808 --> 00:36:06,437 Or if we say that God always existed... 529 00:36:06,646 --> 00:36:08,841 ...why not save a step and conclude... 530 00:36:09,048 --> 00:36:10,879 ...that the universe always existed? 531 00:36:11,083 --> 00:36:13,677 There's no need for a creation. It was always here. 532 00:36:13,886 --> 00:36:15,683 These are not easy questions. 533 00:36:15,888 --> 00:36:18,448 Cosmology brings us face to face... 534 00:36:18,658 --> 00:36:20,489 ...with the deepest mysteries... 535 00:36:20,693 --> 00:36:25,460 ...with questions that were once treated only in religion and myth. 536 00:36:37,076 --> 00:36:38,839 "Who knows for certain? 537 00:36:39,045 --> 00:36:41,138 Who shall here declare it? 538 00:36:41,347 --> 00:36:44,646 Whence was it born? Whence came creation? 539 00:36:45,251 --> 00:36:48,948 The gods are later than this world's formation. 540 00:36:49,522 --> 00:36:53,515 Who then can know the origins of the world? 541 00:36:55,528 --> 00:36:58,122 None knows whence creation arose... 542 00:36:58,331 --> 00:37:00,663 ...or whether He has or has not made it... 543 00:37:00,866 --> 00:37:04,666 ...He who surveys it from the lofty skies. 544 00:37:04,870 --> 00:37:06,531 Only He knows... 545 00:37:07,073 --> 00:37:10,133 ...or perhaps He knows not." 546 00:37:14,146 --> 00:37:17,547 These words are 3500 years old. 547 00:37:17,750 --> 00:37:19,581 They're taken from the Rig-Veda... 548 00:37:19,785 --> 00:37:22,481 ...a collection of early Sanskrit hymns. 549 00:37:22,688 --> 00:37:26,590 The most sophisticated ancient cosmological ideas came from Asia... 550 00:37:26,792 --> 00:37:29,056 ...and particularly from India. 551 00:37:29,261 --> 00:37:33,220 Here, there's a tradition of skeptical questioning... 552 00:37:33,432 --> 00:37:38,096 ...and unselfconscious humility before the great cosmic mysteries. 553 00:37:39,038 --> 00:37:41,563 Amidst the routine of daily life... 554 00:37:41,774 --> 00:37:44,538 ...in, say, the harvesting and winnowing of grain... 555 00:37:44,744 --> 00:37:47,144 ...people all over the world have wondered: 556 00:37:47,346 --> 00:37:51,009 Where did the universe come from? 557 00:37:51,217 --> 00:37:55,244 Asking this question is a hallmark of our species. 558 00:38:01,994 --> 00:38:03,859 There's a natural tendency to understand... 559 00:38:04,063 --> 00:38:08,090 ...the origin of the cosmos in familiar biological terms. 560 00:38:08,300 --> 00:38:10,393 The mating of cosmic deities... 561 00:38:10,603 --> 00:38:12,161 ...or the hatching of a cosmic egg... 562 00:38:12,371 --> 00:38:15,829 ...or maybe the intonation of some magic phrase. 563 00:38:24,216 --> 00:38:28,152 The big bang is our modern scientific creation myth. 564 00:38:28,354 --> 00:38:30,515 It comes from the same human need... 565 00:38:30,723 --> 00:38:32,623 ...to solve the cosmological riddle. 566 00:38:34,860 --> 00:38:36,521 Most cultures imagined the world... 567 00:38:36,729 --> 00:38:39,220 ...to be only a few hundred generations old. 568 00:38:39,432 --> 00:38:43,334 Hardly anyone guessed that the cosmos might be far older. 569 00:38:43,536 --> 00:38:45,834 But the ancient Hindus did. 570 00:38:51,043 --> 00:38:53,637 They, like every other society... 571 00:38:53,846 --> 00:38:57,441 ...noted and calibrated the cycles in nature. 572 00:38:58,718 --> 00:39:02,210 The rising and setting of the sun and the stars... 573 00:39:04,757 --> 00:39:06,816 ...the phases of the moon... 574 00:39:10,096 --> 00:39:12,428 ...the passing of the seasons. 