1 00:00:03,200 --> 00:00:05,400 Hello. My name is Ann Druyan. 2 00:00:05,400 --> 00:00:07,400 When Carl Sagan, Steven Soter and I... 3 00:00:07,400 --> 00:00:11,200 ...wrote the Cosmos TV series in the late 1970s... 4 00:00:11,200 --> 00:00:12,900 ...a lot of things where different. 5 00:00:12,900 --> 00:00:15,100 Back then, the U.S. and the Soviet Union... 6 00:00:15,100 --> 00:00:18,300 ...held the hole planet in their perpetual hostage crisis... 7 00:00:18,300 --> 00:00:20,200 ...called the Cold War. 8 00:00:20,200 --> 00:00:23,600 The wealth and scientific ingenuity of our civilization... 9 00:00:23,600 --> 00:00:26,300 ...was being squandered on a runaway arms raise. 10 00:00:26,300 --> 00:00:29,200 Then employed half the world scientists... 11 00:00:29,200 --> 00:00:35,100 ...and infested the world with 50.000 nuclear weapons. 12 00:00:35,100 --> 00:00:37,400 So much has happened since then. 13 00:00:37,400 --> 00:00:39,000 The Cold War is history... 14 00:00:39,000 --> 00:00:42,000 ...and science has made great strides. 15 00:00:42,000 --> 00:00:45,800 We've completed the spacecraft recognizance of the Solar System... 16 00:00:45,800 --> 00:00:49,800 ...the preliminary mapping of the visible universe that surrounds us... 17 00:00:49,800 --> 00:00:54,700 ...and we've charted the universe within: the human genome. 18 00:00:54,700 --> 00:00:58,600 When Cosmos was first broadcast there was no World Wide Web... 19 00:00:58,600 --> 00:01:00,800 ...it was a different world. 20 00:01:00,800 --> 00:01:02,900 What a tribute to Carl Sagan... 21 00:01:02,900 --> 00:01:06,600 ...a scientist who took many a punch for daring to speculate... 22 00:01:06,600 --> 00:01:11,400 ...that even after 20 of the most eventful years in the history of science... 23 00:01:11,400 --> 00:01:18,000 ...Cosmos requires few revisions and indeed is rich in prophecy. 24 00:01:18,000 --> 00:01:22,000 Cosmos is both the history of the scientific enterprise... 25 00:01:22,000 --> 00:01:26,100 ...and an attempt to convey the spiritual high... 26 00:01:26,100 --> 00:01:28,400 ...of its central revelation: 27 00:01:28,400 --> 00:01:31,300 Our oneness with the universe. 28 00:01:31,300 --> 00:01:35,300 Now, please, enjoy Cosmos, the proud saga of how... 29 00:01:35,300 --> 00:01:40,000 ...through the searching of 40.000 generations of our ancestors... 30 00:01:40,000 --> 00:01:42,400 ...we have come to discover our coordinates... 31 00:01:42,400 --> 00:01:45,300 ...in space and in time. 32 00:01:45,300 --> 00:01:50,100 And how, through the awesomely powerful method of science... 33 00:01:50,100 --> 00:01:54,700 ...we have been able to reconstruct the sweep of cosmic evolution... 34 00:01:54,700 --> 00:03:12,278 ...and defined our own part in its great story. 35 00:03:12,278 --> 00:03:15,314 SAGAN: The cosmos is all that is... 36 00:03:15,314 --> 00:03:18,818 ...or ever was or ever will be. 37 00:03:18,818 --> 00:03:23,889 Our contemplations of the cosmos stir us. 38 00:03:23,889 --> 00:03:27,793 There is a tingling in the spine, a catch in the voice... 39 00:03:27,793 --> 00:03:31,464 ...a faint sensation, as if a distant memory... 40 00:03:31,464 --> 00:03:34,033 ...of falling from a great height. 41 00:03:34,033 --> 00:03:42,875 We know we are approaching the grandest of mysteries. 42 00:03:42,875 --> 00:03:45,978 The size and age of the cosmos... 43 00:03:45,978 --> 00:03:48,647 ...are beyond ordinary human understanding. 44 00:03:48,647 --> 00:03:53,452 Lost somewhere between immensity and eternity... 45 00:03:53,452 --> 00:03:56,589 ...is our tiny planetary home, the Earth. 46 00:03:56,589 --> 00:04:00,025 For the first time, we have the power to decide... 47 00:04:00,025 --> 00:04:02,828 ...the fate of our planet and ourselves. 48 00:04:02,828 --> 00:04:04,864 This is a time of great danger. 49 00:04:04,864 --> 00:04:09,301 But our species is young and curious and brave. 50 00:04:09,301 --> 00:04:11,203 It shows much promise. 51 00:04:11,203 --> 00:04:13,539 In the last few millennia, we've made... 52 00:04:13,539 --> 00:04:16,609 ...the most astonishing and unexpected discoveries... 53 00:04:16,609 --> 00:04:20,045 ...about the cosmos and our place within it. 54 00:04:20,045 --> 00:04:23,048 I believe our future depends powerfully on... 55 00:04:23,048 --> 00:04:25,584 ...how well we understand this cosmos... 56 00:04:25,584 --> 00:04:28,921 ...in which we float like a mote of dust... 57 00:04:28,921 --> 00:04:31,457 ...in the morning sky. 58 00:04:31,457 --> 00:04:35,928 (SEA GULL CHIRPS) 59 00:04:35,928 --> 00:04:40,866 We're about to begin a journey through the cosmos. 60 00:04:40,866 --> 00:04:44,069 We'll encounter galaxies and suns and planets... 61 00:04:44,069 --> 00:04:46,205 ...life and consciousness... 62 00:04:46,205 --> 00:04:50,442 ...coming into being, evolving and perishing. 63 00:04:50,442 --> 00:04:54,113 Worlds of ice and stars of diamond. 64 00:04:54,113 --> 00:04:56,315 Atoms as massive as suns... 65 00:04:56,315 --> 00:04:59,685 ...and universes smaller than atoms. 66 00:04:59,685 --> 00:05:02,254 But it's also a story of our own planet... 67 00:05:02,254 --> 00:05:05,057 ...and the plants and animals that share it with us. 68 00:05:05,057 --> 00:05:08,327 And it's a story about us: 69 00:05:08,327 --> 00:05:11,931 How we achieved our present understanding of the cosmos... 70 00:05:11,931 --> 00:05:15,434 ...how the cosmos has shaped our evolution and our culture... 71 00:05:15,434 --> 00:05:22,274 ...and what our fate may be. 72 00:05:22,274 --> 00:05:25,811 We wish to pursue the truth, no matter where it leads. 73 00:05:25,811 --> 00:05:30,382 But to find the truth, we need imagination and skepticism both. 74 00:05:30,382 --> 00:05:32,852 We will not be afraid to speculate. 75 00:05:32,852 --> 00:05:37,489 But we will be careful to distinguish speculation from fact. 76 00:05:37,489 --> 00:05:42,328 The cosmos is full beyond measure of elegant truths... 77 00:05:42,328 --> 00:05:44,830 ...of exquisite interrelationships... 78 00:05:44,830 --> 00:05:49,101 ...of the awesome machinery of nature. 79 00:05:49,101 --> 00:05:53,873 The surface of the Earth is the shore of the cosmic ocean. 80 00:05:53,873 --> 00:05:57,443 On this shore, we have learned most of what we know. 81 00:05:57,443 --> 00:06:00,212 Recently, we've waded a little way out... 82 00:06:00,212 --> 00:06:04,917 ...maybe ankle-deep, and the water seems inviting. 83 00:06:04,917 --> 00:06:09,688 Some part of our being knows this is where we came from. 84 00:06:09,688 --> 00:06:12,491 We long to return. 85 00:06:12,491 --> 00:06:13,792 And we can. 86 00:06:13,792 --> 00:06:18,130 Because the cosmos is also within us. We're made of star-stuff. 87 00:06:18,130 --> 00:06:22,868 We are a way for the cosmos to know itself. 88 00:06:22,868 --> 00:06:25,871 The journey for each of us begins here. 89 00:06:25,871 --> 00:06:29,775 We're going to explore the cosmos in a ship of the imagination... 90 00:06:29,775 --> 00:06:34,213 ...unfettered by ordinary limits on speed and size... 91 00:06:34,213 --> 00:06:37,149 ...drawn by the music of cosmic harmonies... 92 00:06:37,149 --> 00:06:40,486 ...it can take us anywhere in space and time. 93 00:06:40,486 --> 00:06:42,955 Perfect as a snowflake... 94 00:06:42,955 --> 00:06:46,725 ...organic as a dandelion seed... 95 00:06:46,725 --> 00:06:48,093 ...it will carry us... 96 00:06:48,093 --> 00:06:52,932 ...to worlds of dreams and worlds of facts. 97 00:06:52,932 --> 00:07:05,077 Come with me. 98 00:07:05,077 --> 00:07:15,387 Before us is the cosmos on the grandest scale we know. 99 00:07:15,387 --> 00:07:18,023 We are far from the shores of Earth... 