1 00:00:09,200 --> 00:00:11,399 Hello. My name is Ann Druyan. 2 00:00:11,400 --> 00:00:13,399 When Carl Sagan, Steven Soter and I... 3 00:00:13,400 --> 00:00:17,199 ...wrote the Cosmos TV series in the late 1970s... 4 00:00:17,200 --> 00:00:18,899 ...a lot of things where different. 5 00:00:18,900 --> 00:00:21,099 Back then, the U.S. and the Soviet Union... 6 00:00:21,100 --> 00:00:24,299 ...held the hole planet in their perpetual hostage crisis... 7 00:00:24,300 --> 00:00:26,199 ...called the Cold War. 8 00:00:26,200 --> 00:00:29,599 The wealth and scientific ingenuity of our civilization... 9 00:00:29,600 --> 00:00:32,299 ...was being squandered on a runaway arms raise. 10 00:00:32,300 --> 00:00:35,199 Then employed half the world scientists... 11 00:00:35,200 --> 00:00:39,200 ...and infested the world with 50.000 nuclear weapons. 12 00:00:41,100 --> 00:00:43,399 So much has happened since then. 13 00:00:43,400 --> 00:00:44,999 The Cold War is history... 14 00:00:45,000 --> 00:00:47,999 ...and science has made great strides. 15 00:00:48,000 --> 00:00:51,799 We've completed the spacecraft recognizance of the Solar System... 16 00:00:51,800 --> 00:00:55,799 ...the preliminary mapping of the visible universe that surrounds us... 17 00:00:55,800 --> 00:00:59,800 ...and we've charted the universe within: the human genome. 18 00:01:00,700 --> 00:01:04,599 When Cosmos was first broadcast there was no World Wide Web... 19 00:01:04,600 --> 00:01:06,799 ...it was a different world. 20 00:01:06,800 --> 00:01:08,899 What a tribute to Carl Sagan... 21 00:01:08,900 --> 00:01:12,599 ...a scientist who took many a punch for daring to speculate... 22 00:01:12,600 --> 00:01:16,600 ...that even after 20 of the most eventful years in the history of science... 23 00:01:17,400 --> 00:01:21,400 ...Cosmos requires few revisions and indeed is rich in prophecy. 24 00:01:24,000 --> 00:01:27,999 Cosmos is both the history of the scientific enterprise... 25 00:01:28,000 --> 00:01:32,000 ...and an attempt to convey the spiritual high... 26 00:01:32,100 --> 00:01:34,399 ...of its central revelation: 27 00:01:34,400 --> 00:01:37,299 Our oneness with the universe. 28 00:01:37,300 --> 00:01:41,299 Now, please, enjoy Cosmos, the proud saga of how... 29 00:01:41,300 --> 00:01:45,300 ...through the searching of 40.000 generations of our ancestors... 30 00:01:46,000 --> 00:01:48,399 ...we have come to discover our coordinates... 31 00:01:48,400 --> 00:01:51,299 ...in space and in time. 32 00:01:51,300 --> 00:01:55,300 And how, through the awesomely powerful method of science... 33 00:01:56,100 --> 00:02:00,100 ...we have been able to reconstruct the sweep of cosmic evolution... 34 00:02:00,700 --> 00:02:04,700 ...and defined our own part in its great story. 35 00:03:16,278 --> 00:03:19,111 The cosmos is all that is... 36 00:03:19,314 --> 00:03:22,442 ...or ever was or ever will be. 37 00:03:22,818 --> 00:03:26,276 Our contemplations of the cosmos stir us. 38 00:03:27,889 --> 00:03:31,586 There is a tingling in the spine, a catch in the voice... 39 00:03:31,793 --> 00:03:35,251 ...a faint sensation, as if a distant memory... 40 00:03:35,464 --> 00:03:37,830 ...of falling from a great height. 41 00:03:38,033 --> 00:03:42,163 We know we are approaching the grandest of mysteries. 42 00:03:46,875 --> 00:03:49,776 The size and age of the cosmos... 43 00:03:49,978 --> 00:03:52,446 ...are beyond ordinary human understanding. 44 00:03:52,647 --> 00:03:57,243 Lost somewhere between immensity and eternity... 45 00:03:57,452 --> 00:04:00,387 ...is our tiny planetary home, the Earth. 46 00:04:00,589 --> 00:04:03,820 For the first time, we have the power to decide... 47 00:04:04,025 --> 00:04:06,619 ...the fate of our planet and ourselves. 48 00:04:06,828 --> 00:04:08,659 This is a time of great danger. 49 00:04:08,864 --> 00:04:13,096 But our species is young and curious and brave. 50 00:04:13,301 --> 00:04:14,996 It shows much promise. 51 00:04:15,203 --> 00:04:17,330 In the last few millennia, we've made... 52 00:04:17,539 --> 00:04:20,406 ...the most astonishing and unexpected discoveries... 53 00:04:20,609 --> 00:04:23,840 ...about the cosmos and our place within it. 54 00:04:24,045 --> 00:04:26,843 I believe our future depends powerfully on... 55 00:04:27,048 --> 00:04:29,380 ...how well we understand this cosmos... 56 00:04:29,584 --> 00:04:32,712 ...in which we float like a mote of dust... 57 00:04:32,921 --> 00:04:34,752 ...in the morning sky. 58 00:04:39,928 --> 00:04:43,989 We're about to begin a journey through the cosmos. 59 00:04:44,866 --> 00:04:47,858 We'll encounter galaxies and suns and planets... 60 00:04:48,069 --> 00:04:50,003 ...life and consciousness... 61 00:04:50,205 --> 00:04:53,971 ...coming into being, evolving and perishing. 62 00:04:54,442 --> 00:04:57,900 Worlds of ice and stars of diamond. 63 00:04:58,113 --> 00:05:00,104 Atoms as massive as suns... 64 00:05:00,315 --> 00:05:03,307 ...and universes smaller than atoms. 65 00:05:03,685 --> 00:05:06,051 But it's also a story of our own planet... 66 00:05:06,254 --> 00:05:08,848 ...and the plants and animals that share it with us. 67 00:05:09,057 --> 00:05:12,117 And it's a story about us: 68 00:05:12,327 --> 00:05:15,728 How we achieved our present understanding of the cosmos... 69 00:05:15,931 --> 00:05:19,230 ...how the cosmos has shaped our evolution and our culture... 70 00:05:19,434 --> 00:05:21,026 ...and what our fate may be. 71 00:05:26,274 --> 00:05:29,607 We wish to pursue the truth, no matter where it leads. 72 00:05:29,811 --> 00:05:34,180 But to find the truth, we need imagination and skepticism both. 73 00:05:34,382 --> 00:05:36,646 We will not be afraid to speculate. 74 00:05:36,852 --> 00:05:41,289 But we will be careful to distinguish speculation from fact. 75 00:05:41,489 --> 00:05:46,119 The cosmos is full beyond measure of elegant truths... 76 00:05:46,328 --> 00:05:48,626 ...of exquisite interrelationships... 77 00:05:48,830 --> 00:05:51,822 ...of the awesome machinery of nature. 78 00:05:53,101 --> 00:05:57,663 The surface of the Earth is the shore of the cosmic ocean. 79 00:05:57,873 --> 00:06:01,240 On this shore, we have learned most of what we know. 80 00:06:01,443 --> 00:06:04,003 Recently, we've waded a little way out... 81 00:06:04,212 --> 00:06:08,478 ...maybe ankle-deep, and the water seems inviting. 82 00:06:08,917 --> 00:06:13,479 Some part of our being knows this is where we came from. 83 00:06:13,688 --> 00:06:16,122 We long to return. 84 00:06:16,491 --> 00:06:17,583 And we can. 85 00:06:17,792 --> 00:06:21,922 Because the cosmos is also within us. We're made of star-stuff. 86 00:06:22,130 --> 00:06:26,533 We are a way for the cosmos to know itself. 87 00:06:26,868 --> 00:06:29,462 The journey for each of us begins here. 88 00:06:29,871 --> 00:06:33,568 We're going to explore the cosmos in a ship of the imagination... 89 00:06:33,775 --> 00:06:38,007 ...unfettered by ordinary limits on speed and size... 90 00:06:38,213 --> 00:06:40,943 ...drawn by the music of cosmic harmonies... 91 00:06:41,149 --> 00:06:43,549 ...it can take us anywhere in space and time. 92 00:06:44,486 --> 00:06:46,545 Perfect as a snowflake... 93 00:06:46,955 --> 00:06:50,516 ...organic as a dandelion seed... 94 00:06:50,725 --> 00:06:51,885 ...it will carry us... 95 00:06:52,093 --> 00:06:55,961 ...to worlds of dreams and worlds of facts. 96 00:06:56,932 --> 00:06:57,956 Come with me. 97 00:07:09,077 --> 00:07:13,980 Before us is the cosmos on the grandest scale we know. 98 00:07:19,387 --> 00:07:21,821 We are far from the shores of Earth... 