1 00:00:03,104 --> 00:00:07,041 TYSON: In our galaxy, there may be ships of other worlds 2 00:00:07,075 --> 00:00:11,312 that dare to venture into the cosmic deep. 3 00:00:13,214 --> 00:00:15,883 Perhaps they travel from star to star, 4 00:00:15,916 --> 00:00:19,520 searching for worlds where life has taken hold. 5 00:00:19,553 --> 00:00:23,023 To get a closer look at the emergent properties of life 6 00:00:23,057 --> 00:00:25,993 that even they can't predict. 7 00:00:26,960 --> 00:00:31,699 This particular vessel is on just such a survey mission. 8 00:00:33,701 --> 00:00:39,207 Who, scanning this world, would have pronounced it a fit nursery for life? 9 00:00:40,741 --> 00:00:44,512 What wild optimist could have foreseen that peonies 10 00:00:44,545 --> 00:00:49,049 and eagles would one day spring from this hell hole? 11 00:00:52,720 --> 00:00:56,357 In its infancy, four billion years ago, 12 00:00:56,390 --> 00:01:00,761 Earth held little apparent promise. 13 00:01:01,595 --> 00:01:06,033 Now, Venus, that's more like it. 14 00:01:06,066 --> 00:01:11,939 Back then, it may have had oceans and land and possibly life. 15 00:01:16,410 --> 00:01:21,215 This long-ago epoch was Venus' moment to flourish. 16 00:01:21,249 --> 00:01:24,852 Its time in the habitable zone. 17 00:01:24,885 --> 00:01:27,688 For any world, that's a period when its relationship to 18 00:01:27,721 --> 00:01:32,226 its star means that it's not too hot and not too cold. 19 00:01:33,427 --> 00:01:38,632 It's a time in a world's existence when it can foster and sustain life. 20 00:01:40,534 --> 00:01:44,238 But the grace of the habitable zone is a fleeting thing 21 00:01:44,272 --> 00:01:48,609 and, for no world, lasts forever. 22 00:01:51,912 --> 00:01:55,048 We reside in our star's habitable zone, 23 00:01:55,082 --> 00:01:59,787 but it is moving outwards at the rate of about three feet per year. 24 00:01:59,820 --> 00:02:04,592 Earth has already passed through 70% of its most hospitable time, 25 00:02:04,625 --> 00:02:06,660 but no need to worry, 26 00:02:06,694 --> 00:02:09,763 that stills leaves us hundreds of millions of years 27 00:02:09,797 --> 00:02:13,734 to plan and execute our exit strategy. 28 00:02:13,767 --> 00:02:17,705 Where will we go when the sun's grace leave us behind 29 00:02:17,738 --> 00:02:22,976 for other worlds and Earth is no longer a garden for life? 30 00:02:23,477 --> 00:02:26,547 Will our species have set sail for distant islands in 31 00:02:26,580 --> 00:02:29,983 the vast ocean of the Milky Way? 32 00:02:32,152 --> 00:02:38,125 (theme music plays). 33 00:02:56,710 --> 00:03:03,217 * 34 00:03:23,837 --> 00:03:30,644 * 35 00:03:34,782 --> 00:03:40,220 (waves crashing). 36 00:03:44,725 --> 00:03:47,728 TYSON: There is no refuge from change in the cosmos. 37 00:03:47,761 --> 00:03:51,632 No safe place to hide for more than a few hundred million years. 38 00:03:52,600 --> 00:03:57,571 Someday, all of this will surrender to the churning cycles of birth, 39 00:03:57,605 --> 00:04:02,209 destruction and rebirth mandated by the laws of nature. 40 00:04:03,010 --> 00:04:06,514 The universe evolves beautiful things then smashes 41 00:04:06,547 --> 00:04:10,784 them to bits before making new ones out of the shattered pieces. 42 00:04:10,818 --> 00:04:14,187 Any species that wants to survive long term on any 43 00:04:14,221 --> 00:04:17,691 possible world, will have to learn how to engineer 44 00:04:17,725 --> 00:04:21,962 interplanetary and ultimately, interstellar mass transit. 45 00:04:25,533 --> 00:04:28,035 How do we know this? 46 00:04:28,068 --> 00:04:31,071 The little we've learned about the universe allows us 47 00:04:31,104 --> 00:04:33,407 glimpses of the future. 48 00:04:33,441 --> 00:04:36,176 I'm not talking about the near-term where climate change 49 00:04:36,209 --> 00:04:40,247 caused by human activity poses a danger to our civilization. 50 00:04:40,280 --> 00:04:43,551 If we want to endure for thousands, 51 00:04:43,584 --> 00:04:46,887 millions even billions of years, 52 00:04:46,920 --> 00:04:49,390 we'll have to stop dumping all that carbon dioxide into 53 00:04:49,423 --> 00:04:52,626 the atmosphere, right now. 54 00:04:52,660 --> 00:04:54,895 But I'm gonna give us the benefit of the doubt 55 00:04:54,928 --> 00:04:57,898 and take the long view. 56 00:05:00,434 --> 00:05:02,703 The sun is aging. 57 00:05:02,736 --> 00:05:04,972 Just like the rest of us. 58 00:05:05,005 --> 00:05:09,943 Someday, it will exhaust the hydrogen fuel at its core. 59 00:05:16,650 --> 00:05:18,819 Five or six billion years from now, 60 00:05:18,852 --> 00:05:23,323 the zone of hydrogen fusion will slowly migrate outward, 61 00:05:23,357 --> 00:05:26,960 an expanding shell of thermonuclear reactions. 62 00:05:26,994 --> 00:05:31,031 Until the temperatures are less than about 10 million degrees. 63 00:05:39,306 --> 00:05:43,977 It will go from being a yellow dwarf to a red giant. 