100 00:07:18,023 --> 00:07:21,360 ...in the uncharted reaches of the cosmic ocean. 101 00:07:21,360 --> 00:07:25,064 Strewn like sea froth on the waves of space... 102 00:07:25,064 --> 00:07:28,000 ...are innumerable faint tendrils of light. 103 00:07:28,000 --> 00:07:30,569 Some of them containing hundreds... 104 00:07:30,569 --> 00:07:33,973 ...of billions of suns. 105 00:07:33,973 --> 00:07:36,842 These are the galaxies... 106 00:07:36,842 --> 00:07:43,582 ...drifting endlessly in the great cosmic dark. 107 00:07:43,582 --> 00:07:45,784 In our ship of the imagination... 108 00:07:45,784 --> 00:07:59,198 ...we are halfway to the edge of the known universe. 109 00:07:59,198 --> 00:08:02,901 In this, the first of our cosmic voyages... 110 00:08:02,901 --> 00:08:14,413 ...we begin to explore the universe revealed by science. 111 00:08:14,413 --> 00:08:19,518 Our course will eventually carry us to a far-off and exotic world. 112 00:08:19,518 --> 00:08:22,721 But from the depths of space, we cannot detect even... 113 00:08:22,721 --> 00:08:26,158 ...the cluster of galaxies in which our Milky Way is embedded... 114 00:08:26,158 --> 00:08:45,377 ...much less the sun or the Earth. 115 00:08:45,377 --> 00:08:48,013 We are in the realm of the galaxies... 116 00:08:48,013 --> 00:08:56,221 ...8 billion light years from home. 117 00:08:56,221 --> 00:09:01,060 No matter where we travel, the patterns of nature are the same... 118 00:09:01,060 --> 00:09:06,665 ...as in the form of this spiral galaxy. 119 00:09:06,665 --> 00:09:09,701 The same laws of physics apply everywhere... 120 00:09:09,701 --> 00:09:17,076 ...throughout the cosmos. 121 00:09:17,076 --> 00:09:20,379 But we have just begun to understand these laws. 122 00:09:20,379 --> 00:09:29,121 The universe is rich in mystery. 123 00:09:29,121 --> 00:09:31,890 Near the center of a cluster of galaxies... 124 00:09:31,890 --> 00:09:35,894 ...there's sometimes a rogue, elliptical galaxy... 125 00:09:35,894 --> 00:09:38,163 ...made of a trillion suns... 126 00:09:38,163 --> 00:09:40,566 ...which devours its neighbors. 127 00:09:40,566 --> 00:09:43,001 Perhaps this cyclone of stars... 128 00:09:43,001 --> 00:10:02,087 ...is what astronomers on Earth call a quasar. 129 00:10:02,087 --> 00:10:05,691 Our ordinary measures of distance fail us... 130 00:10:05,691 --> 00:10:08,660 ...here in the realm of the galaxies. 131 00:10:08,660 --> 00:10:11,463 We need a much larger unit: the light year. 132 00:10:11,463 --> 00:10:14,233 It measures how far light travels in a year... 133 00:10:14,233 --> 00:10:17,336 ...nearly 10 trillion kilometers. 134 00:10:17,336 --> 00:10:35,654 It measures not time, but enormous distances. 135 00:10:35,654 --> 00:10:37,589 In the Hercules cluster... 136 00:10:37,589 --> 00:10:42,261 ...the individual galaxies are about 300,000 light years apart. 137 00:10:42,261 --> 00:10:46,198 So light takes about 300,000 years... 138 00:10:46,198 --> 00:10:52,704 ...to go from one galaxy to another. 139 00:10:52,704 --> 00:10:56,475 Like stars and planets and people... 140 00:10:56,475 --> 00:11:01,146 ...galaxies are born, live and die. 141 00:11:01,146 --> 00:11:05,350 They may all experience a tumultuous adolescence. 142 00:11:05,350 --> 00:11:09,688 During their first 100 million years, their cores may explode. 143 00:11:09,688 --> 00:11:12,824 Seen in radio light, great jets of energy... 144 00:11:12,824 --> 00:11:17,062 ...pour out and echo across the cosmos. 145 00:11:17,062 --> 00:11:22,301 Worlds near the core or along the jets would be incinerated. 146 00:11:22,301 --> 00:11:26,471 I wonder how many planets and how many civilizations... 147 00:11:26,471 --> 00:11:36,415 ...might be destroyed. 148 00:11:36,415 --> 00:11:40,452 In the Pegasus cluster, there's a ring galaxy... 149 00:11:40,452 --> 00:11:43,822 ...the wreckage left from the collision of two galaxies. 150 00:11:43,822 --> 00:11:47,859 A splash in the cosmic pond. 151 00:11:47,859 --> 00:11:51,496 Individual galaxies may explode and collide... 152 00:11:51,496 --> 00:11:55,834 ...and their constituent stars may blow up as well. 153 00:11:55,834 --> 00:11:58,403 In this supernova explosion... 154 00:11:58,403 --> 00:12:05,277 ...a single star outshines the rest of its galaxy. 155 00:12:05,277 --> 00:12:08,947 We are approaching what astronomers on Earth call... 156 00:12:08,947 --> 00:12:12,951 ...the Local Group. 157 00:12:12,951 --> 00:12:18,924 Three million light years across, it contains some 20 galaxies. 158 00:12:18,924 --> 00:12:22,761 It's a sparse and rather typical chain of islands... 159 00:12:22,761 --> 00:12:26,598 ...in the immense cosmic ocean. 160 00:12:26,598 --> 00:12:31,803 We are now only 2 million light years from home. 161 00:12:31,803 --> 00:12:35,440 On the maps of space, this galaxy is called M31... 162 00:12:35,440 --> 00:12:37,843 ...the great galaxy Andromeda. 163 00:12:37,843 --> 00:12:41,647 It's a vast storm of stars and gas and dust. 164 00:12:41,647 --> 00:12:43,148 As we pass over it... 165 00:12:43,148 --> 00:12:50,656 ...we see one of its small satellite galaxies. 166 00:12:50,656 --> 00:12:52,491 Clusters of galaxies... 167 00:12:52,491 --> 00:12:55,260 ...and the stars of individual galaxies... 168 00:12:55,260 --> 00:12:58,196 ...are all held together by gravity. 169 00:12:58,196 --> 00:13:00,132 Surrounding M31... 170 00:13:00,132 --> 00:13:04,870 ...are hundreds of globular star clusters. 171 00:13:04,870 --> 00:13:07,472 We're approaching one of them. 172 00:13:07,472 --> 00:13:11,276 Each cluster orbits the massive center of the galaxy. 173 00:13:11,276 --> 00:13:15,914 Some contain up to a million separate stars. 174 00:13:15,914 --> 00:13:19,685 Every globular cluster is like a swarm of bees... 175 00:13:19,685 --> 00:13:21,286 ...bound by gravity... 176 00:13:21,286 --> 00:13:26,658 ...every bee, a sun. 177 00:13:26,658 --> 00:13:29,361 From Pegasus, our voyage has taken us... 178 00:13:29,361 --> 00:13:33,098 ...200 million light years to the Local Group... 179 00:13:33,098 --> 00:13:38,537 ...dominated by two great spiral galaxies. 180 00:13:38,537 --> 00:13:42,574 Beyond M31 is another very similar galaxy. 181 00:13:42,574 --> 00:13:45,210 Its spiral arms slowly turning... 182 00:13:45,210 --> 00:13:54,286 ...once every quarter billion years. 183 00:13:54,286 --> 00:13:57,289 This is our own Milky Way... 184 00:13:57,289 --> 00:14:06,431 ...seen from the outside. 185 00:14:06,431 --> 00:14:18,577 This is the home galaxy of the human species. 186 00:14:18,577 --> 00:14:23,782 In the obscure backwaters of the Carina-Cygnus spiral arm... 187 00:14:23,782 --> 00:14:27,252 ...we humans have evolved to consciousness... 188 00:14:27,252 --> 00:14:30,088 ...and some measure of understanding. 189 00:14:30,088 --> 00:14:33,625 This region of the Milky Way galaxy is now usually called the Local Arm... 190 00:14:33,625 --> 00:14:38,630 ...or the Orion Arm, but the spiral arm nomenclature remains rather fuzzy. 191 00:14:38,630 --> 00:14:41,566 Concentrated in its brilliant core... 192 00:14:41,566 --> 00:14:44,503 ...and strewn along its spiral arms... 193 00:14:44,503 --> 00:14:50,909 ...are 400 billion suns. 194 00:14:50,909 --> 00:14:53,612 It takes light 100,000 years to travel... 195 00:14:53,612 --> 00:14:58,617 ...from one end of the galaxy to the other. 196 00:14:58,617 --> 00:15:02,788 Within this galaxy are stars and worlds... 197 00:15:02,788 --> 00:15:07,325 ...and, it may be, an enormous diversity of living things... 198 00:15:07,325 --> 00:15:20,172 ...and intelligent beings and space faring civilizations. 