99 00:07:22,023 --> 00:07:25,151 ...in the uncharted reaches of the cosmic ocean. 100 00:07:25,360 --> 00:07:28,852 Strewn like sea froth on the waves of space... 101 00:07:29,064 --> 00:07:31,794 ...are innumerable faint tendrils of light. 102 00:07:32,000 --> 00:07:34,366 Some of them containing hundreds... 103 00:07:34,569 --> 00:07:37,766 ...of billions of suns. 104 00:07:37,973 --> 00:07:40,635 These are the galaxies... 105 00:07:40,842 --> 00:07:44,869 ...drifting endlessly in the great cosmic dark. 106 00:07:47,582 --> 00:07:49,573 In our ship of the imagination... 107 00:07:49,784 --> 00:07:53,845 ...we are halfway to the edge of the known universe. 108 00:08:03,198 --> 00:08:06,656 In this, the first of our cosmic voyages... 109 00:08:06,901 --> 00:08:11,497 ...we begin to explore the universe revealed by science. 110 00:08:18,413 --> 00:08:23,316 Our course will eventually carry us to a far-off and exotic world. 111 00:08:23,518 --> 00:08:26,510 But from the depths of space, we cannot detect even... 112 00:08:26,721 --> 00:08:29,952 ...the cluster of galaxies in which our Milky Way is embedded... 113 00:08:30,158 --> 00:08:32,991 ...much less the sun or the Earth. 114 00:08:49,377 --> 00:08:51,811 We are in the realm of the galaxies... 115 00:08:52,013 --> 00:08:55,449 ...8 billion light years from home. 116 00:09:00,221 --> 00:09:04,851 No matter where we travel, the patterns of nature are the same... 117 00:09:05,060 --> 00:09:08,552 ...as in the form of this spiral galaxy. 118 00:09:10,665 --> 00:09:13,498 The same laws of physics apply everywhere... 119 00:09:13,701 --> 00:09:15,828 ...throughout the cosmos. 120 00:09:21,076 --> 00:09:24,170 But we have just begun to understand these laws. 121 00:09:24,379 --> 00:09:28,475 The universe is rich in mystery. 122 00:09:33,121 --> 00:09:35,681 Near the center of a cluster of galaxies... 123 00:09:35,890 --> 00:09:39,690 ...there's sometimes a rogue, elliptical galaxy... 124 00:09:39,894 --> 00:09:41,953 ...made of a trillion suns... 125 00:09:42,163 --> 00:09:44,358 ...which devours its neighbors. 126 00:09:44,566 --> 00:09:46,796 Perhaps this cyclone of stars... 127 00:09:47,001 --> 00:09:50,129 ...is what astronomers on Earth call a quasar. 128 00:10:06,087 --> 00:10:09,488 Our ordinary measures of distance fail us... 129 00:10:09,691 --> 00:10:12,455 ...here in the realm of the galaxies. 130 00:10:12,660 --> 00:10:15,254 We need a much larger unit: the light year. 131 00:10:15,463 --> 00:10:18,023 It measures how far light travels in a year... 132 00:10:18,233 --> 00:10:21,134 ...nearly 10 trillion kilometers. 133 00:10:21,336 --> 00:10:25,898 It measures not time, but enormous distances. 134 00:10:39,654 --> 00:10:41,383 In the Hercules cluster... 135 00:10:41,589 --> 00:10:46,049 ...the individual galaxies are about 300,000 light years apart. 136 00:10:46,261 --> 00:10:49,992 So light takes about 300,000 years... 137 00:10:50,198 --> 00:10:53,395 ...to go from one galaxy to another. 138 00:10:56,704 --> 00:11:00,265 Like stars and planets and people... 139 00:11:00,475 --> 00:11:04,639 ...galaxies are born, live and die. 140 00:11:05,146 --> 00:11:09,139 They may all experience a tumultuous adolescence. 141 00:11:09,350 --> 00:11:13,480 During their first 100 million years, their cores may explode. 142 00:11:13,688 --> 00:11:16,623 Seen in radio light, great jets of energy... 143 00:11:16,824 --> 00:11:19,952 ...pour out and echo across the cosmos. 144 00:11:21,062 --> 00:11:25,499 Worlds near the core or along the jets would be incinerated. 145 00:11:26,301 --> 00:11:30,260 I wonder how many planets and how many civilizations... 146 00:11:30,471 --> 00:11:32,336 ...might be destroyed. 147 00:11:40,415 --> 00:11:44,249 In the Pegasus cluster, there's a ring galaxy... 148 00:11:44,452 --> 00:11:47,615 ...the wreckage left from the collision of two galaxies. 149 00:11:47,822 --> 00:11:51,383 A splash in the cosmic pond. 150 00:11:51,859 --> 00:11:55,295 Individual galaxies may explode and collide... 151 00:11:55,496 --> 00:11:58,988 ...and their constituent stars may blow up as well. 152 00:11:59,834 --> 00:12:02,200 In this supernova explosion... 153 00:12:02,403 --> 00:12:06,533 ...a single star outshines the rest of its galaxy. 154 00:12:09,277 --> 00:12:12,735 We are approaching what astronomers on Earth call... 155 00:12:12,947 --> 00:12:15,177 ...the Local Group. 156 00:12:16,951 --> 00:12:21,888 Three million light years across, it contains some 20 galaxies. 157 00:12:22,924 --> 00:12:26,553 It's a sparse and rather typical chain of islands... 158 00:12:26,761 --> 00:12:29,559 ...in the immense cosmic ocean. 159 00:12:30,598 --> 00:12:34,728 We are now only 2 million light years from home. 160 00:12:35,803 --> 00:12:39,239 On the maps of space, this galaxy is called M31... 161 00:12:39,440 --> 00:12:41,635 ...the great galaxy Andromeda. 162 00:12:41,843 --> 00:12:45,438 It's a vast storm of stars and gas and dust. 163 00:12:45,647 --> 00:12:46,944 As we pass over it... 164 00:12:47,148 --> 00:12:50,811 ...we see one of its small satellite galaxies. 165 00:12:54,656 --> 00:12:56,283 Clusters of galaxies... 166 00:12:56,491 --> 00:12:59,051 ...and the stars of individual galaxies... 167 00:12:59,260 --> 00:13:01,990 ...are all held together by gravity. 168 00:13:02,196 --> 00:13:03,925 Surrounding M31... 169 00:13:04,132 --> 00:13:07,863 ...are hundreds of globular star clusters. 170 00:13:08,870 --> 00:13:11,065 We're approaching one of them. 171 00:13:11,472 --> 00:13:15,067 Each cluster orbits the massive center of the galaxy. 172 00:13:15,276 --> 00:13:19,474 Some contain up to a million separate stars. 173 00:13:19,914 --> 00:13:23,475 Every globular cluster is like a swarm of bees... 174 00:13:23,685 --> 00:13:25,084 ...bound by gravity... 175 00:13:25,286 --> 00:13:27,516 ...every bee, a sun. 176 00:13:30,658 --> 00:13:33,149 From Pegasus, our voyage has taken us... 177 00:13:33,361 --> 00:13:36,888 ...200 million light years to the Local Group... 178 00:13:37,098 --> 00:13:41,364 ...dominated by two great spiral galaxies. 179 00:13:42,537 --> 00:13:46,371 Beyond M31 is another very similar galaxy. 180 00:13:46,574 --> 00:13:49,008 Its spiral arms slowly turning... 181 00:13:49,210 --> 00:13:51,974 ...once every quarter billion years. 182 00:13:58,286 --> 00:14:01,084 This is our own Milky Way... 183 00:14:01,289 --> 00:14:04,156 ...seen from the outside. 184 00:14:10,431 --> 00:14:15,061 This is the home galaxy of the human species. 185 00:14:22,577 --> 00:14:27,514 In the obscure backwaters of the Carina-Cygnus spiral arm... 186 00:14:27,782 --> 00:14:31,047 ...we humans have evolved to consciousness... 187 00:14:31,252 --> 00:14:34,087 ...and some measure of understanding. 188 00:14:34,088 --> 00:14:37,421 This region of the Milky Way galaxy is now usually called the Local Arm... 189 00:14:37,625 --> 00:14:41,356 ...or the Orion Arm, but the spiral arm nomenclature remains rather fuzzy. 190 00:14:42,630 --> 00:14:45,360 Concentrated in its brilliant core... 191 00:14:45,566 --> 00:14:48,296 ...and strewn along its spiral arms... 192 00:14:48,503 --> 00:14:52,530 ...are 400 billion suns. 193 00:14:54,909 --> 00:14:57,400 It takes light 100,000 years to travel... 194 00:14:57,612 --> 00:15:00,581 ...from one end of the galaxy to the other. 195 00:15:02,617 --> 00:15:06,576 Within this galaxy are stars and worlds... 196 00:15:06,788 --> 00:15:11,122 ...and, it may be, an enormous diversity of living things... 197 00:15:11,325 --> 00:15:16,262 ...and intelligent beings and space faring civilizations. 