575 00:39:23,042 --> 00:39:26,273 All over South India, an age-old ceremony... 576 00:39:26,479 --> 00:39:28,447 ...takes place every January... 577 00:39:28,647 --> 00:39:30,774 ...a rejoicing in the generosity of nature... 578 00:39:30,983 --> 00:39:33,451 ...in the annual harvesting of the crops. 579 00:39:33,652 --> 00:39:37,782 Every January, nature provides the rice to celebrate Pongal. 580 00:39:40,092 --> 00:39:44,529 Even the draft animals are given the day off and garlanded with flowers. 581 00:39:45,731 --> 00:39:49,462 (SPEAKING IN FOREIGN LANGUAGE) 582 00:39:56,375 --> 00:40:00,106 Colorful designs are painted on the ground to attract harmony... 583 00:40:00,312 --> 00:40:03,008 ...and good fortune for the coming year. 584 00:40:30,042 --> 00:40:34,979 Pongal, a simple porridge, a mixture of rice and sweet milk... 585 00:40:35,181 --> 00:40:38,344 ...symbolizes the harvest, the return of the seasons. 586 00:40:43,022 --> 00:40:47,049 (SHOUTING) 587 00:40:51,030 --> 00:40:54,522 However, this is not merely a harvest festival. 588 00:40:54,733 --> 00:40:59,898 It has ties to an elegant and much deeper cosmological tradition. 589 00:41:11,750 --> 00:41:14,810 The Pongal festival is a rejoicing in the fact... 590 00:41:15,020 --> 00:41:17,250 ...that there are cycles in nature. 591 00:41:17,890 --> 00:41:21,018 But how could such cycles come about unless the gods will them? 592 00:41:21,627 --> 00:41:24,790 And if there are cycles in the years of humans... 593 00:41:24,997 --> 00:41:29,400 ...might there not be cycles in the eons of the gods? 594 00:41:30,035 --> 00:41:32,560 Hinduism is the only one of the world's great faiths... 595 00:41:32,771 --> 00:41:37,071 ...dedicated to the idea that the cosmos itself... 596 00:41:37,276 --> 00:41:40,575 ...undergoes an immense, indeed, an infinite... 597 00:41:40,779 --> 00:41:43,714 ...number of deaths and rebirths. 598 00:41:59,698 --> 00:42:03,099 It is the only religion in which the time scales correspond... 599 00:42:03,302 --> 00:42:07,033 ...no doubt by accident, to those of modern scientific cosmology. 600 00:42:07,239 --> 00:42:10,436 Its cycles run from our ordinary day and night... 601 00:42:10,643 --> 00:42:13,271 ...to a day and night of Brahma... 602 00:42:13,479 --> 00:42:16,846 ...8.64 billion years long... 603 00:42:17,149 --> 00:42:20,448 ...longer than the age of the Earth or the sun... 604 00:42:20,653 --> 00:42:23,520 ...and about half the time since the big bang. 605 00:42:23,722 --> 00:42:27,624 And there are much longer time scales still. 606 00:42:36,268 --> 00:42:38,896 There is the deep and appealing notion... 607 00:42:39,104 --> 00:42:43,541 ...that the universe is but the dream of the god... 608 00:42:44,143 --> 00:42:48,273 ...who after 100 Brahma years... 609 00:42:48,480 --> 00:42:52,075 ...dissolves himself into a dreamless sleep... 610 00:42:52,451 --> 00:42:55,249 ...and the universe dissolves with him. 611 00:42:55,821 --> 00:43:00,520 Until, after another Brahma century, he stirs... 612 00:43:00,726 --> 00:43:04,162 ...recomposes himself and begins again... 613 00:43:04,363 --> 00:43:07,958 ...to dream the great cosmic lotus dream. 614 00:43:12,538 --> 00:43:15,769 Meanwhile, elsewhere... 615 00:43:15,975 --> 00:43:19,342 ...there are an infinite number of other universes... 616 00:43:19,545 --> 00:43:22,343 ...each with its own god... 617 00:43:22,548 --> 00:43:25,517 ...dreaming the cosmic dream. 618 00:43:27,720 --> 00:43:32,089 These great ideas are tempered by another... 