199 00:15:20,172 --> 00:15:23,175 Scattered among the stars of the Milky Way... 200 00:15:23,175 --> 00:15:25,343 ...are supernova remnants... 201 00:15:25,343 --> 00:15:29,881 ...each one the remains of a colossal stellar explosion. 202 00:15:29,881 --> 00:15:32,117 These filaments of glowing gas... 203 00:15:32,117 --> 00:15:36,354 ...are the outer layers of a star which has recently destroyed itself. 204 00:15:36,354 --> 00:15:38,290 The gas is unraveling... 205 00:15:38,290 --> 00:15:42,060 ...returning star-stuff back into space. 206 00:15:42,060 --> 00:15:46,031 (PULSAR HISSES) 207 00:15:46,031 --> 00:15:49,501 And at its heart, are the remains of the original star... 208 00:15:49,501 --> 00:15:54,372 ...a dense, shrunken stellar fragment called a pulsar. 209 00:15:54,372 --> 00:15:57,909 A natural lighthouse, blinking and hissing. 210 00:15:57,909 --> 00:16:07,252 A sun that spins twice each second. 211 00:16:07,252 --> 00:16:10,822 Pulsars keep such perfect time that the first one discovered... 212 00:16:10,822 --> 00:16:13,925 ...was thought to be a sign of extraterrestrial intelligence. 213 00:16:13,925 --> 00:16:16,495 Perhaps a navigational beacon... 214 00:16:16,495 --> 00:16:19,764 ...for great ships that travel across the light years... 215 00:16:19,764 --> 00:16:25,437 ...and between the stars. 216 00:16:25,437 --> 00:16:29,241 There may be such intelligences and such starships... 217 00:16:29,241 --> 00:16:43,188 ...but pulsars are not their signature. 218 00:16:43,188 --> 00:16:46,791 Instead, they are the doleful reminders... 219 00:16:46,791 --> 00:16:48,760 ...that nothing lasts forever... 220 00:16:48,760 --> 00:16:54,099 ...that stars also die. 221 00:16:54,099 --> 00:16:58,236 We continue to plummet, falling thousands of light years... 222 00:16:58,236 --> 00:17:03,108 ...towards the plane of the galaxy. 223 00:17:03,108 --> 00:17:04,943 This is the Milky Way... 224 00:17:04,943 --> 00:17:07,612 ...our galaxy seen edge on. 225 00:17:07,612 --> 00:17:09,915 Billions of nuclear furnaces... 226 00:17:09,915 --> 00:17:17,889 ...converting matter into starlight. 227 00:17:17,889 --> 00:17:20,992 Some stars are flimsy as a soap bubble. 228 00:17:20,992 --> 00:17:25,564 Others are 100 trillion times denser than lead. 229 00:17:25,564 --> 00:17:29,534 The hottest stars are destined to die young. 230 00:17:29,534 --> 00:17:33,004 But red giants are mostly elderly. 231 00:17:33,004 --> 00:17:39,978 Such stars are unlikely to have inhabited planets. 232 00:17:39,978 --> 00:17:42,881 But yellow dwarf stars, like the sun... 233 00:17:42,881 --> 00:17:47,452 ...are middle-aged and they are far more common. 234 00:17:47,452 --> 00:17:50,589 These stars may have planetary systems. 235 00:17:50,589 --> 00:17:54,392 And on such planets, for the first time on our cosmic voyage... 236 00:17:54,392 --> 00:17:57,095 ...we encounter rare forms of matter: 237 00:17:57,095 --> 00:18:06,638 Ice and rock, air and liquid water. 238 00:18:06,638 --> 00:18:08,506 Close to this yellow star... 239 00:18:08,506 --> 00:18:11,710 ...is a small, warm, cloudy world... 240 00:18:11,710 --> 00:18:14,079 ...with continents and oceans. 241 00:18:14,079 --> 00:18:19,417 These conditions permit an even more precious form of matter to arise: 242 00:18:19,417 --> 00:18:27,926 Life. 243 00:18:27,926 --> 00:18:29,995 But this is not the Earth. 244 00:18:29,995 --> 00:18:34,866 Intelligent beings have evolved and reworked this planetary surface... 245 00:18:34,866 --> 00:18:37,936 ...in a massive engineering enterprise. 246 00:18:37,936 --> 00:18:41,373 In the Milky Way galaxy, there may be many worlds... 247 00:18:41,373 --> 00:18:52,083 ...on which matter has grown to consciousness. 248 00:18:52,083 --> 00:18:55,620 I wonder, are they very different from us? 249 00:18:55,620 --> 00:18:57,255 What do they look like? 250 00:18:57,255 --> 00:19:01,860 What are their politics, technology, music, religion? 251 00:19:01,860 --> 00:19:06,564 Or do they have patterns of culture we can't begin to imagine? 252 00:19:06,564 --> 00:19:17,709 Are they also a danger to themselves? 253 00:19:17,709 --> 00:19:21,446 Among the many glowing clouds of interstellar gas... 254 00:19:21,446 --> 00:19:24,683 ...is one called the Orion Nebula... 255 00:19:24,683 --> 00:19:33,224 ...only 1500 light years from Earth. 256 00:19:33,224 --> 00:19:36,828 These three bright stars are seen by earthlings... 257 00:19:36,828 --> 00:19:48,039 ...as the belt in the familiar constellation of Orion the hunter. 258 00:19:48,039 --> 00:19:51,409 The nebula appears from Earth as a patch of light... 259 00:19:51,409 --> 00:20:03,621 ...the middle star in Orion's sword. 260 00:20:03,621 --> 00:20:06,291 But it is not a star. 261 00:20:06,291 --> 00:20:09,427 It is another thing entirely. 262 00:20:09,427 --> 00:20:23,241 A cloud that veils one of nature's secret places. 263 00:20:23,241 --> 00:20:28,413 This is a stellar nursery, a place where stars are born. 264 00:20:28,413 --> 00:20:31,382 They condense by gravity from gas and dust... 265 00:20:31,382 --> 00:20:36,755 ...until their temperatures become so high that they begin to shine. 266 00:20:36,755 --> 00:20:39,691 Such clouds mark the births of stars... 267 00:20:39,691 --> 00:20:48,633 ...as others bear witness to their deaths. 268 00:20:48,633 --> 00:20:53,071 After stars condense in the hidden interiors of interstellar clouds... 269 00:20:53,071 --> 00:20:54,773 ...what happens to them? 270 00:20:54,773 --> 00:20:58,510 The Pleiades are a loose cluster of young stars... 271 00:20:58,510 --> 00:21:00,779 ...only 50 million years old. 272 00:21:00,779 --> 00:21:05,950 These fledgling stars are just being let out into the galaxy. 273 00:21:05,950 --> 00:21:09,354 Still surrounded by wisps of nebulosity... 274 00:21:09,354 --> 00:21:47,292 ...the gas and dust from which they formed. 275 00:21:47,292 --> 00:21:50,862 There are clouds that hang like inkblots... 276 00:21:50,862 --> 00:21:52,697 ...between the stars. 277 00:21:52,697 --> 00:21:55,700 They are made of fine, rocky dust... 278 00:21:55,700 --> 00:21:59,804 ...organic matter and ice. 279 00:21:59,804 --> 00:22:04,008 Inside, a few stars begin to turn on. 280 00:22:04,008 --> 00:22:06,110 Nearby worlds of ice evaporate... 281 00:22:06,110 --> 00:22:08,913 ...and form long, comet-like tails... 282 00:22:08,913 --> 00:22:16,788 ...driven back by the stellar winds. 283 00:22:16,788 --> 00:22:20,258 Black clouds, light years across... 284 00:22:20,258 --> 00:22:22,427 ...drift between the stars. 285 00:22:22,427 --> 00:22:25,563 They're filled with organic molecules. 286 00:22:25,563 --> 00:22:28,633 The building blocks of life are everywhere. 287 00:22:28,633 --> 00:22:30,802 They are easily made. 288 00:22:30,802 --> 00:22:36,007 On how many worlds have such complex molecules assembled themselves... 289 00:22:36,007 --> 00:22:45,016 ...into patterns we would call alive? 290 00:22:45,016 --> 00:22:50,088 Most stars belong to systems of two or three or many suns... 291 00:22:50,088 --> 00:22:52,290 ...bound together by gravity. 292 00:22:52,290 --> 00:22:55,727 Each system is isolated from its neighbors... 293 00:22:55,727 --> 00:22:59,597 ...by the light years. 294 00:22:59,597 --> 00:23:03,601 We are approaching a single, ordinary, yellow dwarf star... 295 00:23:03,601 --> 00:23:06,504 ...surrounded by a system of nine planets... 296 00:23:06,504 --> 00:23:11,209 ...dozens of moons, thousands of asteroids and billions of comets: 297 00:23:11,209 --> 00:23:14,979 The family of the sun. 298 00:23:14,979 --> 00:23:19,450 Only four light hours from Earth is the planet Neptune... 299 00:23:19,450 --> 00:23:25,957 ...and its giant satellite, Triton. 