198 00:15:24,172 --> 00:15:26,970 Scattered among the stars of the Milky Way... 199 00:15:27,175 --> 00:15:29,143 ...are supernova remnants... 200 00:15:29,343 --> 00:15:33,609 ...each one the remains of a colossal stellar explosion. 201 00:15:33,881 --> 00:15:35,906 These filaments of glowing gas... 202 00:15:36,117 --> 00:15:40,144 ...are the outer layers of a star which has recently destroyed itself. 203 00:15:40,354 --> 00:15:42,083 The gas is unraveling... 204 00:15:42,290 --> 00:15:45,817 ...returning star-stuff back into space. 205 00:15:50,031 --> 00:15:53,296 And at its heart, are the remains of the original star... 206 00:15:53,501 --> 00:15:58,165 ...a dense, shrunken stellar fragment called a pulsar. 207 00:15:58,372 --> 00:16:01,671 A natural lighthouse, blinking and hissing. 208 00:16:01,909 --> 00:16:05,401 A sun that spins twice each second. 209 00:16:11,252 --> 00:16:14,619 Pulsars keep such perfect time that the first one discovered... 210 00:16:14,822 --> 00:16:17,723 ...was thought to be a sign of extraterrestrial intelligence. 211 00:16:17,925 --> 00:16:20,291 Perhaps a navigational beacon... 212 00:16:20,495 --> 00:16:23,430 ...for great ships that travel across the light years... 213 00:16:23,764 --> 00:16:25,789 ...and between the stars. 214 00:16:29,437 --> 00:16:33,032 There may be such intelligences and such starships... 215 00:16:33,241 --> 00:16:37,007 ...but pulsars are not their signature. 216 00:16:47,188 --> 00:16:50,589 Instead, they are the doleful reminders... 217 00:16:50,791 --> 00:16:52,554 ...that nothing lasts forever... 218 00:16:52,760 --> 00:16:55,456 ...that stars also die. 219 00:16:58,099 --> 00:17:02,035 We continue to plummet, falling thousands of light years... 220 00:17:02,236 --> 00:17:04,761 ...towards the plane of the galaxy. 221 00:17:07,108 --> 00:17:08,735 This is the Milky Way... 222 00:17:08,943 --> 00:17:11,411 ...our galaxy seen edge on. 223 00:17:11,612 --> 00:17:13,705 Billions of nuclear furnaces... 224 00:17:13,915 --> 00:17:16,975 ...converting matter into starlight. 225 00:17:21,889 --> 00:17:24,790 Some stars are flimsy as a soap bubble. 226 00:17:24,992 --> 00:17:29,361 Others are 100 trillion times denser than lead. 227 00:17:29,564 --> 00:17:33,091 The hottest stars are destined to die young. 228 00:17:33,534 --> 00:17:36,799 But red giants are mostly elderly. 229 00:17:37,004 --> 00:17:41,100 Such stars are unlikely to have inhabited planets. 230 00:17:43,978 --> 00:17:46,674 But yellow dwarf stars, like the sun... 231 00:17:46,881 --> 00:17:50,749 ...are middle-aged and they are far more common. 232 00:17:51,452 --> 00:17:54,387 These stars may have planetary systems. 233 00:17:54,589 --> 00:17:58,184 And on such planets, for the first time on our cosmic voyage... 234 00:17:58,392 --> 00:18:00,883 ...we encounter rare forms of matter: 235 00:18:01,095 --> 00:18:05,691 Ice and rock, air and liquid water. 236 00:18:10,638 --> 00:18:12,265 Close to this yellow star... 237 00:18:12,506 --> 00:18:15,498 ...is a small, warm, cloudy world... 238 00:18:15,710 --> 00:18:17,871 ...with continents and oceans. 239 00:18:18,079 --> 00:18:23,016 These conditions permit an even more precious form of matter to arise: 240 00:18:23,417 --> 00:18:24,714 Life. 241 00:18:31,926 --> 00:18:33,791 But this is not the Earth. 242 00:18:33,995 --> 00:18:38,659 Intelligent beings have evolved and reworked this planetary surface... 243 00:18:38,866 --> 00:18:41,733 ...in a massive engineering enterprise. 244 00:18:41,936 --> 00:18:45,167 In the Milky Way galaxy, there may be many worlds... 245 00:18:45,373 --> 00:18:48,809 ...on which matter has grown to consciousness. 246 00:18:56,083 --> 00:18:59,416 I wonder, are they very different from us? 247 00:18:59,620 --> 00:19:01,053 What do they look like? 248 00:19:01,255 --> 00:19:05,351 What are their politics, technology, music, religion? 249 00:19:05,860 --> 00:19:10,354 Or do they have patterns of culture we can't begin to imagine? 250 00:19:10,564 --> 00:19:14,796 Are they also a danger to themselves? 251 00:19:21,709 --> 00:19:25,236 Among the many glowing clouds of interstellar gas... 252 00:19:25,446 --> 00:19:28,438 ...is one called the Orion Nebula... 253 00:19:28,683 --> 00:19:31,811 ...only 1500 light years from Earth. 254 00:19:37,224 --> 00:19:40,625 These three bright stars are seen by earthlings... 255 00:19:40,828 --> 00:19:45,629 ...as the belt in the familiar constellation of Orion the hunter. 256 00:19:52,039 --> 00:19:55,202 The nebula appears from Earth as a patch of light... 257 00:19:55,409 --> 00:19:59,641 ...the middle star in Orion's sword. 258 00:20:07,621 --> 00:20:10,089 But it is not a star. 259 00:20:10,291 --> 00:20:13,226 It is another thing entirely. 260 00:20:13,427 --> 00:20:18,194 A cloud that veils one of nature's secret places. 261 00:20:27,241 --> 00:20:32,178 This is a stellar nursery, a place where stars are born. 262 00:20:32,413 --> 00:20:35,177 They condense by gravity from gas and dust... 263 00:20:35,382 --> 00:20:40,217 ...until their temperatures become so high that they begin to shine. 264 00:20:40,755 --> 00:20:43,485 Such clouds mark the births of stars... 265 00:20:43,691 --> 00:20:46,524 ...as others bear witness to their deaths. 266 00:20:52,633 --> 00:20:56,865 After stars condense in the hidden interiors of interstellar clouds... 267 00:20:57,071 --> 00:20:58,561 ...what happens to them? 268 00:20:58,773 --> 00:21:02,300 The Pleiades are a loose cluster of young stars... 269 00:21:02,510 --> 00:21:04,569 ...only 50 million years old. 270 00:21:04,779 --> 00:21:09,716 These fledgling stars are just being let out into the galaxy. 271 00:21:09,950 --> 00:21:13,147 Still surrounded by wisps of nebulosity... 272 00:21:13,354 --> 00:21:16,881 ...the gas and dust from which they formed. 273 00:21:51,292 --> 00:21:54,659 There are clouds that hang like inkblots... 274 00:21:54,862 --> 00:21:56,489 ...between the stars. 275 00:21:56,697 --> 00:21:59,495 They are made of fine, rocky dust... 276 00:21:59,700 --> 00:22:02,100 ...organic matter and ice. 277 00:22:03,804 --> 00:22:07,797 Inside, a few stars begin to turn on. 278 00:22:08,008 --> 00:22:09,908 Nearby worlds of ice evaporate... 279 00:22:10,110 --> 00:22:12,704 ...and form long, comet-like tails... 280 00:22:12,913 --> 00:22:15,848 ...driven back by the stellar winds. 281 00:22:20,788 --> 00:22:24,053 Black clouds, light years across... 282 00:22:24,258 --> 00:22:26,226 ...drift between the stars. 283 00:22:26,427 --> 00:22:29,362 They're filled with organic molecules. 284 00:22:29,563 --> 00:22:32,430 The building blocks of life are everywhere. 285 00:22:32,633 --> 00:22:34,601 They are easily made. 286 00:22:34,802 --> 00:22:39,739 On how many worlds have such complex molecules assembled themselves... 287 00:22:40,007 --> 00:22:43,670 ...into patterns we would call alive? 288 00:22:49,016 --> 00:22:53,885 Most stars belong to systems of two or three or many suns... 289 00:22:54,088 --> 00:22:56,079 ...bound together by gravity. 290 00:22:56,290 --> 00:22:59,521 Each system is isolated from its neighbors... 291 00:22:59,727 --> 00:23:01,285 ...by the light years. 292 00:23:03,597 --> 00:23:07,397 We are approaching a single, ordinary, yellow dwarf star... 293 00:23:07,601 --> 00:23:10,297 ...surrounded by a system of nine planets... 294 00:23:10,504 --> 00:23:14,964 ...dozens of moons, thousands of asteroids and billions of comets: 295 00:23:15,209 --> 00:23:17,234 The family of the sun. 296 00:23:18,979 --> 00:23:23,245 Only four light hours from Earth is the planet Neptune... 