64 00:05:44,812 --> 00:05:48,449 Its gravitational hold on Venus and Earth will diminish 65 00:05:48,482 --> 00:05:51,952 allowing them to migrate to a safer distance, 66 00:05:51,985 --> 00:05:54,888 for a little while. 67 00:05:54,922 --> 00:05:58,626 This red giant sun, ruddy and bloated, 68 00:05:58,659 --> 00:06:01,929 will envelop and devour the planet Mercury. 69 00:06:08,168 --> 00:06:11,405 The grace of the habitable zone will be moving outward, 70 00:06:11,439 --> 00:06:14,374 farther and faster. 71 00:06:15,008 --> 00:06:18,512 By now, the intense light and heat of the sun's expansion 72 00:06:18,546 --> 00:06:22,683 will reach all the way out to the Jupiter system. 73 00:06:23,083 --> 00:06:25,486 Its clouds of ammonia and water will escape and 74 00:06:25,519 --> 00:06:29,256 be lost to space as vapor. 75 00:06:31,224 --> 00:06:34,662 And for the first time, the more dowdy, hidden layers 76 00:06:34,695 --> 00:06:39,933 down beneath Jupiter's gaudy upper atmosphere will be exposed. 77 00:06:44,738 --> 00:06:50,077 Could we make a home on one of Jupiter's frozen moons? 78 00:06:50,611 --> 00:06:54,948 The thick layers of ice encasing Europa and Callisto will defrost, 79 00:06:54,982 --> 00:06:59,086 exposing the liquid oceans beneath to harsh sunlight, 80 00:06:59,119 --> 00:07:02,756 thousands of times stronger than before. 81 00:07:02,790 --> 00:07:06,960 This will liberate large amounts of water vapor, 82 00:07:06,994 --> 00:07:10,464 starting a runaway greenhouse effect. 83 00:07:11,465 --> 00:07:16,970 Ganymede's once thin atmosphere will become steamy and dense. 84 00:07:22,442 --> 00:07:25,412 If life was swimming in those oceans all along, 85 00:07:25,445 --> 00:07:28,882 here's a new chance to flourish and evolve. 86 00:07:28,916 --> 00:07:32,052 Then Ganymede will belong to those beings. 87 00:07:32,085 --> 00:07:35,122 It's just as well, because we'll want our next home 88 00:07:35,155 --> 00:07:39,092 to be at a safer distance from the sun. 89 00:07:40,961 --> 00:07:43,430 Solar evolution is inevitable, 90 00:07:43,463 --> 00:07:46,634 but we have a billion years to go house hunting. 91 00:07:46,667 --> 00:07:49,803 Plenty of time to seek those worlds in the cosmos 92 00:07:49,837 --> 00:07:53,440 that could become our new homes. 93 00:07:54,775 --> 00:07:59,279 Saturn, what has the sun done to you? 94 00:07:59,312 --> 00:08:03,784 She's stolen your glory, your rings. 95 00:08:06,019 --> 00:08:09,189 And Titan, she's robbed you of your atmosphere. 96 00:08:13,594 --> 00:08:15,896 (thunder). 97 00:08:15,929 --> 00:08:17,297 Hey. 98 00:08:17,330 --> 00:08:20,433 We're running out of possible worlds here. 99 00:08:24,538 --> 00:08:27,908 Just in time, Neptune's moon, Triton, 100 00:08:27,941 --> 00:08:31,779 a world named for the son of the Roman God, Neptune. 101 00:08:31,812 --> 00:08:36,016 First known to the Greeks as Poseidon, the God of the Sea. 102 00:08:51,599 --> 00:08:55,803 No one's named this ocean yet, it only began to exist when 103 00:08:55,836 --> 00:08:59,306 the heat of the red giant sun melted the ammonia and 104 00:08:59,339 --> 00:09:03,443 water ices of this once frigid moon. 105 00:09:03,476 --> 00:09:07,948 Our distant descendants will live to different rhythms than we do. 106 00:09:07,981 --> 00:09:12,820 A day on Triton will be 144 hours long. 107 00:09:12,853 --> 00:09:14,622 And the winters will be brutal. 108 00:09:14,655 --> 00:09:17,691 They'll be nearly 50 years long. 109 00:09:17,725 --> 00:09:21,028 But still, the Triton of a few billion years from now could 110 00:09:21,061 --> 00:09:23,363 be a great home for us. 111 00:09:23,396 --> 00:09:24,832 It's got everything, 112 00:09:24,865 --> 00:09:27,134 an atmosphere, water oceans, 113 00:09:27,167 --> 00:09:30,671 the chemical building blocks would make life possible. 114 00:09:30,704 --> 00:09:35,676 Okay, it's chilly, but not much worse than upstate New York in January. 115 00:09:35,709 --> 00:09:39,747 And that means, great skiing all year round. 116 00:09:45,953 --> 00:09:49,957 But one day, the sun will exhaust itself completely and 117 00:09:49,990 --> 00:09:54,762 the fleeting grace of the habitable zone will end here, too. 118 00:09:54,795 --> 00:09:57,765 When the sun's torrid red giant phase is over, 119 00:09:57,798 --> 00:10:00,701 it will strip itself naked, 120 00:10:00,734 --> 00:10:04,304 revealing the small white dwarf beneath. 121 00:10:04,905 --> 00:10:09,142 A star without even enough energy left to warm her surviving children. 122 00:10:10,143 --> 00:10:14,147 The moons of the outer Solar System. 123 00:10:21,922 --> 00:10:25,392 So, if we're looking for a long lease on a new home. 124 00:10:25,425 --> 00:10:28,461 Say, more than just a couple hundred million years, 125 00:10:28,495 --> 00:10:31,598 we'd have to travel even farther out. 126 00:10:31,631 --> 00:10:34,467 We'll have to leave our Solar System and brave the 127 00:10:34,501 --> 00:10:37,938 vast bottomless ocean of interstellar space. 128 00:10:37,971 --> 00:10:40,207 I know what you're thinking, 129 00:10:40,240 --> 00:10:43,510 "are we to venture to the distant stars?" 