300 00:23:25,957 --> 00:23:29,027 Even in the outskirts of our own solar system... 301 00:23:29,027 --> 00:23:35,566 ...we humans have barely begun our explorations. 302 00:23:35,566 --> 00:23:37,168 Only a century ago... 303 00:23:37,168 --> 00:23:41,239 ...we were ignorant even of the existence of the planet Pluto. 304 00:23:41,239 --> 00:23:43,574 Its moon, Charon, remained undiscovered until 1978. 305 00:23:43,574 --> 00:23:48,446 Since the discovery of Kuiper Belt objects in 1992, Pluto has come to be seen... 306 00:23:48,446 --> 00:23:51,149 ...as the largest member of this population of comets. 307 00:23:51,149 --> 00:23:51,516 The rings of Uranus were first detected in 1977. 308 00:23:51,516 --> 00:23:55,820 Many astronomers no longer regard it as a planet. 309 00:23:55,820 --> 00:24:03,127 There are new worlds to chart even this close to home. 310 00:24:03,127 --> 00:24:06,664 Saturn is a giant gas world. 311 00:24:06,664 --> 00:24:08,833 If it has a solid surface... 312 00:24:08,833 --> 00:24:14,272 ...it must lie far below the clouds we see. 313 00:24:14,272 --> 00:24:16,407 Saturn's majestic rings... 314 00:24:16,407 --> 00:24:25,550 ...are made of trillions of orbiting snowballs. 315 00:24:25,550 --> 00:24:29,787 We are now only 80 light minutes from home. 316 00:24:29,787 --> 00:24:47,105 A mere 1 1/2 billion kilometers. 317 00:24:47,105 --> 00:24:51,175 The largest planet in our solar system is Jupiter. 318 00:24:51,175 --> 00:24:55,713 On its dark side, super bolts of lightning illuminate the clouds... 319 00:24:55,713 --> 00:25:12,764 ...as first revealed by the Voyager spacecraft in 1979. 320 00:25:12,764 --> 00:25:14,799 Inside the orbit of Jupiter... 321 00:25:14,799 --> 00:25:18,603 ...are countless shattered and broken world-lets: 322 00:25:18,603 --> 00:25:20,405 The asteroids. 323 00:25:20,405 --> 00:25:22,707 These reefs and shoals... 324 00:25:22,707 --> 00:25:26,077 ...mark the border of the realm of giant planets. 325 00:25:26,077 --> 00:25:32,216 We are now entering the shallows of the solar system. 326 00:25:32,216 --> 00:25:36,754 Here there are worlds with thin atmospheres and solid surfaces: 327 00:25:36,754 --> 00:25:38,289 Earth-like planets... 328 00:25:38,289 --> 00:25:42,527 ...with landscapes crying out for careful exploration. 329 00:25:42,527 --> 00:25:47,999 This world is Mars. 330 00:25:47,999 --> 00:25:51,702 In 1976, after a year's voyage... 331 00:25:51,702 --> 00:25:54,405 ...two robot explorers from Earth... 332 00:25:54,405 --> 00:25:58,876 ...landed on this alien shore. 333 00:25:58,876 --> 00:26:02,680 On Mars, there is a volcano as wide as Arizona... 334 00:26:02,680 --> 00:26:05,650 ...and almost three times the height of Mount Everest. 335 00:26:05,650 --> 00:26:13,491 We've named it Mount Olympus. 336 00:26:13,491 --> 00:26:18,096 This is a world of wonders. 337 00:26:18,096 --> 00:26:20,932 Mars is a planet with ancient river valleys... 338 00:26:20,932 --> 00:26:33,077 ...and violent sandstorms driven by winds at half the speed of sound. 339 00:26:33,077 --> 00:26:38,116 There is a giant rift in its surface 5000 kilometers long. 340 00:26:38,116 --> 00:26:41,786 It's called Vallis Marinaris. 341 00:26:41,786 --> 00:26:44,322 The valley of the Mariner spacecraft... 342 00:26:44,322 --> 00:27:06,744 ...that came to explore Mars from a nearby world. 343 00:27:06,744 --> 00:27:10,214 In this, our first cosmic voyage... 344 00:27:10,214 --> 00:27:13,251 ...we have just begun the reconnaissance of Mars... 345 00:27:13,251 --> 00:27:16,921 ...and all those other planets and stars and galaxies. 346 00:27:16,921 --> 00:27:28,733 In voyages to come, we will explore them more fully. 347 00:27:28,733 --> 00:27:32,603 But now, we travel the few remaining light minutes... 348 00:27:32,603 --> 00:27:37,742 ...to a blue and cloudy world, third from the sun. 349 00:27:37,742 --> 00:27:40,011 The end of our long journey... 350 00:27:40,011 --> 00:27:42,747 ...is the world where we began. 351 00:27:42,747 --> 00:27:44,782 Our travels allow us... 352 00:27:44,782 --> 00:27:47,251 ...to see the Earth anew... 353 00:27:47,251 --> 00:27:52,757 ...as if we came from somewhere else. 354 00:27:52,757 --> 00:27:55,593 There are a hundred billion galaxies... 355 00:27:55,593 --> 00:27:58,796 ...and a billion trillion stars. 356 00:27:58,796 --> 00:28:03,601 Why should this modest planet be the only inhabited world? 357 00:28:03,601 --> 00:28:08,406 To me, it seems far more likely that the cosmos is brimming over... 358 00:28:08,406 --> 00:28:10,741 ...with life and intelligence. 359 00:28:10,741 --> 00:28:13,611 But so far, every living thing... 360 00:28:13,611 --> 00:28:15,413 ...every conscious being... 361 00:28:15,413 --> 00:28:18,316 ...every civilization we know anything about... 362 00:28:18,316 --> 00:28:28,259 ...lived there, on Earth. 363 00:28:28,259 --> 00:28:30,094 Beneath these clouds... 364 00:28:30,094 --> 00:28:36,367 ...the drama of the human species has been unfolded. 365 00:28:36,367 --> 00:28:49,313 We have, at last, come home. 366 00:28:49,313 --> 00:28:51,849 Welcome to the planet Earth. 367 00:28:51,849 --> 00:28:54,885 A place with blue nitrogen skies... 368 00:28:54,885 --> 00:28:56,988 ...oceans of liquid water... 369 00:28:56,988 --> 00:28:58,522 ...cool forests... 370 00:28:58,522 --> 00:29:00,124 ...soft meadows. 371 00:29:00,124 --> 00:29:04,295 A world positively rippling with life. 372 00:29:04,295 --> 00:29:08,032 In the cosmic perspective, it is, for the moment, unique. 373 00:29:08,032 --> 00:29:10,868 The only world in which we know with certainty... 374 00:29:10,868 --> 00:29:15,106 ...that the matter of the cosmos has become alive and aware. 375 00:29:15,106 --> 00:29:18,142 There must be many such worlds scattered through space... 376 00:29:18,142 --> 00:29:20,778 ...but our search for them begins here... 377 00:29:20,778 --> 00:29:24,382 ...with the accumulated wisdom of the men and women of our species... 378 00:29:24,382 --> 00:29:26,384 ...acquired at great cost... 379 00:29:26,384 --> 00:30:11,662 ...over a million years. 380 00:30:11,662 --> 00:30:14,765 There was once a time when our planet seemed immense. 381 00:30:14,765 --> 00:30:17,468 When it was the only world we could explore. 382 00:30:17,468 --> 00:30:21,906 Its true size was first worked out in a simple and ingenious way... 383 00:30:21,906 --> 00:30:32,116 ...by a man who lived here in Egypt, in the third century B.C. 384 00:30:32,116 --> 00:30:36,587 This tower may have been a communications tower. 385 00:30:36,587 --> 00:30:40,558 Part of a network running along the North African coast... 386 00:30:40,558 --> 00:30:45,162 ...by which signal bonfires were used to communicate messages of state. 387 00:30:45,162 --> 00:30:49,767 It also may have been used as a lighthouse... 388 00:30:49,767 --> 00:30:53,237 ...a navigational beacon for sailing ships... 389 00:30:53,237 --> 00:30:55,773 ...out there in the Mediterranean Sea. 390 00:30:55,773 --> 00:30:58,509 It is about 50 kilometers west... 391 00:30:58,509 --> 00:31:04,115 ...of what was once one of the great cities of the world, Alexandria. 392 00:31:04,115 --> 00:31:06,350 In Alexandria, at that time... 393 00:31:06,350 --> 00:31:09,587 ...there lived a man named Eratosthenes. 394 00:31:09,587 --> 00:31:14,291 A competitor called him "beta," the second letter of the Greek alphabet... 395 00:31:14,291 --> 00:31:19,196 ...because, he said, "Eratosthenes was second best in everything." 396 00:31:19,196 --> 00:31:24,135 But it seems clear, in many fields, Eratosthenes was "alpha." 397 00:31:24,135 --> 00:31:28,038 He was an astronomer, historian, geographer... 