619 00:43:32,291 --> 00:43:34,191 ...perhaps still greater. 620 00:43:34,660 --> 00:43:36,184 It is said... 621 00:43:36,495 --> 00:43:40,226 ...that men may not be the dreams of the gods... 622 00:43:40,432 --> 00:43:43,128 ...but rather that the gods... 623 00:43:43,335 --> 00:43:46,099 ...are the dreams of men. 624 00:43:51,076 --> 00:43:53,067 In India, there are many gods... 625 00:43:53,278 --> 00:43:56,714 ...and each god has many manifestations. 626 00:43:56,915 --> 00:44:00,214 These Chola bronzes cast in the 11th century... 627 00:44:00,419 --> 00:44:04,685 ...include several different incarnations of the god Shiva... 628 00:44:04,890 --> 00:44:07,381 ...seen here at his wedding. 629 00:44:08,627 --> 00:44:11,596 The most elegant and sublime of these bronzes... 630 00:44:11,797 --> 00:44:15,233 ...is a representation of the creation of the universe... 631 00:44:15,434 --> 00:44:17,834 ...at the beginning of each cosmic cycle: 632 00:44:18,404 --> 00:44:22,238 A motif known as the cosmic dance of Shiva. 633 00:44:22,941 --> 00:44:25,239 The god has four hands. 634 00:44:25,444 --> 00:44:28,504 In the upper right hand is a drum... 635 00:44:28,714 --> 00:44:32,946 ...whose sound is the sound of creation. 636 00:44:33,185 --> 00:44:36,348 In the upper left hand is a tongue of flame... 637 00:44:36,555 --> 00:44:41,083 ...a reminder that the universe, now newly created... 638 00:44:41,293 --> 00:44:46,196 ...will, billions of years from now, be utterly destroyed. 639 00:44:46,398 --> 00:44:49,333 Creation, destruction. 640 00:45:13,692 --> 00:45:17,184 These profound and lovely ideas... 641 00:45:17,396 --> 00:45:20,490 ...are central to ancient Hindu beliefs... 642 00:45:20,699 --> 00:45:25,636 ...as exemplified in this Chola temple at Darasuram. 643 00:45:26,638 --> 00:45:31,132 They're a kind of premonition of modern astronomical ideas. 644 00:45:31,643 --> 00:45:35,374 Without doubt, the universe has been expanding since the big bang... 645 00:45:35,581 --> 00:45:40,143 ...but it is, by no means, clear that it will continue to expand forever. 646 00:45:40,352 --> 00:45:44,584 If there is less than a certain amount of matter in the universe... 647 00:45:44,790 --> 00:45:48,419 ...then the mutual gravitation of the receding galaxies... 648 00:45:48,627 --> 00:45:51,858 ...will be insufficient to stop the expansion... 649 00:45:52,064 --> 00:45:55,033 ...and the universe will run away forever. 650 00:45:55,400 --> 00:45:58,426 But if there is more matter than we can see... 651 00:45:58,637 --> 00:46:01,629 ...hidden away in black holes, say... 652 00:46:01,840 --> 00:46:05,241 ...or in hot but invisible gas between the galaxies... 653 00:46:05,444 --> 00:46:07,912 ...then the universe holds together... 654 00:46:08,113 --> 00:46:11,276 ...and partakes of a very Indian succession of cycles... 655 00:46:11,483 --> 00:46:14,281 ...expansion followed by contraction... 656 00:46:14,486 --> 00:46:19,048 ...cosmos upon cosmos, universes without end. 657 00:46:19,291 --> 00:46:21,851 If we live in such an oscillating universe... 658 00:46:22,060 --> 00:46:24,722 ...the big bang is not the creation of the cosmos... 659 00:46:24,930 --> 00:46:27,490 ...but merely the end of the previous cycle... 660 00:46:27,699 --> 00:46:32,568 ...the destruction of the last incarnation of the cosmos. 661 00:46:33,672 --> 00:46:36,232 Neither of these modern cosmologies... 662 00:46:36,441 --> 00:46:38,932 ...may be altogether to our liking. 