297 00:23:23,450 --> 00:23:26,214 ...and its giant satellite, Triton. 298 00:23:29,957 --> 00:23:32,824 Even in the outskirts of our own solar system... 299 00:23:33,027 --> 00:23:37,123 ...we humans have barely begun our explorations. 300 00:23:39,566 --> 00:23:40,965 Only a century ago... 301 00:23:41,168 --> 00:23:45,036 ...we were ignorant even of the existence of the planet Pluto. 302 00:23:45,239 --> 00:23:47,573 Its moon, Charon, remained undiscovered until 1978. 303 00:23:47,574 --> 00:23:52,238 Since the discovery of Kuiper Belt objects in 1992, Pluto has come to be seen... 304 00:23:52,446 --> 00:23:55,148 ...as the largest member of this population of comets. 305 00:23:55,149 --> 00:23:55,516 The rings of Uranus were first detected in 1977. 306 00:23:55,517 --> 00:23:58,542 Many astronomers no longer regard it as a planet. 307 00:23:59,820 --> 00:24:03,688 There are new worlds to chart even this close to home. 308 00:24:07,127 --> 00:24:10,460 Saturn is a giant gas world. 309 00:24:10,664 --> 00:24:12,632 If it has a solid surface... 310 00:24:12,833 --> 00:24:16,633 ...it must lie far below the clouds we see. 311 00:24:18,272 --> 00:24:20,206 Saturn's majestic rings... 312 00:24:20,407 --> 00:24:23,672 ...are made of trillions of orbiting snowballs. 313 00:24:29,550 --> 00:24:33,577 We are now only 80 light minutes from home. 314 00:24:33,787 --> 00:24:37,279 A mere 1 1/2 billion kilometers. 315 00:24:51,105 --> 00:24:54,973 The largest planet in our solar system is Jupiter. 316 00:24:55,175 --> 00:24:59,509 On its dark side, super bolts of lightning illuminate the clouds... 317 00:24:59,713 --> 00:25:04,548 ...as first revealed by the Voyager spacecraft in 1979. 318 00:25:16,764 --> 00:25:18,595 Inside the orbit of Jupiter... 319 00:25:18,799 --> 00:25:22,394 ...are countless shattered and broken world-lets: 320 00:25:22,603 --> 00:25:24,195 The asteroids. 321 00:25:24,405 --> 00:25:26,498 These reefs and shoals... 322 00:25:26,707 --> 00:25:29,870 ...mark the border of the realm of giant planets. 323 00:25:30,077 --> 00:25:34,480 We are now entering the shallows of the solar system. 324 00:25:36,216 --> 00:25:40,550 Here there are worlds with thin atmospheres and solid surfaces: 325 00:25:40,754 --> 00:25:42,085 Earth-like planets... 326 00:25:42,289 --> 00:25:46,316 ...with landscapes crying out for careful exploration. 327 00:25:46,527 --> 00:25:49,519 This world is Mars. 328 00:25:51,999 --> 00:25:55,491 In 1976, after a year's voyage... 329 00:25:55,702 --> 00:25:58,193 ...two robot explorers from Earth... 330 00:25:58,405 --> 00:26:00,999 ...landed on this alien shore. 331 00:26:02,876 --> 00:26:06,471 On Mars, there is a volcano as wide as Arizona... 332 00:26:06,680 --> 00:26:09,444 ...and almost three times the height of Mount Everest. 333 00:26:09,650 --> 00:26:12,778 We've named it Mount Olympus. 334 00:26:17,491 --> 00:26:20,426 This is a world of wonders. 335 00:26:22,096 --> 00:26:24,724 Mars is a planet with ancient river valleys... 336 00:26:24,932 --> 00:26:29,869 ...and violent sandstorms driven by winds at half the speed of sound. 337 00:26:37,077 --> 00:26:41,912 There is a giant rift in its surface 5000 kilometers long. 338 00:26:42,116 --> 00:26:45,574 It's called Vallis Marinaris. 339 00:26:45,786 --> 00:26:48,118 The valley of the Mariner spacecraft... 340 00:26:48,322 --> 00:26:52,691 ...that came to explore Mars from a nearby world. 341 00:27:10,744 --> 00:27:14,009 In this, our first cosmic voyage... 342 00:27:14,214 --> 00:27:17,047 ...we have just begun the reconnaissance of Mars... 343 00:27:17,251 --> 00:27:20,709 ...and all those other planets and stars and galaxies. 344 00:27:20,921 --> 00:27:25,187 In voyages to come, we will explore them more fully. 345 00:27:32,733 --> 00:27:36,396 But now, we travel the few remaining light minutes... 346 00:27:36,603 --> 00:27:41,336 ...to a blue and cloudy world, third from the sun. 347 00:27:41,742 --> 00:27:43,801 The end of our long journey... 348 00:27:44,011 --> 00:27:46,411 ...is the world where we began. 349 00:27:46,747 --> 00:27:48,578 Our travels allow us... 350 00:27:48,782 --> 00:27:51,046 ...to see the Earth anew... 351 00:27:51,251 --> 00:27:54,311 ...as if we came from somewhere else. 352 00:27:56,757 --> 00:27:59,385 There are a hundred billion galaxies... 353 00:27:59,593 --> 00:28:02,585 ...and a billion trillion stars. 354 00:28:02,796 --> 00:28:07,392 Why should this modest planet be the only inhabited world? 355 00:28:07,601 --> 00:28:12,197 To me, it seems far more likely that the cosmos is brimming over... 356 00:28:12,406 --> 00:28:14,533 ...with life and intelligence. 357 00:28:14,741 --> 00:28:17,403 But so far, every living thing... 358 00:28:17,611 --> 00:28:19,203 ...every conscious being... 359 00:28:19,413 --> 00:28:22,109 ...every civilization we know anything about... 360 00:28:22,316 --> 00:28:25,012 ...lived there, on Earth. 361 00:28:32,259 --> 00:28:33,886 Beneath these clouds... 362 00:28:34,094 --> 00:28:37,723 ...the drama of the human species has been unfolded. 363 00:28:40,367 --> 00:28:43,598 We have, at last, come home. 364 00:28:53,313 --> 00:28:55,508 Welcome to the planet Earth. 365 00:28:55,849 --> 00:28:58,682 A place with blue nitrogen skies... 366 00:28:58,885 --> 00:29:00,785 ...oceans of liquid water... 367 00:29:00,988 --> 00:29:02,319 ...cool forests... 368 00:29:02,522 --> 00:29:03,921 ...soft meadows. 369 00:29:04,124 --> 00:29:07,753 A world positively rippling with life. 370 00:29:08,295 --> 00:29:11,822 In the cosmic perspective, it is, for the moment, unique. 371 00:29:12,032 --> 00:29:14,660 The only world in which we know with certainty... 372 00:29:14,868 --> 00:29:18,861 ...that the matter of the cosmos has become alive and aware. 373 00:29:19,106 --> 00:29:21,939 There must be many such worlds scattered through space... 374 00:29:22,142 --> 00:29:24,576 ...but our search for them begins here... 375 00:29:24,778 --> 00:29:28,179 ...with the accumulated wisdom of the men and women of our species... 376 00:29:28,382 --> 00:29:30,179 ...acquired at great cost... 377 00:29:30,384 --> 00:29:32,511 ...over a million years. 378 00:30:15,662 --> 00:30:18,563 There was once a time when our planet seemed immense. 379 00:30:18,765 --> 00:30:21,256 When it was the only world we could explore. 380 00:30:21,468 --> 00:30:25,700 Its true size was first worked out in a simple and ingenious way... 381 00:30:25,906 --> 00:30:30,172 ...by a man who lived here in Egypt, in the third century B.C. 382 00:30:36,116 --> 00:30:40,382 This tower may have been a communications tower. 383 00:30:40,587 --> 00:30:44,353 Part of a network running along the North African coast... 384 00:30:44,558 --> 00:30:48,961 ...by which signal bonfires were used to communicate messages of state. 385 00:30:49,162 --> 00:30:53,565 It also may have been used as a lighthouse... 386 00:30:53,767 --> 00:30:57,032 ...a navigational beacon for sailing ships... 387 00:30:57,237 --> 00:30:59,569 ...out there in the Mediterranean Sea. 388 00:30:59,773 --> 00:31:02,298 It is about 50 kilometers west... 389 00:31:02,509 --> 00:31:07,173 ...of what was once one of the great cities of the world, Alexandria. 390 00:31:08,115 --> 00:31:10,140 In Alexandria, at that time... 391 00:31:10,350 --> 00:31:13,376 ...there lived a man named Eratosthenes. 392 00:31:13,587 --> 00:31:18,081 A competitor called him "beta," the second letter of the Greek alphabet... 393 00:31:18,291 --> 00:31:22,990 ...because, he said, "Eratosthenes was second best in everything." 394 00:31:23,196 --> 00:31:27,929 But it seems clear, in many fields, Eratosthenes was "alpha." 