398 00:31:28,038 --> 00:31:32,109 ...philosopher, poet, theater critic and mathematician. 399 00:31:32,109 --> 00:31:36,714 He was also the chief librarian of the Great Library of Alexandria. 400 00:31:36,714 --> 00:31:41,852 And one day while reading a papyrus book in the library... 401 00:31:41,852 --> 00:31:53,030 ...he came upon a curious account. 402 00:31:53,030 --> 00:31:55,065 Far to the south, he read... 403 00:31:55,065 --> 00:31:57,601 ...at the frontier outpost of Syene... 404 00:31:57,601 --> 00:32:06,076 ...something notable could be seen on the longest day of the year. 405 00:32:06,076 --> 00:32:07,812 On June 21st... 406 00:32:07,812 --> 00:32:11,081 ...the shadows of a temple column, or a vertical stick... 407 00:32:11,081 --> 00:32:19,623 ...would grow shorter as noon approached. 408 00:32:19,623 --> 00:32:21,459 As the hours crept towards midday... 409 00:32:21,459 --> 00:32:25,896 ...the sun's rays would slither down the sides of a deep well... 410 00:32:25,896 --> 00:32:35,339 ...which on other days would remain in shadow. 411 00:32:35,339 --> 00:32:38,175 And then, precisely at noon... 412 00:32:38,175 --> 00:32:40,778 ...columns would cast no shadows. 413 00:32:40,778 --> 00:32:51,455 And the sun would shine directly down into the water of the well. 414 00:32:51,455 --> 00:32:53,090 At that moment... 415 00:32:53,090 --> 00:33:00,831 ...the sun was exactly overhead. 416 00:33:00,831 --> 00:33:05,369 It was an observation that someone else might easily have ignored. 417 00:33:05,369 --> 00:33:09,440 Sticks, shadows, reflections in wells... 418 00:33:09,440 --> 00:33:11,375 ...the position of the sun... 419 00:33:11,375 --> 00:33:13,611 ...simple, everyday matters. 420 00:33:13,611 --> 00:33:17,047 Of what possible importance might they be? 421 00:33:17,047 --> 00:33:19,950 But Eratosthenes was a scientist... 422 00:33:19,950 --> 00:33:23,621 ...and his contemplation of these homely matters changed the world... 423 00:33:23,621 --> 00:33:26,090 ...in a way, made the world. 424 00:33:26,090 --> 00:33:30,427 Because Eratosthenes had the presence of mind to experiment... 425 00:33:30,427 --> 00:33:35,099 ...to actually ask whether back here, near Alexandria... 426 00:33:35,099 --> 00:33:40,404 ...a stick cast a shadow near noon on June the 21 st. 427 00:33:40,404 --> 00:33:45,476 And it turns out, sticks do. 428 00:33:45,476 --> 00:33:48,112 An overly skeptical person might have said... 429 00:33:48,112 --> 00:33:50,981 ...that the report from Syene was an error. 430 00:33:50,981 --> 00:33:53,984 But it's an absolutely straightforward observation. 431 00:33:53,984 --> 00:33:57,354 Why would anyone lie on such a trivial matter? 432 00:33:57,354 --> 00:34:00,291 Eratosthenes asked himself how it could be... 433 00:34:00,291 --> 00:34:02,526 ...that at the same moment... 434 00:34:02,526 --> 00:34:05,396 ...a stick in Syene would cast no shadow... 435 00:34:05,396 --> 00:34:09,166 ...and a stick in Alexandria, 800 kilometers to the north... 436 00:34:09,166 --> 00:34:14,805 ...would cast a very definite shadow. 437 00:34:14,805 --> 00:34:18,909 Here is a map of ancient Egypt. 438 00:34:18,909 --> 00:34:22,479 I've inserted two sticks, or obelisks. 439 00:34:22,479 --> 00:34:27,151 One up here in Alexandria and one down here in Syene. 440 00:34:27,151 --> 00:34:31,188 Now, if at a certain moment each stick casts... 441 00:34:31,188 --> 00:34:33,958 ...no shadow, no shadow at all... 442 00:34:33,958 --> 00:34:38,429 ...that's perfectly easy to understand, provided the Earth is flat. 443 00:34:38,429 --> 00:34:41,832 If the shadow at Syene is at a certain length... 444 00:34:41,832 --> 00:34:44,468 ...and the shadow at Alexandria is the same length... 445 00:34:44,468 --> 00:34:47,504 ...that also makes sense on a flat Earth. 446 00:34:47,504 --> 00:34:50,941 But how could it be, Eratosthenes asked... 447 00:34:50,941 --> 00:34:55,779 ...that at the same instant there was no shadow at Syene... 448 00:34:55,779 --> 00:35:01,785 ...and a very substantial shadow at Alexandria? 449 00:35:01,785 --> 00:35:06,590 The only answer was that the surface of the Earth is curved. 450 00:35:06,590 --> 00:35:08,125 Not only that... 451 00:35:08,125 --> 00:35:12,129 ...but the greater the curvature, the bigger the difference... 452 00:35:12,129 --> 00:35:16,033 ...in the lengths of the shadows. The sun is so far away... 453 00:35:16,033 --> 00:35:18,669 ...that its rays are parallel when they reach the Earth. 454 00:35:18,669 --> 00:35:23,140 Sticks at different angles to the sun will cast shadows at different lengths. 455 00:35:23,140 --> 00:35:26,777 For the observed difference in the shadow lengths... 456 00:35:26,777 --> 00:35:29,413 ...the distance between Alexandria and Syene... 457 00:35:29,413 --> 00:35:33,517 ...had to be about seven degrees along the surface of the Earth. 458 00:35:33,517 --> 00:35:37,621 By that, I mean, if you would imagine these sticks extending... 459 00:35:37,621 --> 00:35:40,324 ...all the way down to the center of the Earth... 460 00:35:40,324 --> 00:35:43,627 ...they would there intersect at an angle of seven degrees. 461 00:35:43,627 --> 00:35:46,997 Well, seven degrees is something like a 50th... 462 00:35:46,997 --> 00:35:50,768 ...of the full circumference of the Earth, 360 degrees. 463 00:35:50,768 --> 00:35:55,506 Eratosthenes knew the distance between Alexandria and Syene. 464 00:35:55,506 --> 00:35:57,675 He knew it was 800 kilometers. 465 00:35:57,675 --> 00:36:02,479 Why? Because he hired a man to pace out the entire distance... 466 00:36:02,479 --> 00:36:06,150 ...so that he could perform the calculation I'm talking about. 467 00:36:06,150 --> 00:36:11,088 Now, 800 kilometers times 50 is 40,000 kilometers. 468 00:36:11,088 --> 00:36:13,390 That must be the circumference of the Earth. 469 00:36:13,390 --> 00:36:17,061 That's how far it is to go once around the Earth. 470 00:36:17,061 --> 00:36:18,729 That's the right answer. 471 00:36:18,729 --> 00:36:21,265 Eratosthenes' only tools were... 472 00:36:21,265 --> 00:36:25,669 ...sticks, eyes, feet and brains. 473 00:36:25,669 --> 00:36:29,406 Plus a zest for experiment. 474 00:36:29,406 --> 00:36:33,343 With those tools, he correctly deduced the circumference of the Earth... 475 00:36:33,343 --> 00:36:38,916 ...to high precision with an error of only a few percent. 476 00:36:38,916 --> 00:36:54,198 That's pretty good figuring for 2200 years ago. 477 00:36:54,198 --> 00:36:58,135 Then, as now, the Mediterranean was teeming with ships. 478 00:36:58,135 --> 00:37:02,439 Merchantmen, fishing vessels, naval flotillas. 479 00:37:02,439 --> 00:37:08,212 But there were also courageous voyages into the unknown. 480 00:37:08,212 --> 00:37:13,050 400 years before Eratosthenes, Africa was circumnavigated... 481 00:37:13,050 --> 00:37:16,186 ...by a Phoenician fleet in the employ... 482 00:37:16,186 --> 00:37:18,455 ...of the Egyptian pharaoh Necho. 483 00:37:18,455 --> 00:37:19,857 They set sail... 484 00:37:19,857 --> 00:37:24,595 ...probably in boats as frail and open as these... 485 00:37:24,595 --> 00:37:27,998 ...out from the Red Sea, down the east coast of Africa... 486 00:37:27,998 --> 00:37:31,668 ...up into the Atlantic and then back through the Mediterranean. 487 00:37:31,668 --> 00:37:34,571 That epic journey took three years... 488 00:37:34,571 --> 00:37:36,907 ...about as long as it takes Voyager... 489 00:37:36,907 --> 00:37:40,477 ...to journey from Earth to Saturn. 490 00:37:40,477 --> 00:37:43,313 After Eratosthenes, some may have attempted... 491 00:37:43,313 --> 00:37:45,883 ...to circumnavigate the Earth. 