130 00:10:43,543 --> 00:10:46,646 We once made a few baby steps to the moon before we lost 131 00:10:46,680 --> 00:10:50,751 our will and scurried back to the safety of our mother. 132 00:10:50,784 --> 00:10:55,388 What makes us think we could survive a voyage between the stars? 133 00:10:55,422 --> 00:11:00,060 The nearest of which is 100 million times farther than our moon. 134 00:11:00,093 --> 00:11:03,997 Wouldn't our tiny ships be swallowed up by the great unknown? 135 00:11:04,031 --> 00:11:06,399 I think we can do it. 136 00:11:06,433 --> 00:11:08,668 Why? 137 00:11:08,702 --> 00:11:11,471 Because we've done it before. 138 00:11:25,318 --> 00:11:29,122 TYSON: We dream of sailing among the island worlds of the Milky Way, 139 00:11:29,156 --> 00:11:32,292 catching photons with our sails. 140 00:11:32,325 --> 00:11:37,364 Daring to go tetherless beyond the point of no return. 141 00:11:39,967 --> 00:11:42,936 We've passed this way before. 142 00:11:42,970 --> 00:11:46,673 Once, there was a people who chose the unknown. 143 00:11:46,706 --> 00:11:50,577 They risked everything to go forth on uncharted seas 144 00:11:50,610 --> 00:11:53,446 and their courage was rewarded. 145 00:11:53,480 --> 00:11:56,483 They found paradise. 146 00:11:56,516 --> 00:12:00,087 I want to tell you their story. 147 00:12:02,655 --> 00:12:07,828 (singing). 148 00:12:07,861 --> 00:12:09,930 We call these people, the Lapita. 149 00:12:09,963 --> 00:12:12,132 But, that was never their name. 150 00:12:12,165 --> 00:12:14,701 It was just the result of a misunderstanding made 151 00:12:14,734 --> 00:12:17,637 decades ago when we first began to discover the 152 00:12:17,670 --> 00:12:20,908 broken shards of their pottery. 153 00:12:20,941 --> 00:12:25,913 To me, they're not the Lapita, they are the Voyagers. 154 00:12:25,946 --> 00:12:29,316 A name far more worthy of them. 155 00:12:30,984 --> 00:12:32,853 About 10,000 years ago, 156 00:12:32,886 --> 00:12:36,089 when the population of settlements in Southern China began to swell, 157 00:12:36,123 --> 00:12:40,027 there were those who chose to pioneer the frontier, 158 00:12:40,060 --> 00:12:43,630 farther south to what is now Taiwan. 159 00:12:45,933 --> 00:12:48,501 And our voyagers settled there, 160 00:12:48,535 --> 00:12:50,770 happily for thousands of years, 161 00:12:50,804 --> 00:12:55,275 until the place began to get too crowded again. 162 00:12:56,776 --> 00:12:58,912 Just as we, of this planet, 163 00:12:58,946 --> 00:13:02,115 came of age in a kind of cosmic quarantine. 164 00:13:02,149 --> 00:13:04,384 Cut off from any hope of knowing about, 165 00:13:04,417 --> 00:13:07,855 much less reaching the other worlds of the cosmos. 166 00:13:07,888 --> 00:13:12,792 Our distant ancestors were prisoners of the land. 167 00:13:13,861 --> 00:13:15,929 If you wanted to travel a great distance, 168 00:13:15,963 --> 00:13:17,630 you had to walk there. 169 00:13:17,664 --> 00:13:19,699 And if you walked as far as you could, 170 00:13:19,732 --> 00:13:22,435 you would be hemmed in at the water's edge. 171 00:13:22,469 --> 00:13:26,073 This was before the age of the great sea-faring civilizations. 172 00:13:26,106 --> 00:13:29,943 The Phoenicians of the Middle-East and the Minoans of Crete. 173 00:13:29,977 --> 00:13:33,680 And for most of their history, they hugged the shore. 174 00:13:33,713 --> 00:13:38,485 Their fishing and trading expeditions were careful to keep land in sight. 175 00:13:43,356 --> 00:13:49,096 For our ancestors, this was the edge of the cosmic ocean. 176 00:13:52,465 --> 00:13:55,435 We do not know what first inspired the voyagers to 177 00:13:55,468 --> 00:13:58,471 attempt the seemingly impossible. 178 00:13:58,505 --> 00:14:01,441 Could they no longer trust the Earth? 179 00:14:01,474 --> 00:14:04,912 (rumbling). 180 00:14:04,945 --> 00:14:07,948 They were living on a tectonic plate where earthquakes 181 00:14:07,981 --> 00:14:10,951 and volcanic eruptions were common. 182 00:14:10,984 --> 00:14:15,355 Or did hostile neighbors there make life intolerable for them? 183 00:14:17,690 --> 00:14:21,328 Did a change in climate threaten their livelihood? 184 00:14:22,262 --> 00:14:25,498 Were their new population pressures? 185 00:14:25,532 --> 00:14:29,036 Did they begin to exhaust the resources of their island 186 00:14:29,069 --> 00:14:32,906 by overhunting and overfishing? 187 00:14:34,341 --> 00:14:37,810 Or was it simply something innately human in them that 188 00:14:37,844 --> 00:14:41,181 made them want to know what was out there? 189 00:14:41,214 --> 00:14:43,483 To reach for the mysterious distance, 190 00:14:43,516 --> 00:14:46,753 no matter how dangerous that might be? 191 00:14:46,786 --> 00:14:49,923 Whatever their motives, over time, 192 00:14:49,957 --> 00:14:53,126 they conquered their fear. 193 00:14:53,160 --> 00:14:57,864 And made preparations to venture where no one had gone before. 194 00:14:58,865 --> 00:15:04,938 (speaking in native language). 195 00:15:15,415 --> 00:15:22,255 * 196 00:15:26,093 --> 00:15:29,229 (clucking, oinking). 