663 00:46:39,211 --> 00:46:44,046 In one cosmology, the universe is created somehow... 664 00:46:44,249 --> 00:46:47,548 ...from nothing 15 to 20 billion years ago... 665 00:46:47,853 --> 00:46:49,582 ...and expands forever... 666 00:46:49,788 --> 00:46:53,485 ...the galaxies mutually receding until the last one... 667 00:46:53,692 --> 00:46:57,492 ...disappears over our cosmic horizon. 668 00:46:57,829 --> 00:47:02,198 Then the galactic astronomers are out of business... 669 00:47:02,401 --> 00:47:07,338 ...the stars cool and die, matter itself decays... 670 00:47:07,606 --> 00:47:09,437 ...and the universe becomes... 671 00:47:09,641 --> 00:47:14,101 ...a thin, cold haze of elementary particles. 672 00:47:14,313 --> 00:47:17,714 In the other, the oscillating universe... 673 00:47:17,916 --> 00:47:20,646 ...the cosmos has no beginning and no end... 674 00:47:20,852 --> 00:47:23,218 ...and we are in the midst of an infinite cycle... 675 00:47:23,422 --> 00:47:27,358 ...of cosmic deaths and rebirths with no information... 676 00:47:27,559 --> 00:47:31,359 ...trickling through the cusps of the oscillation. 677 00:47:31,563 --> 00:47:35,624 Nothing of the galaxies, stars, planets... 678 00:47:35,834 --> 00:47:37,768 ...life forms, civilizations... 679 00:47:37,970 --> 00:47:41,337 ...evolved in the previous incarnation of the universe... 680 00:47:41,540 --> 00:47:43,770 ...trickles through the cusp... 681 00:47:43,976 --> 00:47:45,807 ...flitters past the big bang... 682 00:47:46,011 --> 00:47:48,775 ...to be known in our universe. 683 00:47:53,919 --> 00:47:57,218 The death of the universe in either cosmology... 684 00:47:57,422 --> 00:47:59,822 ...may seem a little depressing. 685 00:48:00,025 --> 00:48:04,291 But we may take some solace in the time scales involved. 686 00:48:04,496 --> 00:48:09,433 These events will take tens of billions of years or more. 687 00:48:09,701 --> 00:48:14,070 Human beings, or our descendants, whoever they might be... 688 00:48:14,273 --> 00:48:18,141 ...can do a great deal of good in tens of billions of years... 689 00:48:18,343 --> 00:48:21,312 ...before the cosmos dies. 690 00:48:39,064 --> 00:48:41,089 If the universe truly oscillates... 691 00:48:41,300 --> 00:48:45,464 ...if the modern scientific version of the old Hindu cosmology is valid... 692 00:48:45,671 --> 00:48:48,196 ...then still stranger questions arise. 693 00:48:48,407 --> 00:48:51,069 Some scientists think that when a red shift... 694 00:48:51,276 --> 00:48:53,437 ...is followed by blue shift... 695 00:48:53,645 --> 00:48:56,580 ...causality will be inverted... 696 00:48:56,782 --> 00:49:00,013 ...and effects will precede causes. 697 00:49:00,352 --> 00:49:02,411 First, the ripples spread out... 698 00:49:02,621 --> 00:49:04,680 ...from a point on the water's surface. 699 00:49:04,890 --> 00:49:08,326 Then I throw the stone into the pond. 700 00:49:12,197 --> 00:49:16,463 Some scientists wonder, in an oscillating universe... 701 00:49:16,668 --> 00:49:19,762 ...about what happens at the cusps... 702 00:49:19,971 --> 00:49:24,601 ...at the transition from contraction to expansion. 703 00:49:24,810 --> 00:49:28,610 Some think that the laws of nature are then randomly reshuffled... 704 00:49:28,814 --> 00:49:32,181 ...that the physics and chemistry we have in this universe... 705 00:49:32,384 --> 00:49:35,444 ...represent only one of an infinite range... 706 00:49:35,654 --> 00:49:38,680 ...of possible natural laws. 707 00:49:40,192 --> 00:49:41,819 It is easy to see... 708 00:49:42,027 --> 00:49:44,552 ...that only a restricted range of laws of nature... 