492 00:37:45,883 --> 00:37:49,386 But until the time of Magellan, no one succeeded. 493 00:37:49,386 --> 00:37:52,589 What tales of adventure and daring... 494 00:37:52,589 --> 00:37:54,925 ...must earlier have been told... 495 00:37:54,925 --> 00:37:59,463 ...as sailors and navigators, practical men of the world... 496 00:37:59,463 --> 00:38:02,533 ...gambled their lives on the mathematics... 497 00:38:02,533 --> 00:38:12,576 ...of a scientist from ancient Alexandria. 498 00:38:12,576 --> 00:38:16,446 Today, Alexandria shows few traces of its ancient glory... 499 00:38:16,446 --> 00:38:19,983 ...of the days when Eratosthenes walked its broad avenues. 500 00:38:19,983 --> 00:38:24,855 Over the centuries, waves of conquerors converted its palaces and temples... 501 00:38:24,855 --> 00:38:30,961 ...into castles and churches, then into minarets and mosques. 502 00:38:30,961 --> 00:38:35,566 The city was chosen to be the capital of his empire by Alexander the Great... 503 00:38:35,566 --> 00:38:40,070 ...on a winter's afternoon in 331 B.C. 504 00:38:40,070 --> 00:38:43,607 A century later, it had become the greatest city of the world. 505 00:38:43,607 --> 00:38:53,283 Each successive civilization has left its mark. 506 00:38:53,283 --> 00:38:59,223 But what now remains of the marvel city of Alexander's dream? 507 00:38:59,223 --> 00:39:02,326 Alexandria is still a thriving marketplace... 508 00:39:02,326 --> 00:39:12,069 ...still a crossroads for the peoples of the Near East. 509 00:39:12,069 --> 00:39:15,439 But once, it was radiant with self-confidence... 510 00:39:15,439 --> 00:39:24,281 ...certain of its power. 511 00:39:24,281 --> 00:39:26,583 Can you recapture a vanished epoch... 512 00:39:26,583 --> 00:39:38,629 ...from a few broken statues and scraps of ancient manuscripts? 513 00:39:38,629 --> 00:39:42,366 In Alexandria, there was an immense library... 514 00:39:42,366 --> 00:39:45,202 ...and an associated research institute. 515 00:39:45,202 --> 00:39:52,976 And in them worked the finest minds in the ancient world. 516 00:39:52,976 --> 00:39:55,212 (CAN CLUNKS) 517 00:39:55,212 --> 00:40:09,927 (DOOR SQUEAKS) 518 00:40:09,927 --> 00:40:12,562 Of that legendary library... 519 00:40:12,562 --> 00:40:15,332 ...all that survives is this... 520 00:40:15,332 --> 00:40:18,969 ...dank and forgotten cellar. 521 00:40:18,969 --> 00:40:23,106 It's in the library annex, the Serapeum... 522 00:40:23,106 --> 00:40:25,275 ...which was once a temple... 523 00:40:25,275 --> 00:40:28,612 ...but was later reconsecrated to knowledge. 524 00:40:28,612 --> 00:40:32,716 These few moldering shelves... 525 00:40:32,716 --> 00:40:35,352 ...probably once in a basement storage room... 526 00:40:35,352 --> 00:40:38,422 ...are its only physical remains. 527 00:40:38,422 --> 00:40:41,491 But this place was once... 528 00:40:41,491 --> 00:40:44,561 ...the brain and glory... 529 00:40:44,561 --> 00:40:55,706 ...of the greatest city on the planet Earth. 530 00:40:55,706 --> 00:40:58,508 If I could travel back into time... 531 00:40:58,508 --> 00:41:01,945 ...this is the place I would visit. 532 00:41:01,945 --> 00:41:10,520 The Library of Alexandria at its height, 2000 years ago. 533 00:41:10,520 --> 00:41:13,156 Here, in an important sense... 534 00:41:13,156 --> 00:41:24,067 ...began the intellectual adventure which has led us into space. 535 00:41:24,067 --> 00:41:35,112 All the knowledge in the ancient world was once within these marble walls. 536 00:41:35,112 --> 00:41:38,782 In the great hall, there may have been a mural of Alexander... 537 00:41:38,782 --> 00:41:42,219 ...with the crook and flail and ceremonial headdress... 538 00:41:42,219 --> 00:41:48,458 ...of the pharaohs of ancient Egypt. 539 00:41:48,458 --> 00:41:52,162 This library was a citadel of human consciousness... 540 00:41:52,162 --> 00:41:59,603 ...a beacon on our journey to the stars. 541 00:41:59,603 --> 00:42:04,741 It was the first true research institute in the history of the world. 542 00:42:04,741 --> 00:42:06,977 And what did they study? 543 00:42:06,977 --> 00:42:11,114 They studied everything. The entire cosmos. 544 00:42:11,114 --> 00:42:15,719 "Cosmos" is a Greek word for the order of the universe. 545 00:42:15,719 --> 00:42:19,056 In a way, it's the opposite of chaos. 546 00:42:19,056 --> 00:42:24,394 It implies a deep interconnectedness of all things. 547 00:42:24,394 --> 00:42:30,767 The intricate and subtle way that the universe is put together. 548 00:42:30,767 --> 00:42:33,670 Genius flourished here. 549 00:42:33,670 --> 00:42:38,208 In addition to Eratosthenes, there was the astronomer Hipparchus... 550 00:42:38,208 --> 00:42:40,177 ...who mapped the constellation... 551 00:42:40,177 --> 00:42:43,880 ...and established the brightness of the stars. 552 00:42:43,880 --> 00:42:46,149 And there was Euclid... 553 00:42:46,149 --> 00:42:49,186 ...who brilliantly systematized geometry... 554 00:42:49,186 --> 00:42:51,755 ...who told his king, who was struggling... 555 00:42:51,755 --> 00:42:54,591 ...with some difficult problem in mathematics... 556 00:42:54,591 --> 00:42:59,496 ...that there was no royal road to geometry. 557 00:42:59,496 --> 00:43:02,399 There was Dionysius of Thrace, the man who defined... 558 00:43:02,399 --> 00:43:06,069 ...the parts of speech: nouns, verbs and so on... 559 00:43:06,069 --> 00:43:10,207 ...who did for language, in a way, what Euclid did for geometry. 560 00:43:10,207 --> 00:43:14,444 There was Herophilus, a physiologist who identified... 561 00:43:14,444 --> 00:43:18,648 ...the brain rather than the heart as the seat of intelligence. 562 00:43:18,648 --> 00:43:21,551 There was Archimedes, the greatest mechanical genius... 563 00:43:21,551 --> 00:43:23,954 ...until the time of Leonardo da Vinci. 564 00:43:23,954 --> 00:43:28,892 And there was the astronomer Ptolemy, who compiled much of what today is... 565 00:43:28,892 --> 00:43:31,361 ...the pseudoscience of astrology. 566 00:43:31,361 --> 00:43:33,897 His Earth-centered universe... 567 00:43:33,897 --> 00:43:36,766 ...held sway for 1500 years... 568 00:43:36,766 --> 00:43:40,403 ...showing that intellectual brilliance is no guarantee... 569 00:43:40,403 --> 00:43:42,973 ...against being dead wrong. 570 00:43:42,973 --> 00:43:47,177 And among these great men, there was also a great woman. 571 00:43:47,177 --> 00:43:49,579 Her name was Hypatia. 572 00:43:49,579 --> 00:43:52,649 She was a mathematician and an astronomer... 573 00:43:52,649 --> 00:43:54,851 ...the last light of the library... 574 00:43:54,851 --> 00:43:59,956 ...whose martyrdom is bound up with the destruction of this place... 575 00:43:59,956 --> 00:44:21,645 ...seven centuries after it was founded. 576 00:44:21,645 --> 00:44:25,115 Look at this place. 577 00:44:25,115 --> 00:44:28,218 The Greek kings of Egypt who succeeded Alexander... 578 00:44:28,218 --> 00:44:31,755 ...regarded advances in science, literature and medicine... 579 00:44:31,755 --> 00:44:34,224 ...as among the treasures of the empire. 580 00:44:34,224 --> 00:44:38,895 For centuries, they generously supported research and scholarship. 581 00:44:38,895 --> 00:44:46,136 An enlightenment shared by few heads of state, then or now. 582 00:44:46,136 --> 00:44:52,776 (FOUNTAIN GURGLES) 583 00:44:52,776 --> 00:44:56,947 Off this great hall were 10 large research laboratories. 584 00:44:56,947 --> 00:45:01,284 There were fountains and colonnades, botanical gardens... 585 00:45:01,284 --> 00:45:05,855 ...and even a zoo with animals from India and sub-Saharan Africa. 586 00:45:05,855 --> 00:45:12,562 There were dissecting rooms and an astronomical observatory. 587 00:45:12,562 --> 00:45:14,598 But the treasure of the library... 