395 00:31:28,135 --> 00:31:31,798 He was an astronomer, historian, geographer... 396 00:31:32,038 --> 00:31:35,906 ...philosopher, poet, theater critic and mathematician. 397 00:31:36,109 --> 00:31:40,512 He was also the chief librarian of the Great Library of Alexandria. 398 00:31:40,714 --> 00:31:45,651 And one day while reading a papyrus book in the library... 399 00:31:45,852 --> 00:31:49,788 ...he came upon a curious account. 400 00:31:57,030 --> 00:31:58,861 Far to the south, he read... 401 00:31:59,065 --> 00:32:01,397 ...at the frontier outpost of Syene... 402 00:32:01,601 --> 00:32:05,093 ...something notable could be seen on the longest day of the year. 403 00:32:10,076 --> 00:32:11,600 On June 21st... 404 00:32:11,812 --> 00:32:14,872 ...the shadows of a temple column, or a vertical stick... 405 00:32:15,081 --> 00:32:17,675 ...would grow shorter as noon approached. 406 00:32:23,623 --> 00:32:25,250 As the hours crept towards midday... 407 00:32:25,459 --> 00:32:29,691 ...the sun's rays would slither down the sides of a deep well... 408 00:32:29,896 --> 00:32:32,387 ...which on other days would remain in shadow. 409 00:32:39,339 --> 00:32:41,967 And then, precisely at noon... 410 00:32:42,175 --> 00:32:44,575 ...columns would cast no shadows. 411 00:32:44,778 --> 00:32:49,306 And the sun would shine directly down into the water of the well. 412 00:32:55,455 --> 00:32:56,888 At that moment... 413 00:32:57,090 --> 00:32:59,615 ...the sun was exactly overhead. 414 00:33:04,831 --> 00:33:09,165 It was an observation that someone else might easily have ignored. 415 00:33:09,369 --> 00:33:13,237 Sticks, shadows, reflections in wells... 416 00:33:13,440 --> 00:33:15,169 ...the position of the sun... 417 00:33:15,375 --> 00:33:17,400 ...simple, everyday matters. 418 00:33:17,611 --> 00:33:20,671 Of what possible importance might they be? 419 00:33:21,047 --> 00:33:23,743 But Eratosthenes was a scientist... 420 00:33:23,950 --> 00:33:27,408 ...and his contemplation of these homely matters changed the world... 421 00:33:27,621 --> 00:33:29,885 ...in a way, made the world. 422 00:33:30,090 --> 00:33:34,220 Because Eratosthenes had the presence of mind to experiment... 423 00:33:34,427 --> 00:33:38,887 ...to actually ask whether back here, near Alexandria... 424 00:33:39,099 --> 00:33:44,036 ...a stick cast a shadow near noon on June the 21 st. 425 00:33:44,404 --> 00:33:47,202 And it turns out, sticks do. 426 00:33:49,476 --> 00:33:51,910 An overly skeptical person might have said... 427 00:33:52,112 --> 00:33:54,774 ...that the report from Syene was an error. 428 00:33:54,981 --> 00:33:57,779 But it's an absolutely straightforward observation. 429 00:33:57,984 --> 00:34:01,147 Why would anyone lie on such a trivial matter? 430 00:34:01,354 --> 00:34:04,084 Eratosthenes asked himself how it could be... 431 00:34:04,291 --> 00:34:06,316 ...that at the same moment... 432 00:34:06,526 --> 00:34:09,188 ...a stick in Syene would cast no shadow... 433 00:34:09,396 --> 00:34:12,957 ...and a stick in Alexandria, 800 kilometers to the north... 434 00:34:13,166 --> 00:34:15,726 ...would cast a very definite shadow. 435 00:34:18,805 --> 00:34:22,070 Here is a map of ancient Egypt. 436 00:34:22,909 --> 00:34:26,276 I've inserted two sticks, or obelisks. 437 00:34:26,479 --> 00:34:30,939 One up here in Alexandria and one down here in Syene. 438 00:34:31,151 --> 00:34:34,985 Now, if at a certain moment each stick casts... 439 00:34:35,188 --> 00:34:37,588 ...no shadow, no shadow at all... 440 00:34:37,958 --> 00:34:42,224 ...that's perfectly easy to understand, provided the Earth is flat. 441 00:34:42,429 --> 00:34:45,626 If the shadow at Syene is at a certain length... 442 00:34:45,832 --> 00:34:48,266 ...and the shadow at Alexandria is the same length... 443 00:34:48,468 --> 00:34:51,028 ...that also makes sense on a flat Earth. 444 00:34:51,504 --> 00:34:54,735 But how could it be, Eratosthenes asked... 445 00:34:54,941 --> 00:34:59,435 ...that at the same instant there was no shadow at Syene... 446 00:34:59,779 --> 00:35:04,443 ...and a very substantial shadow at Alexandria? 447 00:35:05,785 --> 00:35:10,347 The only answer was that the surface of the Earth is curved. 448 00:35:10,590 --> 00:35:11,921 Not only that... 449 00:35:12,125 --> 00:35:15,925 ...but the greater the curvature, the bigger the difference... 450 00:35:16,129 --> 00:35:19,826 ...in the lengths of the shadows. The sun is so far away... 451 00:35:20,033 --> 00:35:22,467 ...that its rays are parallel when they reach the Earth. 452 00:35:22,669 --> 00:35:26,935 Sticks at different angles to the sun will cast shadows at different lengths. 453 00:35:27,140 --> 00:35:30,576 For the observed difference in the shadow lengths... 454 00:35:30,777 --> 00:35:33,211 ...the distance between Alexandria and Syene... 455 00:35:33,413 --> 00:35:37,315 ...had to be about seven degrees along the surface of the Earth. 456 00:35:37,517 --> 00:35:41,419 By that, I mean, if you would imagine these sticks extending... 457 00:35:41,621 --> 00:35:44,055 ...all the way down to the center of the Earth... 458 00:35:44,324 --> 00:35:47,418 ...they would there intersect at an angle of seven degrees. 459 00:35:47,627 --> 00:35:50,790 Well, seven degrees is something like a 50th... 460 00:35:50,997 --> 00:35:54,558 ...of the full circumference of the Earth, 360 degrees. 461 00:35:54,768 --> 00:35:59,296 Eratosthenes knew the distance between Alexandria and Syene. 462 00:35:59,506 --> 00:36:01,474 He knew it was 800 kilometers. 463 00:36:01,675 --> 00:36:06,271 Why? Because he hired a man to pace out the entire distance... 464 00:36:06,479 --> 00:36:09,937 ...so that he could perform the calculation I'm talking about. 465 00:36:10,150 --> 00:36:14,883 Now, 800 kilometers times 50 is 40,000 kilometers. 466 00:36:15,088 --> 00:36:17,181 That must be the circumference of the Earth. 467 00:36:17,390 --> 00:36:20,587 That's how far it is to go once around the Earth. 468 00:36:21,061 --> 00:36:22,528 That's the right answer. 469 00:36:22,729 --> 00:36:25,061 Eratosthenes' only tools were... 470 00:36:25,265 --> 00:36:29,133 ...sticks, eyes, feet and brains. 471 00:36:29,669 --> 00:36:32,695 Plus a zest for experiment. 472 00:36:33,406 --> 00:36:37,137 With those tools, he correctly deduced the circumference of the Earth... 473 00:36:37,343 --> 00:36:41,803 ...to high precision with an error of only a few percent. 474 00:36:42,916 --> 00:36:47,853 That's pretty good figuring for 2200 years ago. 475 00:36:58,198 --> 00:37:01,929 Then, as now, the Mediterranean was teeming with ships. 476 00:37:02,135 --> 00:37:06,231 Merchantmen, fishing vessels, naval flotillas. 477 00:37:06,439 --> 00:37:10,808 But there were also courageous voyages into the unknown. 478 00:37:12,212 --> 00:37:16,842 400 years before Eratosthenes, Africa was circumnavigated... 479 00:37:17,050 --> 00:37:19,985 ...by a Phoenician fleet in the employ... 480 00:37:20,186 --> 00:37:22,245 ...of the Egyptian pharaoh Necho. 481 00:37:22,455 --> 00:37:23,649 They set sail... 482 00:37:23,857 --> 00:37:28,385 ...probably in boats as frail and open as these... 483 00:37:28,595 --> 00:37:31,792 ...out from the Red Sea, down the east coast of Africa... 484 00:37:31,998 --> 00:37:35,263 ...up into the Atlantic and then back through the Mediterranean. 485 00:37:35,668 --> 00:37:38,364 That epic journey took three years... 486 00:37:38,571 --> 00:37:40,698 ...about as long as it takes Voyager... 487 00:37:40,907 --> 00:37:43,899 ...to journey from Earth to Saturn. 