197 00:15:36,369 --> 00:15:39,172 (chirping). 198 00:15:43,410 --> 00:15:50,150 * 199 00:16:15,475 --> 00:16:22,315 * 200 00:16:41,901 --> 00:16:44,504 (chirping). 201 00:16:57,417 --> 00:17:03,523 (rain). 202 00:17:05,892 --> 00:17:10,863 (thunder). 203 00:17:15,868 --> 00:17:21,074 (waves crashing). 204 00:17:23,943 --> 00:17:30,817 * 205 00:17:38,858 --> 00:17:41,861 (chirping). 206 00:18:24,537 --> 00:18:27,240 TYSON: The voyagers used the careful observations of their 207 00:18:27,274 --> 00:18:30,943 ancestors over generations to develop navigational 208 00:18:30,977 --> 00:18:34,881 techniques that are still viable today. 209 00:18:34,914 --> 00:18:40,220 The seasonal migratory flight patterns of the birds was their GPS. 210 00:18:40,253 --> 00:18:42,789 They also brought high flying frigatebirds with them, 211 00:18:42,822 --> 00:18:45,358 releasing them at the proper time to find the shortest 212 00:18:45,392 --> 00:18:48,561 distance to the nearest land. 213 00:18:48,595 --> 00:18:50,963 They could read water, feeling the ocean currents in their 214 00:18:50,997 --> 00:18:54,967 fingertips and the messages written in the clouds. 215 00:18:55,001 --> 00:19:00,673 These voyagers were scientists and all of nature was their laboratory. 216 00:19:07,480 --> 00:19:11,418 (speaking in native language). 217 00:19:27,166 --> 00:19:29,336 (shouts). 218 00:19:36,376 --> 00:19:42,882 * 219 00:19:42,915 --> 00:19:47,220 TYSON: The Philippine Islands was where they settled first. 220 00:19:50,122 --> 00:19:53,293 After lingering there for 1,000 years, 221 00:19:53,326 --> 00:19:56,896 they were ready to set sail again. 222 00:19:58,030 --> 00:20:00,833 New generations of voyagers, Polynesians, 223 00:20:00,867 --> 00:20:04,871 mounted successful missions of exploration to Indonesia. 224 00:20:04,904 --> 00:20:08,541 The Melanesian Islands, Vanuatu, 225 00:20:08,575 --> 00:20:14,213 Fiji, Samoa and onto the Marquesas. 226 00:20:15,248 --> 00:20:19,218 And then, to the most isolated island group on Earth, 227 00:20:19,252 --> 00:20:22,389 the Hawaiian Islands. 228 00:20:22,422 --> 00:20:29,095 Tahiti, Tonga, New Zealand, Pitcairn and Easter Island. 229 00:20:30,196 --> 00:20:35,067 Their empire of water covered nearly 20 million square miles of sea. 230 00:20:35,101 --> 00:20:38,070 And they accomplished this without a single nail 231 00:20:38,104 --> 00:20:41,040 or metal tool of any kind. 232 00:20:41,073 --> 00:20:43,910 As contact between the islands became less frequent, 233 00:20:43,943 --> 00:20:47,046 the language the Polynesians brought with them evolved into 234 00:20:47,079 --> 00:20:49,749 different tongues in isolation. 235 00:20:49,782 --> 00:20:52,919 Many words changed, but one word remained the same 236 00:20:52,952 --> 00:20:58,491 in all the languages of the wide pacific: "Lyar," 237 00:20:58,525 --> 00:21:02,094 the world for "sail." 238 00:21:16,075 --> 00:21:22,715 * 239 00:21:28,287 --> 00:21:31,791 Where are we bound for next? 240 00:21:33,259 --> 00:21:37,664 To that place where you can read the book of worlds. 241 00:21:57,817 --> 00:22:00,920 TYSON: The ship of the imagination is on a mission. 242 00:22:00,953 --> 00:22:03,823 Not to any particular world, 243 00:22:03,856 --> 00:22:07,994 but to an empty space in the interstellar ocean. 244 00:22:08,595 --> 00:22:10,262 Why there? 245 00:22:10,296 --> 00:22:11,931 Come with me. 246 00:22:11,964 --> 00:22:16,102 We're headed to a place 50 billion miles from our sun. 247 00:22:16,135 --> 00:22:18,938 What I'm about to show you is a gift of thousands 248 00:22:18,971 --> 00:22:21,408 of generations of searchers. 249 00:22:21,441 --> 00:22:26,278 We've been studying light for millennia and gravity for centuries. 250 00:22:26,312 --> 00:22:29,181 Among Einstein's many insights was an understanding 251 00:22:29,215 --> 00:22:32,419 of how one could affect the other. 252 00:22:32,452 --> 00:22:35,588 The way gravity bends light makes it possible to turn 253 00:22:35,622 --> 00:22:37,924 any star, including our own, 254 00:22:37,957 --> 00:22:41,628 into a kind of lens for a cosmic telescope. 255 00:22:41,661 --> 00:22:44,631 One 50 billion miles long. 256 00:22:44,664 --> 00:22:48,000 Our most powerful space-based telescopes of the present day 257 00:22:48,034 --> 00:22:52,238 can only see the worlds of other suns as mere dots. 258 00:22:52,271 --> 00:22:56,208 A cosmic telescope could give us detailed images of 259 00:22:56,242 --> 00:23:00,179 the mountains, oceans, glaciers and who knows? 260 00:23:00,212 --> 00:23:03,616 Maybe even the cities of these worlds. 261 00:23:10,289 --> 00:23:14,627 This is the cosmic telescope's detector array. 262 00:23:14,661 --> 00:23:18,698 Collecting the light bouncing off a distant world. 263 00:23:18,731 --> 00:23:23,470 It then sends a signal back to Earth, becoming, in effect, 264 00:23:23,503 --> 00:23:27,273 the telescope's eye piece. 265 00:23:27,907 --> 00:23:30,510 See that brightest star in the sky? 266 00:23:30,543 --> 00:23:32,612 That's our sun. 267 00:23:32,645 --> 00:23:36,215 And the lens of this telescope. 