588 00:45:14,598 --> 00:45:18,068 ...consecrated to the god Serapis... 589 00:45:18,068 --> 00:45:21,071 ...built in the city of Alexander... 590 00:45:21,071 --> 00:45:23,106 ...was its collection of books. 591 00:45:23,106 --> 00:45:25,508 The organizers of the library combed... 592 00:45:25,508 --> 00:45:28,945 ...all the cultures and languages of the world for books. 593 00:45:28,945 --> 00:45:32,515 They sent agents abroad to buy up libraries. 594 00:45:32,515 --> 00:45:37,687 Commercial ships docking in Alexandria harbor were searched by the police... 595 00:45:37,687 --> 00:45:40,323 ...not for contraband, but for books. 596 00:45:40,323 --> 00:45:44,094 The scrolls were borrowed, copied and returned to their owners. 597 00:45:44,094 --> 00:45:48,365 Until studied, these scrolls were collected in great stacks... 598 00:45:48,365 --> 00:45:51,935 ...called, "books from the ships." 599 00:45:51,935 --> 00:45:54,571 Accurate numbers are difficult to come by... 600 00:45:54,571 --> 00:45:57,774 ...but it seems that the library contained at its peak... 601 00:45:57,774 --> 00:46:14,424 ...nearly one million scrolls. 602 00:46:14,424 --> 00:46:18,061 The papyrus reed grows in Egypt. 603 00:46:18,061 --> 00:46:20,463 It's the origin of our word for "paper." 604 00:46:20,463 --> 00:46:24,434 Each of those million volumes which once existed in this library... 605 00:46:24,434 --> 00:46:29,839 ...were handwritten on papyrus manuscript scrolls. 606 00:46:29,839 --> 00:46:31,908 What happened to all those books? 607 00:46:31,908 --> 00:46:35,545 The classical civilization that created them disintegrated. 608 00:46:35,545 --> 00:46:38,248 The library itself was destroyed. 609 00:46:38,248 --> 00:46:41,618 Only a small fraction of the works survived. 610 00:46:41,618 --> 00:46:44,954 And as for the rest, we're left only with pathetic... 611 00:46:44,954 --> 00:46:47,457 ...scattered fragments. 612 00:46:47,457 --> 00:46:51,928 But how tantalizing those remaining bits and pieces are. 613 00:46:51,928 --> 00:46:55,799 For example, we know that there once existed here... 614 00:46:55,799 --> 00:47:00,337 ...a book by the astronomer Aristarchus of Samos... 615 00:47:00,337 --> 00:47:04,674 ...who apparently argued that the Earth was one of the planets... 616 00:47:04,674 --> 00:47:08,378 ...that, like the other planets, it orbits the sun... 617 00:47:08,378 --> 00:47:13,116 ...and that the stars are enormously far away. 618 00:47:13,116 --> 00:47:15,785 All absolutely correct. 619 00:47:15,785 --> 00:47:18,621 But we had to wait nearly 2000 years... 620 00:47:18,621 --> 00:47:28,865 ...for these facts to be rediscovered. 621 00:47:28,865 --> 00:47:33,470 The astronomy stacks of the Alexandria Library. 622 00:47:33,470 --> 00:47:35,739 Hipparchus. 623 00:47:35,739 --> 00:47:39,743 Ptolomeus. Here we are. 624 00:47:39,743 --> 00:47:43,646 Aristarchus. 625 00:47:43,646 --> 00:47:45,315 This is the book. 626 00:47:45,315 --> 00:47:48,885 How I'd love to be able to read this book... 627 00:47:48,885 --> 00:47:52,055 ...to know how Aristarchus figured it out. 628 00:47:52,055 --> 00:47:55,892 But it's gone. Utterly and forever. 629 00:47:55,892 --> 00:48:00,463 If we multiply our sense of loss for this work of Aristarchus... 630 00:48:00,463 --> 00:48:02,065 ...by 100,000... 631 00:48:02,065 --> 00:48:04,734 ...we begin to appreciate the grandeur... 632 00:48:04,734 --> 00:48:07,804 ...of the achievement of classical civilization... 633 00:48:07,804 --> 00:48:14,177 ...and the tragedy of its destruction. 634 00:48:14,177 --> 00:48:18,915 We have far surpassed the science known to the ancient world... 635 00:48:18,915 --> 00:48:22,752 ...but there are irreparable gaps in our historical knowledge. 636 00:48:22,752 --> 00:48:26,322 Imagine what mysteries of the past could be solved... 637 00:48:26,322 --> 00:48:28,958 ...with a borrower's card to this library. 638 00:48:28,958 --> 00:48:33,396 For example, we know of a three-volume history of the world... 639 00:48:33,396 --> 00:48:38,101 ...now lost, written by a Babylonian priest named Berossus. 640 00:48:38,101 --> 00:48:41,938 Volume I dealt with the interval from the creation of the world... 641 00:48:41,938 --> 00:48:43,306 ...to the Great Flood. 642 00:48:43,306 --> 00:48:47,577 A period that he took to be 432,000 years... 643 00:48:47,577 --> 00:48:51,514 ...or about 100 times longer than the Old Testament chronology. 644 00:48:51,514 --> 00:48:56,519 What wonders were in the books of Berossus! 645 00:48:56,519 --> 00:49:00,757 But why have I brought you across 2000 years... 646 00:49:00,757 --> 00:49:03,760 ...to the Library of Alexandria? 647 00:49:03,760 --> 00:49:07,263 Because this was when and where we humans... 648 00:49:07,263 --> 00:49:11,568 ...first collected seriously and systematically... 649 00:49:11,568 --> 00:49:13,803 ...the knowledge of the world. 650 00:49:13,803 --> 00:49:16,506 This is the Earth as Eratosthenes knew it. 651 00:49:16,506 --> 00:49:19,976 A tiny, spherical world, afloat... 652 00:49:19,976 --> 00:49:23,446 ...in an immensity of space and time. 653 00:49:23,446 --> 00:49:26,349 We were, at long last, beginning to find... 654 00:49:26,349 --> 00:49:30,053 ...our true bearings in the cosmos. 655 00:49:30,053 --> 00:49:32,121 The scientists of antiquity... 656 00:49:32,121 --> 00:49:35,925 ...took the first and most important steps in that direction... 657 00:49:35,925 --> 00:49:38,995 ...before their civilization fell apart. 658 00:49:38,995 --> 00:49:42,065 But after the Dark Ages, it was by and large... 659 00:49:42,065 --> 00:49:46,202 ...the rediscovery of the works of these scholars done here... 660 00:49:46,202 --> 00:49:48,605 ...that made the Renaissance possible... 661 00:49:48,605 --> 00:49:51,875 ...and thereby powerfully influenced our own culture. 662 00:49:51,875 --> 00:49:55,311 When, in the 15th century, Europe was at last ready... 663 00:49:55,311 --> 00:49:58,314 ...to awaken from its long sleep... 664 00:49:58,314 --> 00:50:02,785 ...it picked up some of the tools, the books and the concepts... 665 00:50:02,785 --> 00:50:12,262 ...laid down here more than a thousand years before. 666 00:50:12,262 --> 00:50:16,366 By 1600, the long-forgotten ideas of Aristarchus... 667 00:50:16,366 --> 00:50:18,668 ...had been rediscovered. 668 00:50:18,668 --> 00:50:22,138 Johannes Kepler constructed elaborate models... 669 00:50:22,138 --> 00:50:25,241 ...to understand the motion and arrangement of the planets... 670 00:50:25,241 --> 00:50:32,015 ...the clockwork of the heavens. 671 00:50:32,015 --> 00:50:46,563 And at night, he dreamt of traveling to the moon. 672 00:50:46,563 --> 00:50:48,965 His principal scientific tools were... 673 00:50:48,965 --> 00:50:51,968 ...the mathematics of the Alexandrian Library... 674 00:50:51,968 --> 00:50:54,604 ...and an unswerving respect for the facts... 675 00:50:54,604 --> 00:51:01,444 ...however disquieting they might be. 676 00:51:01,444 --> 00:51:05,081 His story, and the story of the scientists who came after him... 677 00:51:05,081 --> 00:51:09,886 ...are also part of our voyage. 678 00:51:09,886 --> 00:51:13,056 Seventy years later, the sun-centered universe... 679 00:51:13,056 --> 00:51:14,857 ...of Aristarchus and Copernicus... 680 00:51:14,857 --> 00:51:18,928 ...was widely accepted in the Europe of the Enlightenment. 681 00:51:18,928 --> 00:51:22,565 The idea arose that the planets were worlds... 682 00:51:22,565 --> 00:51:24,400 ...governed by laws of nature... 683 00:51:24,400 --> 00:51:28,838 ...and scientific speculation turned to the motions of the stars. 