488 00:37:44,477 --> 00:37:47,105 After Eratosthenes, some may have attempted... 489 00:37:47,313 --> 00:37:49,679 ...to circumnavigate the Earth. 490 00:37:49,883 --> 00:37:52,784 But until the time of Magellan, no one succeeded. 491 00:37:53,386 --> 00:37:56,378 What tales of adventure and daring... 492 00:37:56,589 --> 00:37:58,716 ...must earlier have been told... 493 00:37:58,925 --> 00:38:03,259 ...as sailors and navigators, practical men of the world... 494 00:38:03,463 --> 00:38:06,330 ...gambled their lives on the mathematics... 495 00:38:06,533 --> 00:38:09,969 ...of a scientist from ancient Alexandria. 496 00:38:16,576 --> 00:38:20,239 Today, Alexandria shows few traces of its ancient glory... 497 00:38:20,446 --> 00:38:23,779 ...of the days when Eratosthenes walked its broad avenues. 498 00:38:23,983 --> 00:38:28,647 Over the centuries, waves of conquerors converted its palaces and temples... 499 00:38:28,855 --> 00:38:33,622 ...into castles and churches, then into minarets and mosques. 500 00:38:34,961 --> 00:38:39,364 The city was chosen to be the capital of his empire by Alexander the Great... 501 00:38:39,566 --> 00:38:43,525 ...on a winter's afternoon in 331 B.C. 502 00:38:44,070 --> 00:38:47,403 A century later, it had become the greatest city of the world. 503 00:38:47,607 --> 00:38:51,338 Each successive civilization has left its mark. 504 00:38:57,283 --> 00:39:01,743 But what now remains of the marvel city of Alexander's dream? 505 00:39:03,223 --> 00:39:06,124 Alexandria is still a thriving marketplace... 506 00:39:06,326 --> 00:39:09,591 ...still a crossroads for the peoples of the Near East. 507 00:39:16,069 --> 00:39:19,232 But once, it was radiant with self-confidence... 508 00:39:19,439 --> 00:39:21,703 ...certain of its power. 509 00:39:28,281 --> 00:39:30,374 Can you recapture a vanished epoch... 510 00:39:30,583 --> 00:39:34,952 ...from a few broken statues and scraps of ancient manuscripts? 511 00:39:42,629 --> 00:39:46,156 In Alexandria, there was an immense library... 512 00:39:46,366 --> 00:39:48,994 ...and an associated research institute. 513 00:39:49,202 --> 00:39:53,332 And in them worked the finest minds in the ancient world. 514 00:40:13,927 --> 00:40:16,361 Of that legendary library... 515 00:40:16,562 --> 00:40:19,122 ...all that survives is this... 516 00:40:19,332 --> 00:40:22,028 ...dank and forgotten cellar. 517 00:40:22,969 --> 00:40:26,905 It's in the library annex, the Serapeum... 518 00:40:27,106 --> 00:40:29,074 ...which was once a temple... 519 00:40:29,275 --> 00:40:32,073 ...but was later reconsecrated to knowledge. 520 00:40:32,612 --> 00:40:36,309 These few moldering shelves... 521 00:40:36,716 --> 00:40:39,150 ...probably once in a basement storage room... 522 00:40:39,352 --> 00:40:42,048 ...are its only physical remains. 523 00:40:42,422 --> 00:40:45,186 But this place was once... 524 00:40:45,491 --> 00:40:48,358 ...the brain and glory... 525 00:40:48,561 --> 00:40:51,689 ...of the greatest city on the planet Earth. 526 00:40:59,706 --> 00:41:02,300 If I could travel back into time... 527 00:41:02,508 --> 00:41:05,033 ...this is the place I would visit. 528 00:41:05,945 --> 00:41:10,439 The Library of Alexandria at its height, 2000 years ago. 529 00:41:14,520 --> 00:41:16,954 Here, in an important sense... 530 00:41:17,156 --> 00:41:21,456 ...began the intellectual adventure which has led us into space. 531 00:41:28,067 --> 00:41:33,004 All the knowledge in the ancient world was once within these marble walls. 532 00:41:39,112 --> 00:41:42,570 In the great hall, there may have been a mural of Alexander... 533 00:41:42,782 --> 00:41:46,013 ...with the crook and flail and ceremonial headdress... 534 00:41:46,219 --> 00:41:48,847 ...of the pharaohs of ancient Egypt. 535 00:41:52,458 --> 00:41:55,950 This library was a citadel of human consciousness... 536 00:41:56,162 --> 00:42:00,258 ...a beacon on our journey to the stars. 537 00:42:03,603 --> 00:42:08,472 It was the first true research institute in the history of the world. 538 00:42:08,741 --> 00:42:10,675 And what did they study? 539 00:42:10,977 --> 00:42:14,913 They studied everything. The entire cosmos. 540 00:42:15,114 --> 00:42:19,517 "Cosmos" is a Greek word for the order of the universe. 541 00:42:19,719 --> 00:42:22,813 In a way, it's the opposite of chaos. 542 00:42:23,056 --> 00:42:27,959 It implies a deep interconnectedness of all things. 543 00:42:28,394 --> 00:42:33,331 The intricate and subtle way that the universe is put together. 544 00:42:34,767 --> 00:42:37,463 Genius flourished here. 545 00:42:37,670 --> 00:42:42,004 In addition to Eratosthenes, there was the astronomer Hipparchus... 546 00:42:42,208 --> 00:42:43,971 ...who mapped the constellation... 547 00:42:44,177 --> 00:42:47,203 ...and established the brightness of the stars. 548 00:42:47,880 --> 00:42:49,939 And there was Euclid... 549 00:42:50,149 --> 00:42:52,982 ...who brilliantly systematized geometry... 550 00:42:53,186 --> 00:42:55,552 ...who told his king, who was struggling... 551 00:42:55,755 --> 00:42:58,383 ...with some difficult problem in mathematics... 552 00:42:58,591 --> 00:43:02,960 ...that there was no royal road to geometry. 553 00:43:03,496 --> 00:43:06,192 There was Dionysius of Thrace, the man who defined... 554 00:43:06,399 --> 00:43:09,857 ...the parts of speech: nouns, verbs and so on... 555 00:43:10,069 --> 00:43:14,005 ...who did for language, in a way, what Euclid did for geometry. 556 00:43:14,207 --> 00:43:18,234 There was Herophilus, a physiologist who identified... 557 00:43:18,444 --> 00:43:21,971 ...the brain rather than the heart as the seat of intelligence. 558 00:43:22,648 --> 00:43:25,344 There was Archimedes, the greatest mechanical genius... 559 00:43:25,551 --> 00:43:27,746 ...until the time of Leonardo da Vinci. 560 00:43:27,954 --> 00:43:32,687 And there was the astronomer Ptolemy, who compiled much of what today is... 561 00:43:32,892 --> 00:43:35,156 ...the pseudoscience of astrology. 562 00:43:35,361 --> 00:43:37,693 His Earth-centered universe... 563 00:43:37,897 --> 00:43:40,559 ...held sway for 1500 years... 564 00:43:40,766 --> 00:43:44,202 ...showing that intellectual brilliance is no guarantee... 565 00:43:44,403 --> 00:43:46,496 ...against being dead wrong. 566 00:43:46,973 --> 00:43:50,966 And among these great men, there was also a great woman. 567 00:43:51,177 --> 00:43:53,372 Her name was Hypatia. 568 00:43:53,579 --> 00:43:56,446 She was a mathematician and an astronomer... 569 00:43:56,649 --> 00:43:58,640 ...the last light of the library... 570 00:43:58,851 --> 00:44:03,754 ...whose martyrdom is bound up with the destruction of this place... 571 00:44:03,956 --> 00:44:07,255 ...seven centuries after it was founded. 572 00:44:25,645 --> 00:44:27,909 Look at this place. 573 00:44:29,115 --> 00:44:32,016 The Greek kings of Egypt who succeeded Alexander... 574 00:44:32,218 --> 00:44:35,551 ...regarded advances in science, literature and medicine... 575 00:44:35,755 --> 00:44:38,019 ...as among the treasures of the empire. 576 00:44:38,224 --> 00:44:42,684 For centuries, they generously supported research and scholarship. 577 00:44:42,895 --> 00:44:47,298 An enlightenment shared by few heads of state, then or now. 578 00:44:56,776 --> 00:45:00,735 Off this great hall were 10 large research laboratories. 579 00:45:00,947 --> 00:45:05,077 There were fountains and colonnades, botanical gardens... 580 00:45:05,284 --> 00:45:09,653 ...and even a zoo with animals from India and sub-Saharan Africa. 581 00:45:09,855 --> 00:45:14,554 There were dissecting rooms and an astronomical observatory. 