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