709 00:49:44,763 --> 00:49:48,665 ...are consistent with galaxies and stars, planets... 710 00:49:48,867 --> 00:49:51,097 ...life and intelligence. 711 00:49:51,303 --> 00:49:53,066 If the laws of nature are... 712 00:49:53,271 --> 00:49:56,434 ...randomly reshuffled at the cusps... 713 00:49:56,942 --> 00:49:59,410 ...then it is only the most extraordinary coincidence... 714 00:49:59,611 --> 00:50:03,274 ...that the cosmic slot machine has this time come up... 715 00:50:03,482 --> 00:50:06,849 ...with a universe consistent with us. 716 00:50:07,419 --> 00:50:11,549 Do we live in a universe which expands forever... 717 00:50:11,757 --> 00:50:16,694 ...or in one where there is a nested set of infinite cycles? 718 00:50:17,462 --> 00:50:19,760 There's a way to find out the answer... 719 00:50:19,965 --> 00:50:22,593 ...not by mysticism, but through science... 720 00:50:22,801 --> 00:50:24,462 ...by making an accurate census... 721 00:50:24,669 --> 00:50:28,161 ...of the total amount of matter in the universe... 722 00:50:31,042 --> 00:50:35,411 ...or by seeing to the very edge of the cosmos. 723 00:50:45,924 --> 00:50:49,951 Radio telescopes are able to detect distant quasars... 724 00:50:50,162 --> 00:50:52,027 ...billions of light-years away... 725 00:50:52,230 --> 00:50:55,666 ...expanding with the fabric of space. 726 00:50:58,603 --> 00:51:00,730 By looking far out into space... 727 00:51:00,939 --> 00:51:03,806 ...we are also looking far back into time... 728 00:51:04,009 --> 00:51:06,637 ...back toward the horizon of the universe... 729 00:51:06,845 --> 00:51:10,076 ...back toward the epoch of the big bang. 730 00:51:11,516 --> 00:51:13,711 Radio telescopes have even detected... 731 00:51:13,919 --> 00:51:16,479 ...the cosmic background radiation. 732 00:51:16,688 --> 00:51:20,852 The fires of the big bang cooled and red-shifted... 733 00:51:21,059 --> 00:51:24,620 ...faintly echoing down the corridors of time. 734 00:51:33,638 --> 00:51:35,970 This is the very large array... 735 00:51:36,174 --> 00:51:39,837 ...a collection of 17 separate radio telescopes... 736 00:51:40,045 --> 00:51:41,808 ...all working collectively... 737 00:51:42,013 --> 00:51:44,743 ...in a remote region of New Mexico. 738 00:51:44,950 --> 00:51:48,977 Modern radio telescopes are exquisitely sensitive. 739 00:51:49,187 --> 00:51:52,645 A distant quasar is so faint... 740 00:51:52,858 --> 00:51:56,760 ...that its received radiation by some such telescope... 741 00:51:56,962 --> 00:52:01,729 ...amounts to maybe a quadrillionth of a watt. 742 00:52:02,100 --> 00:52:06,264 In fact, and this is a reasonably stunning piece of information... 743 00:52:06,471 --> 00:52:08,939 ...the total amount of energy ever received... 744 00:52:09,140 --> 00:52:11,734 ...by all the radio telescopes on the planet Earth... 745 00:52:11,943 --> 00:52:16,437 ...is less than the energy of a single snowflake... 746 00:52:16,648 --> 00:52:18,513 ...striking the ground. 747 00:52:18,884 --> 00:52:22,012 In detecting the cosmic background radiation... 748 00:52:22,220 --> 00:52:24,484 ...in counting quasars... 749 00:52:24,689 --> 00:52:27,715 ...in searching for intelligent signals from space... 750 00:52:27,926 --> 00:52:31,589 ...radio astronomers are dealing with amounts of energy... 751 00:52:31,796 --> 00:52:33,457 ...which are barely there at all. 752 00:52:39,971 --> 00:52:44,340 These radio telescopes, rising like giant flowers... 