582 00:45:16,562 --> 00:45:18,393 But the treasure of the library... 583 00:45:18,598 --> 00:45:21,863 ...consecrated to the god Serapis... 584 00:45:22,068 --> 00:45:24,866 ...built in the city of Alexander... 585 00:45:25,071 --> 00:45:26,902 ...was its collection of books. 586 00:45:27,106 --> 00:45:29,301 The organizers of the library combed... 587 00:45:29,508 --> 00:45:32,739 ...all the cultures and languages of the world for books. 588 00:45:32,945 --> 00:45:36,312 They sent agents abroad to buy up libraries. 589 00:45:36,515 --> 00:45:41,452 Commercial ships docking in Alexandria harbor were searched by the police... 590 00:45:41,687 --> 00:45:44,121 ...not for contraband, but for books. 591 00:45:44,323 --> 00:45:47,884 The scrolls were borrowed, copied and returned to their owners. 592 00:45:48,094 --> 00:45:52,155 Until studied, these scrolls were collected in great stacks... 593 00:45:52,365 --> 00:45:55,630 ...called, "books from the ships." 594 00:45:55,935 --> 00:45:58,369 Accurate numbers are difficult to come by... 595 00:45:58,571 --> 00:46:01,563 ...but it seems that the library contained at its peak... 596 00:46:01,774 --> 00:46:04,868 ...nearly one million scrolls. 597 00:46:18,424 --> 00:46:21,860 The papyrus reed grows in Egypt. 598 00:46:22,061 --> 00:46:24,256 It's the origin of our word for "paper." 599 00:46:24,463 --> 00:46:28,229 Each of those million volumes which once existed in this library... 600 00:46:28,434 --> 00:46:32,871 ...were handwritten on papyrus manuscript scrolls. 601 00:46:33,839 --> 00:46:35,704 What happened to all those books? 602 00:46:35,908 --> 00:46:39,344 The classical civilization that created them disintegrated. 603 00:46:39,545 --> 00:46:42,036 The library itself was destroyed. 604 00:46:42,248 --> 00:46:45,411 Only a small fraction of the works survived. 605 00:46:45,618 --> 00:46:48,746 And as for the rest, we're left only with pathetic... 606 00:46:48,954 --> 00:46:51,115 ...scattered fragments. 607 00:46:51,457 --> 00:46:55,723 But how tantalizing those remaining bits and pieces are. 608 00:46:55,928 --> 00:46:59,591 For example, we know that there once existed here... 609 00:46:59,799 --> 00:47:04,133 ...a book by the astronomer Aristarchus of Samos... 610 00:47:04,337 --> 00:47:08,467 ...who apparently argued that the Earth was one of the planets... 611 00:47:08,674 --> 00:47:12,166 ...that, like the other planets, it orbits the sun... 612 00:47:12,378 --> 00:47:16,747 ...and that the stars are enormously far away. 613 00:47:17,116 --> 00:47:19,584 All absolutely correct. 614 00:47:19,785 --> 00:47:22,413 But we had to wait nearly 2000 years... 615 00:47:22,621 --> 00:47:25,784 ...for these facts to be rediscovered. 616 00:47:32,865 --> 00:47:36,665 The astronomy stacks of the Alexandria Library. 617 00:47:37,470 --> 00:47:39,370 Hipparchus. 618 00:47:39,739 --> 00:47:42,367 Ptolomeus. Here we are. 619 00:47:43,743 --> 00:47:46,576 Aristarchus. 620 00:47:47,646 --> 00:47:49,113 This is the book. 621 00:47:49,315 --> 00:47:52,546 How I'd love to be able to read this book... 622 00:47:52,885 --> 00:47:55,854 ...to know how Aristarchus figured it out. 623 00:47:56,055 --> 00:47:59,422 But it's gone. Utterly and forever. 624 00:47:59,892 --> 00:48:04,261 If we multiply our sense of loss for this work of Aristarchus... 625 00:48:04,463 --> 00:48:05,862 ...by 100,000... 626 00:48:06,065 --> 00:48:08,533 ...we begin to appreciate the grandeur... 627 00:48:08,734 --> 00:48:11,396 ...of the achievement of classical civilization... 628 00:48:11,804 --> 00:48:14,671 ...and the tragedy of its destruction. 629 00:48:18,177 --> 00:48:22,705 We have far surpassed the science known to the ancient world... 630 00:48:22,915 --> 00:48:26,510 ...but there are irreparable gaps in our historical knowledge. 631 00:48:26,752 --> 00:48:30,119 Imagine what mysteries of the past could be solved... 632 00:48:30,322 --> 00:48:32,756 ...with a borrower's card to this library. 633 00:48:32,958 --> 00:48:37,190 For example, we know of a three-volume history of the world... 634 00:48:37,396 --> 00:48:41,890 ...now lost, written by a Babylonian priest named Berossus. 635 00:48:42,101 --> 00:48:45,730 Volume I dealt with the interval from the creation of the world... 636 00:48:45,938 --> 00:48:47,098 ...to the Great Flood. 637 00:48:47,306 --> 00:48:51,367 A period that he took to be 432,000 years... 638 00:48:51,577 --> 00:48:55,308 ...or about 100 times longer than the Old Testament chronology. 639 00:48:55,514 --> 00:48:59,416 What wonders were in the books of Berossus! 640 00:49:00,519 --> 00:49:04,546 But why have I brought you across 2000 years... 641 00:49:04,757 --> 00:49:06,987 ...to the Library of Alexandria? 642 00:49:07,760 --> 00:49:11,059 Because this was when and where we humans... 643 00:49:11,263 --> 00:49:15,359 ...first collected seriously and systematically... 644 00:49:15,568 --> 00:49:17,502 ...the knowledge of the world. 645 00:49:17,803 --> 00:49:20,294 This is the Earth as Eratosthenes knew it. 646 00:49:20,506 --> 00:49:23,771 A tiny, spherical world, afloat... 647 00:49:23,976 --> 00:49:26,968 ...in an immensity of space and time. 648 00:49:27,446 --> 00:49:30,142 We were, at long last, beginning to find... 649 00:49:30,349 --> 00:49:33,284 ...our true bearings in the cosmos. 650 00:49:34,053 --> 00:49:35,918 The scientists of antiquity... 651 00:49:36,121 --> 00:49:39,716 ...took the first and most important steps in that direction... 652 00:49:39,925 --> 00:49:42,689 ...before their civilization fell apart. 653 00:49:42,995 --> 00:49:45,862 But after the Dark Ages, it was by and large... 654 00:49:46,065 --> 00:49:50,001 ...the rediscovery of the works of these scholars done here... 655 00:49:50,202 --> 00:49:52,397 ...that made the Renaissance possible... 656 00:49:52,605 --> 00:49:55,665 ...and thereby powerfully influenced our own culture. 657 00:49:55,875 --> 00:49:59,106 When, in the 15th century, Europe was at last ready... 658 00:49:59,311 --> 00:50:02,109 ...to awaken from its long sleep... 659 00:50:02,314 --> 00:50:06,580 ...it picked up some of the tools, the books and the concepts... 660 00:50:06,785 --> 00:50:10,812 ...laid down here more than a thousand years before. 661 00:50:16,262 --> 00:50:20,164 By 1600, the long-forgotten ideas of Aristarchus... 662 00:50:20,366 --> 00:50:21,594 ...had been rediscovered. 663 00:50:22,668 --> 00:50:25,933 Johannes Kepler constructed elaborate models... 664 00:50:26,138 --> 00:50:29,039 ...to understand the motion and arrangement of the planets... 665 00:50:29,241 --> 00:50:31,903 ...the clockwork of the heavens. 666 00:50:36,015 --> 00:50:39,849 And at night, he dreamt of traveling to the moon. 667 00:50:50,563 --> 00:50:52,758 His principal scientific tools were... 668 00:50:52,965 --> 00:50:55,763 ...the mathematics of the Alexandrian Library... 669 00:50:55,968 --> 00:50:58,402 ...and an unswerving respect for the facts... 670 00:50:58,604 --> 00:51:02,040 ...however disquieting they might be. 671 00:51:05,444 --> 00:51:08,880 His story, and the story of the scientists who came after him... 672 00:51:09,081 --> 00:51:11,515 ...are also part of our voyage. 673 00:51:13,886 --> 00:51:16,855 Seventy years later, the sun-centered universe... 674 00:51:17,056 --> 00:51:18,648 ...of Aristarchus and Copernicus... 675 00:51:18,857 --> 00:51:22,725 ...was widely accepted in the Europe of the Enlightenment. 676 00:51:22,928 --> 00:51:26,364 The idea arose that the planets were worlds... 677 00:51:26,565 --> 00:51:28,192 ...governed by laws of nature... 