268 00:23:36,248 --> 00:23:39,085 So, how can a star, which you can't see through, 269 00:23:39,118 --> 00:23:42,822 be turned into a lens? 270 00:23:42,855 --> 00:23:45,692 When all the rays of light from a distant planet pass 271 00:23:45,725 --> 00:23:48,728 very close to the sun, the sun's gravity bends 272 00:23:48,761 --> 00:23:51,831 those rays ever so slightly. 273 00:23:51,864 --> 00:23:55,034 Where they converge in space is called the focal point 274 00:23:55,067 --> 00:23:59,539 because that's where the object you're looking at comes into focus. 275 00:24:02,241 --> 00:24:06,913 So, what can you see through a 50 billion mile long telescope? 276 00:24:06,946 --> 00:24:10,182 Virtually anything you want. 277 00:24:10,216 --> 00:24:14,821 Galileo's best telescope could magnify an image 30 times, 278 00:24:14,854 --> 00:24:17,790 making Jupiter, say, appear 30 times closer. 279 00:24:17,824 --> 00:24:24,030 Our cosmic telescope can make things appear 100 billion times closer. 280 00:24:24,063 --> 00:24:27,466 And we can aim it at almost any direction. 281 00:24:27,500 --> 00:24:32,572 Our detector array moves 360 degrees around the sun. 282 00:24:32,605 --> 00:24:36,042 There's only one part of the cosmos that's off-limits to us 283 00:24:36,075 --> 00:24:38,778 and that's the heart of our own Milky Way Galaxy, 284 00:24:38,811 --> 00:24:40,747 which is just too bright. 285 00:24:40,780 --> 00:24:42,749 Its radiance is blinding. 286 00:24:42,782 --> 00:24:44,584 But with a telescope like this one, 287 00:24:44,617 --> 00:24:47,119 so much else that has been foreclosed to us, 288 00:24:47,153 --> 00:24:50,422 would be made visible. 289 00:24:55,327 --> 00:24:59,465 A possible world, perhaps. 290 00:24:59,498 --> 00:25:04,336 The mixture of gases in its atmosphere can tell us if life is there. 291 00:25:06,038 --> 00:25:08,841 Molecules have specific color signatures. 292 00:25:08,875 --> 00:25:12,011 If we look at this atmosphere through a spectroscope, 293 00:25:12,044 --> 00:25:16,015 an instrument that breaks down light into its constituent colors, 294 00:25:16,048 --> 00:25:20,152 we'll be able to identify the molecules that make up the atmosphere. 295 00:25:20,987 --> 00:25:25,391 The presence of oxygen and methane are tell-tale signs of life. 296 00:25:28,828 --> 00:25:32,531 This world is alive and our cosmic telescope could 297 00:25:32,565 --> 00:25:36,102 give us a complete picture of its entire surface. 298 00:25:39,238 --> 00:25:41,440 It's not just an optical telescope, 299 00:25:41,473 --> 00:25:43,876 one that can only see visible light. 300 00:25:43,910 --> 00:25:46,545 It's also a radio telescope. 301 00:25:46,579 --> 00:25:50,549 Just as it can magnify light from distant worlds 100 billion times, 302 00:25:50,583 --> 00:25:53,986 it can do the same for radio waves. 303 00:25:54,020 --> 00:25:56,756 There is something astronomers call a "water hole." 304 00:25:56,789 --> 00:25:59,125 It's named after that place where the lions and 305 00:25:59,158 --> 00:26:01,994 the water buffalo gather to drink and bathe. 306 00:26:02,028 --> 00:26:04,396 (radio static). 307 00:26:04,430 --> 00:26:06,532 It's a region of the radio spectrum, 308 00:26:06,565 --> 00:26:09,602 where interference is at a minimum and we can eavesdrop 309 00:26:09,636 --> 00:26:11,904 on even the faintest transmissions between 310 00:26:11,938 --> 00:26:14,573 far-flung civilizations. 311 00:26:14,607 --> 00:26:17,710 We would need to use all of our computing power to decrypt 312 00:26:17,744 --> 00:26:20,613 the signals hidden in the noise. 313 00:26:23,015 --> 00:26:27,486 (radio static). 314 00:26:27,519 --> 00:26:29,421 MAN (over radio): 1-4-1-5-9-2-6. 315 00:26:29,455 --> 00:26:35,494 (radio chatter). 316 00:26:37,563 --> 00:26:43,836 TYSON: And this vast telescope is also a means for seeing back in time. 317 00:26:46,105 --> 00:26:50,109 You can't look across space without seeing an object in the past. 318 00:26:50,142 --> 00:26:53,946 That's because the speed of light is finite. 319 00:26:53,980 --> 00:26:57,116 In the morning, look up at the sun and see it as 320 00:26:57,149 --> 00:27:01,120 it was eight minutes and 20 seconds ago. 321 00:27:01,153 --> 00:27:04,590 You'll never see it any other way. 322 00:27:04,623 --> 00:27:07,326 That's because it takes that long for light from the 323 00:27:07,359 --> 00:27:11,764 sun to travel the 93 million miles to Earth. 324 00:27:11,798 --> 00:27:14,701 And when we look at any world through this telescope, 325 00:27:14,734 --> 00:27:18,304 we're seeing it in the past. 326 00:27:21,340 --> 00:27:25,477 Now, imagine the cosmic telescope of another civilization. 327 00:27:25,511 --> 00:27:29,581 Say, one that's 5,000 lightyears from Earth. 328 00:27:29,615 --> 00:27:32,618 The astronomers of that world could witness the building 329 00:27:32,651 --> 00:27:34,787 of the pyramids in Egypt. 330 00:27:34,821 --> 00:27:39,625 Or follow the Polynesian voyages as they bravely made their way across the Pacific. 