753 00:52:44,543 --> 00:52:46,067 ...from the New Mexico desert... 754 00:52:46,278 --> 00:52:49,270 ...are monuments to human ingenuity. 755 00:52:52,450 --> 00:52:55,476 The faint radio waves are collected, focused... 756 00:52:55,687 --> 00:52:59,316 ...assembled and amplified, and then converted... 757 00:52:59,524 --> 00:53:04,291 ...into pictures of nebulae, galaxies and quasars. 758 00:53:06,865 --> 00:53:09,333 If you had eyes that worked in radio light... 759 00:53:09,534 --> 00:53:12,025 ...they'd probably be bigger than wagon wheels... 760 00:53:12,237 --> 00:53:14,728 ...and this is the universe you'd see. 761 00:53:16,841 --> 00:53:19,105 An elliptical galaxy, for example... 762 00:53:19,311 --> 00:53:23,407 ...leaving behind it a long wake glowing in radio waves. 763 00:53:27,452 --> 00:53:30,478 Radio waves reveal a universe of quasars... 764 00:53:30,689 --> 00:53:34,352 ...interacting galaxies, titanic explosions. 765 00:53:40,332 --> 00:53:43,495 Every time we use another kind of light to view the cosmos... 766 00:53:43,702 --> 00:53:46,694 ...we open a new door of perception. 767 00:53:49,608 --> 00:53:53,135 As the murmurs from the edge of the cosmos slowly accumulate... 768 00:53:53,345 --> 00:53:56,212 ...our understanding grows. 769 00:54:01,953 --> 00:54:05,980 This is an exploration of the ancient and the invisible... 770 00:54:06,191 --> 00:54:08,421 ...a continuing human inquiry... 771 00:54:08,627 --> 00:54:12,188 ...into the grand cosmological questions. 772 00:54:23,675 --> 00:54:26,143 Another important recent finding... 773 00:54:26,344 --> 00:54:29,973 ...was made by x-ray observatories in Earth orbit. 774 00:54:30,181 --> 00:54:34,242 Artificial satellites launched to view the sky... 775 00:54:34,452 --> 00:54:38,252 ...not in ordinary visible light, not in radio waves... 776 00:54:38,456 --> 00:54:40,424 ...but in x-ray light. 777 00:54:40,625 --> 00:54:43,788 There seems to be an immense cloud... 778 00:54:43,995 --> 00:54:46,259 ...of extremely hot hydrogen... 779 00:54:46,464 --> 00:54:50,662 ...glowing in x-rays between some galaxies. 780 00:54:50,869 --> 00:54:53,337 Now, if this amount of intergalactic matter... 781 00:54:53,538 --> 00:54:56,666 ...were typical of all clusters of galaxies... 782 00:54:56,875 --> 00:55:01,608 ...then there may be just enough matter to close the cosmos... 783 00:55:01,813 --> 00:55:06,375 ...and to trap us forever in an oscillating universe. 784 00:55:10,855 --> 00:55:13,415 If the cosmos is closed... 785 00:55:13,625 --> 00:55:17,527 ...there's a strange, haunting, evocative possibility... 786 00:55:17,729 --> 00:55:21,790 ...one of the most exquisite conjectures in science or religion. 787 00:55:22,000 --> 00:55:24,400 It's entirely undemonstrated... 788 00:55:24,602 --> 00:55:28,265 ...it may never be proved, but it's stirring. 789 00:55:28,473 --> 00:55:33,035 Our entire universe, to the farthest galaxy, we are told... 790 00:55:33,244 --> 00:55:35,576 ...is no more than a closed electron... 791 00:55:35,780 --> 00:55:39,181 ...in a far grander universe we can never see. 792 00:55:39,384 --> 00:55:41,716 That universe is only an elementary particle... 793 00:55:41,920 --> 00:55:46,414 ...in another still greater universe and so on forever. 794 00:55:46,791 --> 00:55:50,420 Also, every electron in our universe, it is claimed... 795 00:55:50,628 --> 00:55:53,028 ...is an entire miniature cosmos... 796 00:55:53,231 --> 00:55:57,930 ...containing galaxies and stars and life and electrons. 