678 00:51:28,400 --> 00:51:32,632 ...and scientific speculation turned to the motions of the stars. 679 00:51:32,838 --> 00:51:35,466 The clockwork in the heavens was imitated... 680 00:51:35,674 --> 00:51:37,437 ...by the watchmakers of Earth. 681 00:51:38,043 --> 00:51:41,535 Precise timekeeping permitted great sailing ship voyages... 682 00:51:41,747 --> 00:51:44,272 ...of exploration and discovery... 683 00:51:44,483 --> 00:51:46,041 ...which bound up the Earth. 684 00:51:48,487 --> 00:51:50,819 This was a time when free inquiry... 685 00:51:51,023 --> 00:51:52,991 ...was valued once again. 686 00:51:59,898 --> 00:52:03,299 250 years later, the Earth was all explored. 687 00:52:03,502 --> 00:52:06,665 New adventurers now looked to the planets and the stars. 688 00:52:07,406 --> 00:52:11,069 The galaxies were recognized as great aggregates of stars... 689 00:52:11,276 --> 00:52:15,212 ...island universes millions of light years away. 690 00:52:16,115 --> 00:52:19,243 In the 1920s, astronomers had begun to measure... 691 00:52:19,451 --> 00:52:22,181 ...the speeds of distant galaxies. 692 00:52:26,959 --> 00:52:27,926 What time is it? 693 00:52:28,127 --> 00:52:29,822 7:15. 694 00:52:30,262 --> 00:52:31,422 Lights off, please. 695 00:52:32,398 --> 00:52:37,028 They found that the galaxies were flying away from one another. 696 00:52:37,236 --> 00:52:39,136 To the astonishment of everyone... 697 00:52:39,338 --> 00:52:42,569 ...the entire universe was expanding. 698 00:52:48,380 --> 00:52:53,181 We had begun to plumb the true depths of time and space. 699 00:52:55,621 --> 00:52:58,317 The long, collective enterprise of science... 700 00:52:58,524 --> 00:53:02,824 ...has revealed a universe some 15 billion years old. 701 00:53:03,028 --> 00:53:06,020 The time since the explosive birth of the cosmos... 702 00:53:06,231 --> 00:53:07,465 ...the big bang. 703 00:53:07,466 --> 00:53:07,833 The current estimates for the age of the universe range from 12 to 15 billion years. 704 00:53:13,972 --> 00:53:17,999 The cosmic calendar compresses the local history of the universe... 705 00:53:18,210 --> 00:53:19,939 ...into a single year. 706 00:53:20,145 --> 00:53:22,705 If the universe began on January 1st... 707 00:53:22,915 --> 00:53:26,282 ...it was not until May that the Milky Way formed. 708 00:53:27,052 --> 00:53:29,816 Other planetary systems may have appeared... 709 00:53:30,022 --> 00:53:32,820 ...in June, July and August... 710 00:53:33,192 --> 00:53:35,922 ...but our sun and Earth, not until mid-September. 711 00:53:36,128 --> 00:53:38,494 Life arose soon after. 712 00:53:39,364 --> 00:53:43,425 Everything humans have ever done occurred in that bright speck... 713 00:53:43,635 --> 00:53:46,695 ...at the lower right of the cosmic calendar. 714 00:53:49,341 --> 00:53:51,332 The big bang is at upper left... 715 00:53:51,543 --> 00:53:54,239 ...in the first second of January 1st. 716 00:53:54,513 --> 00:53:58,210 Fifteen billion years later is our present time... 717 00:53:58,417 --> 00:54:01,784 ...the last second of December 31st. 718 00:54:06,759 --> 00:54:09,990 Every month is 1ΒΌ billion years long. 719 00:54:10,195 --> 00:54:13,096 Each day represents 40 million years. 720 00:54:13,298 --> 00:54:17,029 Each second stands for some 500 years of our history. 721 00:54:17,236 --> 00:54:21,468 The blinking of an eye in the drama of cosmic time. 722 00:54:26,845 --> 00:54:31,305 At this scale, the cosmic calendar is the size of a football field... 723 00:54:31,517 --> 00:54:34,680 ...but all of human history would occupy an area... 724 00:54:34,887 --> 00:54:36,514 ...the size of my hand. 725 00:54:36,722 --> 00:54:40,180 We're just beginning to trace the long and tortuous path... 726 00:54:40,392 --> 00:54:43,122 ...which began with the primeval fireball... 727 00:54:43,328 --> 00:54:46,024 ...and led to the condensation of matter: 728 00:54:46,231 --> 00:54:48,859 Gas, dust, stars, galaxies, and... 729 00:54:49,067 --> 00:54:51,433 ...at least in our little nook of the universe... 730 00:54:51,637 --> 00:54:55,937 ...planets, life, intelligence and inquisitive men and women. 731 00:54:56,141 --> 00:54:57,733 We've emerged so recently... 732 00:54:57,943 --> 00:55:00,810 ...that the familiar events of our recorded history... 733 00:55:01,013 --> 00:55:05,245 ...occupy only the last seconds of the last minute of December 31st. 734 00:55:05,450 --> 00:55:09,079 But some critical events for the human species began much earlier... 735 00:55:09,288 --> 00:55:11,051 ...minutes earlier. 736 00:55:12,324 --> 00:55:15,725 So we change our scale from months to minutes. 737 00:55:15,928 --> 00:55:19,091 Down here, the first humans made their debut... 738 00:55:19,298 --> 00:55:22,790 ...around 10:30 p.m. on December 31st. 739 00:55:25,671 --> 00:55:28,003 And with the passing of every cosmic minute... 740 00:55:28,207 --> 00:55:30,266 ...each minute 30,000 years long... 741 00:55:30,475 --> 00:55:32,807 ...we began the arduous journey towards understanding... 742 00:55:33,011 --> 00:55:35,673 ...where we live and who we are. 743 00:55:38,517 --> 00:55:40,610 11:46... 744 00:55:40,819 --> 00:55:43,379 ...only 14 minutes ago... 745 00:55:43,655 --> 00:55:46,624 ...humans have tamed fire. 746 00:55:47,359 --> 00:55:52,160 11:59:20, the evening of the last day of the cosmic year... 747 00:55:52,364 --> 00:55:56,198 ...the 11th hour, the 59th minute, the 20th second... 748 00:55:56,401 --> 00:55:59,268 ...the domestication of plants and animals begins: 749 00:55:59,471 --> 00:56:02,372 An application of the human talent... 750 00:56:05,244 --> 00:56:06,973 ...for making tools. 751 00:56:14,186 --> 00:56:18,680 11:59:35, settled agricultural communities... 752 00:56:18,891 --> 00:56:21,621 ...evolved into the first cities. 753 00:56:22,561 --> 00:56:26,657 We humans appear on the comic calendar so recently... 754 00:56:26,865 --> 00:56:29,265 ...that our recorded history occupies only... 755 00:56:29,468 --> 00:56:34,405 ...the last few seconds of the last minute of December 31 st. 756 00:56:35,140 --> 00:56:39,907 In the vast ocean of time which this calendar represents... 757 00:56:40,112 --> 00:56:43,479 ...all our memories are confined... 758 00:56:45,651 --> 00:56:47,881 ...to this small square. 759 00:56:48,253 --> 00:56:53,122 Every person we've ever heard of lived somewhere in there. 760 00:56:53,558 --> 00:56:58,495 All those kings and battles, migrations and inventions, wars and loves. 761 00:56:58,931 --> 00:57:00,694 Everything in the history books... 762 00:57:00,899 --> 00:57:02,833 ...happens here... 763 00:57:03,702 --> 00:57:06,933 ...in the last 10 seconds of the cosmic calendar. 764 00:57:12,377 --> 00:57:14,868 We on Earth have just awakened... 765 00:57:15,080 --> 00:57:17,878 ...to the great oceans of space and time... 766 00:57:18,083 --> 00:57:20,051 ...from which we have emerged. 767 00:57:21,353 --> 00:57:22,911 We are the legacy... 768 00:57:23,121 --> 00:57:26,613 ...of 15 billion years of cosmic evolution. 769 00:57:27,259 --> 00:57:28,954 We have a choice: 770 00:57:29,261 --> 00:57:32,753 We can enhance life and come to know the universe that made us... 771 00:57:32,965 --> 00:57:36,196 ...or we can squander our 15 billion-year heritage... 772 00:57:36,401 --> 00:57:39,336 ...in meaningless self-destruction. 773 00:57:40,572 --> 00:57:43,769 What happens in the first second of the next cosmic year... 774 00:57:43,976 --> 00:57:47,139 ...depends on what we do, here and now... 775 00:57:47,346 --> 00:57:49,143 ...with our intelligence... 776 00:57:49,348 --> 00:57:52,374 ...and our knowledge of the cosmos.