331 00:27:40,492 --> 00:27:44,096 But perhaps the most important use of the cosmic telescope, 332 00:27:44,130 --> 00:27:47,433 would be our search for new Earths. 333 00:27:47,466 --> 00:27:50,870 What I can't understand is, why we haven't built one. 334 00:27:50,903 --> 00:27:53,840 We already know how to do it. 335 00:27:53,873 --> 00:27:56,943 We have the technology right now. 336 00:28:01,714 --> 00:28:05,017 When would you like the future to begin? 337 00:28:22,668 --> 00:28:24,403 TYSON: Okay. 338 00:28:24,436 --> 00:28:27,740 We've got the biggest dreams of putting our eyes on other worlds. 339 00:28:27,774 --> 00:28:31,143 Traveling to them, making them our home. 340 00:28:31,177 --> 00:28:33,612 But, how do we get there? 341 00:28:33,645 --> 00:28:36,015 The stars are so far apart. 342 00:28:36,048 --> 00:28:39,351 We would need sailing ships that could sustain human crews 343 00:28:39,385 --> 00:28:42,454 over the longest haul of all time. 344 00:28:42,488 --> 00:28:45,992 The nearest star is four lightyears away. 345 00:28:46,025 --> 00:28:50,729 That's 24 trillion miles to Proxima Centuri. 346 00:28:56,335 --> 00:28:59,605 Just to give you some idea of how far away that point 347 00:28:59,638 --> 00:29:01,740 of light really is? 348 00:29:01,774 --> 00:29:04,110 If NASA's Voyager One spacecraft, 349 00:29:04,143 --> 00:29:06,045 which moves at a pretty good clip, 350 00:29:06,078 --> 00:29:08,014 38,000 miles an hour, 351 00:29:08,047 --> 00:29:10,482 was headed for Proxima Centuri? 352 00:29:10,516 --> 00:29:14,086 It would take 70,000 years to get there. 353 00:29:14,120 --> 00:29:16,856 And that's only the nearest star out of 354 00:29:16,889 --> 00:29:21,227 the hundreds of billions in our galaxy alone. 355 00:29:30,937 --> 00:29:34,606 So, if we want to endure as a species beyond the projected 356 00:29:34,640 --> 00:29:36,775 shelf life of our own planet, 357 00:29:36,809 --> 00:29:39,946 we'd better act like the Polynesians. 358 00:29:39,979 --> 00:29:43,215 We need to take what we know of nature and build sailing 359 00:29:43,249 --> 00:29:49,321 ships that can ride the light as they once rode the wind. 360 00:29:54,260 --> 00:29:57,596 These sails are enormous, miles high, 361 00:29:57,629 --> 00:29:59,531 but they're very thin. 362 00:29:59,565 --> 00:30:02,869 1,000 times thinner than a garbage bag. 363 00:30:10,109 --> 00:30:16,949 * 364 00:30:18,650 --> 00:30:22,488 When a photon of light strikes those magnificent sails 365 00:30:22,521 --> 00:30:24,656 it gives them a little push. 366 00:30:28,294 --> 00:30:35,134 * 367 00:30:35,734 --> 00:30:38,304 This means then, in the vacuum of space, 368 00:30:38,337 --> 00:30:43,075 even the tiniest push from a photon will propel them ever faster, 369 00:30:43,109 --> 00:30:47,679 until they're moving at a significant fraction of the speed of light. 370 00:30:54,887 --> 00:30:57,689 When you get too far from your star and the light dwindles, 371 00:30:57,723 --> 00:31:01,693 lasers can do the trick. 372 00:31:07,233 --> 00:31:14,006 * 373 00:31:19,611 --> 00:31:23,349 If we were to light-sail our way to Proxima Centuri, 374 00:31:23,382 --> 00:31:25,651 it wouldn't take 70,000 years. 375 00:31:25,684 --> 00:31:29,521 But only 20 years. 376 00:31:35,127 --> 00:31:39,031 Proxima B lies in the habitable zone of its star. 377 00:31:39,065 --> 00:31:42,834 But we don't yet know if it could support life. 378 00:31:42,868 --> 00:31:45,337 Does it have the kind of protective magnetic field that 379 00:31:45,371 --> 00:31:50,042 has sheltered the evolution of life on the surface of our world? 380 00:31:52,378 --> 00:31:55,114 Another consequence of Proxima B's close location to its 381 00:31:55,147 --> 00:31:59,651 star is that the planet is probably tidily locked. 382 00:32:00,752 --> 00:32:03,922 One side perpetually facing the star. 383 00:32:03,956 --> 00:32:07,526 The other? Doomed to endless night. 384 00:32:15,634 --> 00:32:22,408 * 385 00:32:23,275 --> 00:32:27,613 (rumbling). 386 00:32:27,646 --> 00:32:30,116 These little stars may be lukewarm, 387 00:32:30,149 --> 00:32:33,085 but they have a long future ahead of them. 388 00:32:33,119 --> 00:32:35,454 Trillions of years. 389 00:32:35,487 --> 00:32:38,124 Think of the continuity and growth potential of 390 00:32:38,157 --> 00:32:43,395 a civilization with a future measured in trillions of years? 391 00:32:44,730 --> 00:32:47,599 It's always magic hour on this strip of land that lies 392 00:32:47,633 --> 00:32:52,104 between day and night of this world. 393 00:32:52,138 --> 00:32:55,441 If Proxima B is habitable, its life would be confined 394 00:32:55,474 --> 00:32:57,976 to this twilight zone. 395 00:32:58,010 --> 00:33:00,779 It could be a home for the indigenous life here or 396 00:33:00,812 --> 00:33:05,451 a possible campsite for our descendants. 397 00:33:06,718 --> 00:33:11,757 The gravity on Proxima B is about 10% greater than ours on Earth. 