797 00:55:58,136 --> 00:56:01,765 Every one of those electrons contains a still smaller universe... 798 00:56:01,973 --> 00:56:05,932 ...an infinite regression up and down. 799 00:56:09,714 --> 00:56:12,114 Every human generation has asked... 800 00:56:12,317 --> 00:56:15,218 ...about the origin and fate of the cosmos. 801 00:56:15,420 --> 00:56:19,117 Ours is the first generation with a real chance... 802 00:56:19,324 --> 00:56:22,157 ...of finding some of the answers. 803 00:56:22,761 --> 00:56:24,126 One way or another... 804 00:56:24,329 --> 00:56:28,663 ...we are poised at the edge of forever. 805 00:56:37,976 --> 00:56:42,470 Except for planetary exploration, the study of galaxies and cosmology... 806 00:56:42,680 --> 00:56:46,047 ...what this episode was about, have undergone the greatest advances... 807 00:56:46,251 --> 00:56:48,446 ...since Cosmos was first broadcast. 808 00:56:48,653 --> 00:56:51,486 For one thing, at last we have a good photograph... 809 00:56:51,689 --> 00:56:53,520 ...of our own Milky Way galaxy... 810 00:56:53,725 --> 00:56:56,785 ...about 100,000 light-years across. 811 00:56:57,128 --> 00:56:58,390 Here it is. 812 00:57:03,401 --> 00:57:06,598 It was taken by NASA's Coby satellite. 813 00:57:06,805 --> 00:57:09,774 We see it edge on, of course, since we're embedded... 814 00:57:09,974 --> 00:57:11,908 ...in the plane of the galaxy. 815 00:57:12,210 --> 00:57:14,201 But you don't need a spacecraft to see it. 816 00:57:14,412 --> 00:57:17,438 If it's a clear night, why not go out and take a look... 817 00:57:17,649 --> 00:57:19,276 ...at the Milky Way? 818 00:57:19,984 --> 00:57:22,145 There's also new evidence suggesting... 819 00:57:22,353 --> 00:57:26,084 ...that the Milky Way is not so much an ordinary spiral galaxy... 820 00:57:26,291 --> 00:57:29,192 ...as a barred spiral, like this. 821 00:57:33,565 --> 00:57:36,432 Important work has now been done on mapping... 822 00:57:36,634 --> 00:57:41,162 ...how the galaxies are scattered through intergalactic space. 823 00:57:41,506 --> 00:57:44,373 To the surprise of a lot of scientists... 824 00:57:44,576 --> 00:57:47,739 ...on a scale of hundreds of millions of light-years... 825 00:57:47,946 --> 00:57:52,349 ...the galaxies turn out not to be strewn at random... 826 00:57:52,550 --> 00:57:55,519 ...or concentrated in clusters of galaxies... 827 00:57:55,720 --> 00:57:57,847 ...but instead, strung out... 828 00:57:58,056 --> 00:58:02,459 ...along odd, irregular surfaces, like this. 829 00:58:03,695 --> 00:58:06,459 Every dot in this computer animation... 830 00:58:06,664 --> 00:58:08,154 ...is a galaxy. 831 00:58:08,499 --> 00:58:11,935 The computer lets us look at this distribution of galaxies... 832 00:58:12,136 --> 00:58:13,603 ...from many points of view... 833 00:58:13,805 --> 00:58:16,797 ...but this is how it looks from the Earth. 834 00:58:17,108 --> 00:58:21,442 There is an odd mannequin shape... 835 00:58:21,646 --> 00:58:25,514 ...that is presented by the distribution of galaxies. 836 00:58:25,717 --> 00:58:27,844 This work has been done... 837 00:58:28,052 --> 00:58:30,384 ...mainly by Margaret Geller... 838 00:58:30,588 --> 00:58:32,681 ...with her collaborator John Huchra... 839 00:58:32,891 --> 00:58:36,088 ...at Harvard University and the Smithsonian Institution. 840 00:58:45,570 --> 00:58:48,971 It's a little like soap bubbles in a bathtub... 841 00:58:49,173 --> 00:58:50,834 ...or dishwashing detergent. 