684 00:51:28,838 --> 00:51:31,674 The clockwork in the heavens was imitated... 685 00:51:31,674 --> 00:51:34,043 ...by the watchmakers of Earth. 686 00:51:34,043 --> 00:51:37,747 Precise timekeeping permitted great sailing ship voyages... 687 00:51:37,747 --> 00:51:40,483 ...of exploration and discovery... 688 00:51:40,483 --> 00:51:44,487 ...which bound up the Earth. 689 00:51:44,487 --> 00:51:47,023 This was a time when free inquiry... 690 00:51:47,023 --> 00:51:49,192 ...was valued once again. 691 00:51:49,192 --> 00:51:55,898 (SPEAKING IN FOREIGN LANGUAGE) 692 00:51:55,898 --> 00:51:59,502 250 years later, the Earth was all explored. 693 00:51:59,502 --> 00:52:03,406 New adventurers now looked to the planets and the stars. 694 00:52:03,406 --> 00:52:07,276 The galaxies were recognized as great aggregates of stars... 695 00:52:07,276 --> 00:52:12,115 ...island universes millions of light years away. 696 00:52:12,115 --> 00:52:15,451 In the 1920s, astronomers had begun to measure... 697 00:52:15,451 --> 00:52:22,959 ...the speeds of distant galaxies. 698 00:52:22,959 --> 00:52:24,127 ASTRONOMER 1: What time is it? 699 00:52:24,127 --> 00:52:26,262 7:15. 700 00:52:26,262 --> 00:52:28,398 ASTRONOMER 1: Lights off, please. 701 00:52:28,398 --> 00:52:33,236 They found that the galaxies were flying away from one another. 702 00:52:33,236 --> 00:52:35,338 To the astonishment of everyone... 703 00:52:35,338 --> 00:52:44,380 ...the entire universe was expanding. 704 00:52:44,380 --> 00:52:51,621 We had begun to plumb the true depths of time and space. 705 00:52:51,621 --> 00:52:54,524 The long, collective enterprise of science... 706 00:52:54,524 --> 00:52:59,028 ...has revealed a universe some 15 billion years old. 707 00:52:59,028 --> 00:53:02,231 The time since the explosive birth of the cosmos... 708 00:53:02,231 --> 00:53:03,466 ...the big bang. 709 00:53:03,466 --> 00:53:03,833 The current estimates for the age of the universe range from 12 to 15 billion years. 710 00:53:03,833 --> 00:53:09,972 (THUNDER CRASHES) 711 00:53:09,972 --> 00:53:14,210 The cosmic calendar compresses the local history of the universe... 712 00:53:14,210 --> 00:53:16,145 ...into a single year. 713 00:53:16,145 --> 00:53:18,915 If the universe began on January 1st... 714 00:53:18,915 --> 00:53:23,052 ...it was not until May that the Milky Way formed. 715 00:53:23,052 --> 00:53:26,022 Other planetary systems may have appeared... 716 00:53:26,022 --> 00:53:29,192 ...in June, July and August... 717 00:53:29,192 --> 00:53:32,128 ...but our sun and Earth, not until mid-September. 718 00:53:32,128 --> 00:53:35,364 Life arose soon after. 719 00:53:35,364 --> 00:53:39,635 Everything humans have ever done occurred in that bright speck... 720 00:53:39,635 --> 00:53:45,341 ...at the lower right of the cosmic calendar. 721 00:53:45,341 --> 00:53:47,543 The big bang is at upper left... 722 00:53:47,543 --> 00:53:50,513 ...in the first second of January 1st. 723 00:53:50,513 --> 00:53:54,417 Fifteen billion years later is our present time... 724 00:53:54,417 --> 00:54:02,759 ...the last second of December 31st. 725 00:54:02,759 --> 00:54:06,195 Every month is 1ΕΊ billion years long. 726 00:54:06,195 --> 00:54:09,298 Each day represents 40 million years. 727 00:54:09,298 --> 00:54:13,236 Each second stands for some 500 years of our history. 728 00:54:13,236 --> 00:54:22,845 The blinking of an eye in the drama of cosmic time. 729 00:54:22,845 --> 00:54:27,517 At this scale, the cosmic calendar is the size of a football field... 730 00:54:27,517 --> 00:54:30,887 ...but all of human history would occupy an area... 731 00:54:30,887 --> 00:54:32,722 ...the size of my hand. 732 00:54:32,722 --> 00:54:36,392 We're just beginning to trace the long and tortuous path... 733 00:54:36,392 --> 00:54:39,328 ...which began with the primeval fireball... 734 00:54:39,328 --> 00:54:42,231 ...and led to the condensation of matter: 735 00:54:42,231 --> 00:54:45,067 Gas, dust, stars, galaxies, and... 736 00:54:45,067 --> 00:54:47,637 ...at least in our little nook of the universe... 737 00:54:47,637 --> 00:54:52,141 ...planets, life, intelligence and inquisitive men and women. 738 00:54:52,141 --> 00:54:53,943 We've emerged so recently... 739 00:54:53,943 --> 00:54:57,013 ...that the familiar events of our recorded history... 740 00:54:57,013 --> 00:55:01,450 ...occupy only the last seconds of the last minute of December 31st. 741 00:55:01,450 --> 00:55:05,288 But some critical events for the human species began much earlier... 742 00:55:05,288 --> 00:55:08,324 ...minutes earlier. 743 00:55:08,324 --> 00:55:11,928 So we change our scale from months to minutes. 744 00:55:11,928 --> 00:55:15,298 Down here, the first humans made their debut... 745 00:55:15,298 --> 00:55:21,671 ...around 10:30 p.m. on December 31st. 746 00:55:21,671 --> 00:55:24,207 And with the passing of every cosmic minute... 747 00:55:24,207 --> 00:55:26,475 ...each minute 30,000 years long... 748 00:55:26,475 --> 00:55:29,011 ...we began the arduous journey towards understanding... 749 00:55:29,011 --> 00:55:34,517 ...where we live and who we are. 750 00:55:34,517 --> 00:55:36,819 11:46... 751 00:55:36,819 --> 00:55:39,655 ...only 14 minutes ago... 752 00:55:39,655 --> 00:55:43,359 ...humans have tamed fire. 753 00:55:43,359 --> 00:55:48,364 11:59:20, the evening of the last day of the cosmic year... 754 00:55:48,364 --> 00:55:52,401 ...the 11th hour, the 59th minute, the 20th second... 755 00:55:52,401 --> 00:55:55,471 ...the domestication of plants and animals begins: 756 00:55:55,471 --> 00:56:01,244 An application of the human talent... 757 00:56:01,244 --> 00:56:10,186 ...for making tools. 758 00:56:10,186 --> 00:56:14,891 11:59:35, settled agricultural communities... 759 00:56:14,891 --> 00:56:18,561 ...evolved into the first cities. 760 00:56:18,561 --> 00:56:22,865 We humans appear on the comic calendar so recently... 761 00:56:22,865 --> 00:56:25,468 ...that our recorded history occupies only... 762 00:56:25,468 --> 00:56:31,140 ...the last few seconds of the last minute of December 31 st. 763 00:56:31,140 --> 00:56:36,112 In the vast ocean of time which this calendar represents... 764 00:56:36,112 --> 00:56:41,651 ...all our memories are confined... 765 00:56:41,651 --> 00:56:44,253 ...to this small square. 766 00:56:44,253 --> 00:56:49,558 Every person we've ever heard of lived somewhere in there. 767 00:56:49,558 --> 00:56:54,931 All those kings and battles, migrations and inventions, wars and loves. 768 00:56:54,931 --> 00:56:56,899 Everything in the history books... 769 00:56:56,899 --> 00:56:59,702 ...happens here... 770 00:56:59,702 --> 00:57:08,377 ...in the last 10 seconds of the cosmic calendar. 771 00:57:08,377 --> 00:57:11,080 We on Earth have just awakened... 772 00:57:11,080 --> 00:57:14,083 ...to the great oceans of space and time... 773 00:57:14,083 --> 00:57:17,353 ...from which we have emerged. 774 00:57:17,353 --> 00:57:19,121 We are the legacy... 775 00:57:19,121 --> 00:57:23,259 ...of 15 billion years of cosmic evolution. 776 00:57:23,259 --> 00:57:25,261 We have a choice: 777 00:57:25,261 --> 00:57:28,965 We can enhance life and come to know the universe that made us... 778 00:57:28,965 --> 00:57:32,401 ...or we can squander our 15 billion-year heritage... 779 00:57:32,401 --> 00:57:36,572 ...in meaningless self-destruction. 780 00:57:36,572 --> 00:57:39,976 What happens in the first second of the next cosmic year... 781 00:57:39,976 --> 00:57:43,346 ...depends on what we do, here and now... 782 00:57:43,346 --> 00:57:45,348 ...with our intelligence... 783 00:57:45,348 --> 99:59:59,999 ...and our knowledge of the cosmos.