398 00:33:12,458 --> 00:33:14,626 No real problem for us. 399 00:33:14,660 --> 00:33:18,130 Just a little like exercising with weights on. 400 00:33:20,899 --> 00:33:24,036 Remote scanning from orbit found no apparent signs of 401 00:33:24,070 --> 00:33:28,840 life making Proxima B a waystation on a much grander 402 00:33:28,874 --> 00:33:32,544 interstellar diaspora of Earthlings. 403 00:33:32,578 --> 00:33:35,914 But for those longer trips? 404 00:33:35,947 --> 00:33:39,551 We're gonna need a faster boat. 405 00:33:40,519 --> 00:33:44,623 Let's say we found a system located 100 light-years from home. 406 00:33:44,656 --> 00:33:48,060 One with several potentially habitable worlds. 407 00:33:48,094 --> 00:33:52,664 For light-sailors, that would be a 500 year long trip. 408 00:33:52,698 --> 00:33:56,668 Is it possible to build a ship that could break the cosmic speed limit? 409 00:33:57,703 --> 00:34:01,807 A mathematical physicist, Miguel Alcubierre of Mexico, 410 00:34:01,840 --> 00:34:05,277 inspired by the original Star Trek television series, 411 00:34:05,311 --> 00:34:08,080 conceived the calculations for a ship that could 412 00:34:08,114 --> 00:34:11,883 theoretically travel faster than the speed of light. 413 00:34:11,917 --> 00:34:15,221 If successful, it could cut the travel time between 414 00:34:15,254 --> 00:34:20,359 our sun and this distant star system down to a single year or even less. 415 00:34:21,227 --> 00:34:24,630 But wait a minute, isn't it a cardinal rule of science 416 00:34:24,663 --> 00:34:28,100 that "thou shalt not travel faster than light?" 417 00:34:28,134 --> 00:34:29,735 It is. 418 00:34:29,768 --> 00:34:32,871 But here's the thing about the Alcubierre Drive. 419 00:34:32,904 --> 00:34:37,008 It doesn't move, the cosmos does. 420 00:34:37,042 --> 00:34:41,180 The ship itself would be enclosed in its own space-time bubble. 421 00:34:41,213 --> 00:34:44,116 Where it needn't violate any laws of physics. 422 00:34:44,150 --> 00:34:47,753 Harold White of the United States ironed out some of the kinks. 423 00:34:47,786 --> 00:34:52,458 Such as prohibitively enormous energy requirements to fly it. 424 00:34:53,625 --> 00:34:58,230 But it remains far beyond our immediate grasp. 425 00:34:59,465 --> 00:35:02,568 The Alcubierre Drive Ship is a gravitational wave making 426 00:35:02,601 --> 00:35:05,637 machine, that compresses the ocean of space-time 427 00:35:05,671 --> 00:35:10,041 in front of it and expands that ocean in its wake. 428 00:35:10,075 --> 00:35:15,080 Jet skis for joyriding through the galaxy and beyond. 429 00:35:15,781 --> 00:35:17,583 Who knows? 430 00:35:17,616 --> 00:35:22,254 Maybe the entire Laniakea supercluster could one day become our pond. 431 00:35:22,288 --> 00:35:25,591 That's 100,000 galaxies. 432 00:35:25,624 --> 00:35:31,797 Laniakea, the phrase in Hawaiian for "immeasurable heaven." 433 00:35:33,265 --> 00:35:35,601 An advanced version of our Alcubierre Drive 434 00:35:35,634 --> 00:35:40,839 could do 600 trillion miles in the blink of an eye. 435 00:35:44,276 --> 00:35:49,315 Before you know it, you're in the planetary system of a distant star. 436 00:35:49,348 --> 00:35:52,418 Let's call it, the "Hoku" system. 437 00:35:52,451 --> 00:35:57,689 A red dwarf star surrounded by a retinue of rocky and ice giant planets. 438 00:35:57,723 --> 00:36:01,760 Somewhere among them is a world that we have come to call home. 439 00:36:01,793 --> 00:36:05,731 Our cosmic telescope sifted through all the stars within 440 00:36:05,764 --> 00:36:10,702 a radius of 100 light years and pointed the way to this one. 441 00:36:10,736 --> 00:36:14,139 All seven of these planets, huddle closer to their star 442 00:36:14,172 --> 00:36:17,876 than Mercury does to our sun. 443 00:36:20,412 --> 00:36:24,983 Haumia is just on the outskirts of Hoku's habitable zone. 444 00:36:25,016 --> 00:36:28,153 Those warm green colors seem inviting, 445 00:36:28,186 --> 00:36:30,989 but we're not seeing the tops of forests. 446 00:36:31,022 --> 00:36:34,326 That green comes from methane and ammonia. 447 00:36:34,360 --> 00:36:37,329 Even at a distance of only 27 million miles, 448 00:36:37,363 --> 00:36:41,467 the star Hoku is too weak to keep this planet warm. 449 00:36:44,403 --> 00:36:49,040 We are now in the sweet spot of Hoku's habitable zone. 450 00:36:50,676 --> 00:36:53,779 And this is the planet Tangaroa, 451 00:36:53,812 --> 00:36:58,083 where the latest chapter of the saga of our species is playing out. 452 00:37:04,423 --> 00:37:09,561 It took a few hundred years for humans to terraform this lifeless world. 453 00:37:09,595 --> 00:37:14,400 But now, even the air tastes as sweet as home. 454 00:37:20,906 --> 00:37:24,343 But this was only Indonesia. 455 00:37:24,376 --> 00:37:27,212 One of the earlier stops on our nomadic odyssey throughout 456 00:37:27,245 --> 00:37:29,047 the Milky Way. 457 00:37:29,080 --> 00:37:33,018 There were still so many islands that lay ahead. 458 00:37:39,525 --> 00:37:42,894 And in this dream future of ours, 459 00:37:42,928 --> 00:37:45,697 with our faster than light craft? 