842 00:58:51,042 --> 00:58:54,910 The galaxies are on the surfaces of the bubbles. 843 00:58:55,113 --> 00:58:59,049 The insides of the bubbles seem to have no galaxies in them at all. 844 00:58:59,250 --> 00:59:03,380 An average bubble is about 100 million light-years across. 845 00:59:03,588 --> 00:59:06,216 And that means that we've mapped still only... 846 00:59:06,424 --> 00:59:09,359 ...a very small volume of the accessible universe... 847 00:59:09,560 --> 00:59:11,460 ...the galaxies nearest to us. 848 00:59:11,663 --> 00:59:15,064 But pretty soon, we should be able to extend this search out... 849 00:59:15,266 --> 00:59:16,858 ...to enormous distances... 850 00:59:17,068 --> 00:59:19,468 ...so far away in space, that we're looking... 851 00:59:19,671 --> 00:59:23,266 ...back to the time that galaxies and their structures... 852 00:59:23,474 --> 00:59:24,702 ...were first formed. 853 00:59:25,109 --> 00:59:27,600 And this poses a real problem. 854 00:59:27,812 --> 00:59:30,474 Most cosmologists hold that the galaxies arise from... 855 00:59:30,682 --> 00:59:34,482 ...a preexisting lumpiness in the early universe... 856 00:59:34,686 --> 00:59:37,678 ...with the little lumps growing into galaxies. 857 00:59:37,889 --> 00:59:40,483 But the background radiation from the big bang... 858 00:59:40,692 --> 00:59:42,159 ...that fills all of space... 859 00:59:42,360 --> 00:59:44,954 ...has now been carefully measured... 860 00:59:45,163 --> 00:59:48,690 ...by that same Coby satellite that took that picture. 861 00:59:49,200 --> 00:59:52,795 Now, those radio waves seem almost perfectly uniform... 862 00:59:53,004 --> 00:59:54,301 ...across the sky... 863 00:59:54,505 --> 00:59:58,066 ...as if the big bang weren't lumpy or granular at all. 864 00:59:58,276 --> 01:00:01,370 But if early radiation and matter in the universe weren't lumpy... 865 01:00:01,579 --> 01:00:03,911 ...how could individual galaxies form? 866 01:00:04,115 --> 01:00:05,912 How could the bubbles form? 867 01:00:06,117 --> 01:00:07,641 Is there a contradiction... 868 01:00:07,852 --> 01:00:10,753 ...between the uniformity of the big bang radio waves... 869 01:00:10,955 --> 01:00:13,253 ...and the bubble structures formed by the galaxies? 870 01:00:13,458 --> 01:00:14,789 That's the question. 871 01:00:14,993 --> 01:00:18,929 When our survey of galaxies reaches out to billions of light-years... 872 01:00:19,130 --> 01:00:21,428 ...we'll have the answer to this question. 873 01:00:21,733 --> 01:00:24,099 Incidentally, maybe you're thinking... 874 01:00:24,302 --> 01:00:27,669 ...that the bubbles imply a bubble maker. 875 01:00:30,408 --> 01:00:32,308 But then I'd have to ask you: 876 01:00:32,510 --> 01:00:34,137 "Who made the bubble maker?" 877 01:00:34,345 --> 01:00:37,678 There's another infinite regress lurking here. 878 01:00:38,249 --> 01:00:40,308 And to one of the grandest questions... 879 01:00:40,518 --> 01:00:43,453 ...whether there's enough matter in the universe to close it... 880 01:00:43,654 --> 01:00:46,054 ...the only fair answer is that we don't know. 881 01:00:46,257 --> 01:00:47,622 If it is closed... 882 01:00:47,825 --> 01:00:49,793 ...what is the hidden matter that's closing it? 883 01:00:49,994 --> 01:00:53,623 Is it faint stars, black holes, massive neutrinos... 884 01:00:53,831 --> 01:00:57,562 ...some exotic kind of dark matter unknown on Earth? 885 01:00:57,769 --> 01:00:58,895 We don't know. 886 01:00:59,103 --> 01:01:03,199 But there are reasons to think that we'll soon find out the answers.