460 00:37:45,731 --> 00:37:49,034 There would come a time when we could place our cosmic telescope 461 00:37:49,067 --> 00:37:53,539 far enough away from our home planet to see first-hand, 462 00:37:53,572 --> 00:37:59,778 those of our nameless ancestors who first set sail on unknown seas. 463 00:38:15,126 --> 00:38:19,998 (radio static). 464 00:38:33,612 --> 00:38:38,484 TYSON: Carl Sagan made this drawing when he was a child. 465 00:38:38,517 --> 00:38:42,788 Imagining the unfolding of the next Golden Age of Exploration. 466 00:38:52,063 --> 00:38:56,101 As a scientist, he played a central role in it. 467 00:38:56,134 --> 00:39:00,005 And now, he speaks to us out of the past. 468 00:39:00,038 --> 00:39:03,775 About our dreams of the future. 469 00:39:06,778 --> 00:39:09,815 SAGAN: Are we to venture out into space? 470 00:39:09,848 --> 00:39:12,851 Move worlds, re-engineer planets, 471 00:39:12,884 --> 00:39:16,187 spread to neighboring star systems? 472 00:39:16,221 --> 00:39:19,791 We, who cannot even put our own planetary home in order, 473 00:39:19,825 --> 00:39:23,161 riven with rivalries and hatreds. 474 00:39:23,194 --> 00:39:26,164 Despoiling our environment, murdering one another through 475 00:39:26,197 --> 00:39:29,100 irritation and inattention. 476 00:39:29,134 --> 00:39:33,138 As well as on deadly purpose and moreover, a species that, 477 00:39:33,171 --> 00:39:36,542 until only recently, was convinced that the whole 478 00:39:36,575 --> 00:39:38,710 universe was made for its sole benefit. 479 00:39:42,047 --> 00:39:46,151 I do not imagine that it is precisely 'we.' 480 00:39:46,184 --> 00:39:51,222 With our present customs and social conventions who will be out there. 481 00:39:52,558 --> 00:39:55,827 If we continue to accumulate only power and not wisdom, 482 00:39:55,861 --> 00:39:57,996 we will surely destroy ourselves. 483 00:40:00,231 --> 00:40:05,203 Our very existence in that distant time requires 484 00:40:05,236 --> 00:40:10,041 that we will have changed our institutions and ourselves. 485 00:40:12,343 --> 00:40:16,915 How can I dare to guess about humans in the far future? 486 00:40:16,948 --> 00:40:20,886 It is, I think, only a matter of natural selection. 487 00:40:20,919 --> 00:40:26,091 If we become even slightly more violent, short-sighted, 488 00:40:26,124 --> 00:40:29,461 ignorant and selfish than we are now. 489 00:40:29,495 --> 00:40:33,431 Almost certainly, we will have no future. 490 00:40:35,601 --> 00:40:39,771 If you're young, it's just possible that we will 491 00:40:39,805 --> 00:40:42,941 be taking our first steps on near-Earth asteroids and 492 00:40:42,974 --> 00:40:46,545 Mars during your lifetime. 493 00:40:46,578 --> 00:40:50,415 By the time we're ready to settle even the nearest other 494 00:40:50,448 --> 00:40:54,753 planetary systems, we will have changed. 495 00:40:54,786 --> 00:40:58,790 The simple passage of so many generations will have changed us. 496 00:40:58,824 --> 00:41:02,828 The different circumstances we will be living under will have changed us. 497 00:41:04,195 --> 00:41:08,967 We're an adaptable species. 498 00:41:14,506 --> 00:41:17,909 It will not be we who reach Alpha Centauri 499 00:41:17,943 --> 00:41:20,078 and the other nearby stars. 500 00:41:20,111 --> 00:41:23,014 It will be a species very like us, 501 00:41:23,048 --> 00:41:28,019 but with more of our strengths and fewer of our weaknesses. 502 00:41:32,423 --> 00:41:35,260 A species returned to circumstances, 503 00:41:35,293 --> 00:41:39,264 more like those for which it was originally evolved. 504 00:41:39,931 --> 00:41:45,103 More confident, far-seeing, capable and prudent. 505 00:41:46,204 --> 00:41:49,240 The sorts of beings we would want to represent us 506 00:41:49,274 --> 00:41:52,711 in a universe that, for all we know, 507 00:41:52,744 --> 00:41:56,014 is filled with species much older, 508 00:41:56,047 --> 00:41:59,551 much more powerful and very different. 509 00:42:06,725 --> 00:42:12,063 The vast distances that separate the stars are providential. 510 00:42:13,498 --> 00:42:18,536 Beings and worlds are quarantined one from another. 511 00:42:20,138 --> 00:42:23,809 The quarantine is lifted, only for those with sufficient 512 00:42:23,842 --> 00:42:30,348 self-knowledge and judgement to have safely traveled from star to star. 513 00:42:32,017 --> 00:42:38,356 * 514 00:42:41,893 --> 00:42:46,197 Our remote descendants safely arrayed on many worlds through 515 00:42:46,231 --> 00:42:51,236 the solar system and beyond will be unified by 516 00:42:51,269 --> 00:42:55,907 their common heritage, by their regard for their 517 00:42:55,941 --> 00:43:02,280 home planet and by the knowledge that whatever other life may be, 518 00:43:02,313 --> 00:43:06,384 the only humans in all the universe come from Earth. 519 00:43:06,885 --> 00:43:13,625 ("Thank you, mother" in native languages). 520 00:43:13,892 --> 00:43:16,695 MAN: Thank you, mother. 521 00:43:52,964 --> 00:43:54,966 Captioned by Cotter Captioning Services.