1 00:00:06,758 --> 00:00:07,967 [narrator] Fifty years ago, 2 00:00:08,051 --> 00:00:11,054 astronomers picked up this radio signal coming from deep space. 3 00:00:11,679 --> 00:00:13,723 The signal repeated so regularly, 4 00:00:13,806 --> 00:00:15,933 it kept time better than an atomic clock. 5 00:00:16,601 --> 00:00:20,897 [imitates signal] What could that be? That couldn't be natural. 6 00:00:20,980 --> 00:00:23,024 [narrator] They thought it might be an alien transmission, 7 00:00:23,107 --> 00:00:27,612 so they nicknamed the signal LGM-1, for Little Green Men. 8 00:00:27,695 --> 00:00:30,114 It turned out to be a pulsar, 9 00:00:30,239 --> 00:00:35,119 radio waves from a neutron star collapsing 5.5 million years ago. 10 00:00:36,037 --> 00:00:39,582 A lot of us put aliens in the same category as ghosts 11 00:00:39,665 --> 00:00:42,919 or the Loch Ness Monster, a subject for science fiction. 12 00:00:43,002 --> 00:00:47,048 Or left to the cranks, kooks and conspiracy theorists. 13 00:00:47,131 --> 00:00:49,550 [man] Immediately, I was just lifted from the ground, 14 00:00:49,634 --> 00:00:52,178 to about the height that they were off the ground. 15 00:00:52,261 --> 00:00:56,516 That's when I first saw this thing coming straight down, just like an elevator. 16 00:00:56,599 --> 00:01:00,144 This is a center for the distribution of information 17 00:01:00,228 --> 00:01:02,939 coming through me telepathically from the space people. 18 00:01:03,022 --> 00:01:04,607 [narrator] But time and again, 19 00:01:04,690 --> 00:01:07,693 serious scientists have thought they've found evidence 20 00:01:07,777 --> 00:01:10,113 of extraterrestrial life. 21 00:01:10,196 --> 00:01:14,784 [man] Are these really canals on Mars? Are the polar caps frozen water? 22 00:01:15,785 --> 00:01:18,246 [narrator] As recently as 2016, 23 00:01:18,329 --> 00:01:22,041 astronomers proposed that never-before-seen dimming patterns 24 00:01:22,125 --> 00:01:26,087 from a star could be evidence of gigantic structures built 25 00:01:26,170 --> 00:01:29,298 by an advanced civilization to harness the star's energy. 26 00:01:29,924 --> 00:01:32,301 It turned out to be dust. 27 00:01:32,385 --> 00:01:36,430 Scientists feel confident that there is biology beyond Earth. 28 00:01:36,514 --> 00:01:38,266 Not because we've found it, we haven't found it. 29 00:01:38,349 --> 00:01:41,602 The reason that we think that they're out there is simply, if not, 30 00:01:41,686 --> 00:01:43,938 then Earth is some sort of miracle. 31 00:01:44,605 --> 00:01:46,649 [narrator] For most scientists who study the universe, 32 00:01:46,732 --> 00:01:49,026 searching for aliens isn't crazy. 33 00:01:49,235 --> 00:01:51,654 What's crazy is that we haven't found them. 34 00:01:51,737 --> 00:01:55,867 In a universe so vast, where is everybody? 35 00:01:56,242 --> 00:01:59,662 [Stephen Hawking] It is important to us to know if we are alone in the dark. 36 00:01:59,745 --> 00:02:02,999 Unidentified objects that sound warning klaxons around the world. 37 00:02:03,082 --> 00:02:06,210 [man] Oh, my gosh, look at that thing. It's resting! 38 00:02:06,711 --> 00:02:10,006 [Ronald Reagan] How quickly our differences would vanish 39 00:02:10,089 --> 00:02:13,718 if we were facing an alien threat from outside this world. 40 00:02:13,801 --> 00:02:16,220 Out there is a million other civilizations. 41 00:02:16,304 --> 00:02:17,889 They all look fabulously ugly. 42 00:02:17,972 --> 00:02:20,266 And they're all a lot smarter than us. 43 00:02:20,349 --> 00:02:22,351 [theme music playing] 44 00:02:28,232 --> 00:02:31,235 Trash cans been vanishing from city sidewalks in alarming numbers. 45 00:02:31,319 --> 00:02:34,906 [narrator] Stolen trash cans are a time-honored public nuisance. 46 00:02:34,989 --> 00:02:37,283 You may have seen local news reports about it. 47 00:02:38,284 --> 00:02:42,747 The New Yorker magazine even published a cartoon about it back in 1950, 48 00:02:42,830 --> 00:02:45,541 blaming mischievous aliens. 49 00:02:45,625 --> 00:02:49,629 That silly joke inspired one of the most profound insights 50 00:02:49,712 --> 00:02:51,589 in modern scientific history. 51 00:02:52,381 --> 00:02:55,092 Because the physicist Enrico Fermi saw that cartoon, 52 00:02:55,176 --> 00:02:58,429 and the story goes, blurted out, "Where is everybody?" 53 00:02:58,721 --> 00:03:01,474 The fact that we haven't found any evidence of aliens 54 00:03:01,557 --> 00:03:03,976 became known as the Fermi Paradox. 55 00:03:04,477 --> 00:03:08,481 There are about ten to the power of 22 total stars. 56 00:03:08,564 --> 00:03:13,277 That's about 10,000 stars for every grain of sand on Earth. 57 00:03:13,361 --> 00:03:16,656 A conservative scientific estimate says 5% 58 00:03:16,739 --> 00:03:19,158 of those stars are similar to our sun, 59 00:03:19,242 --> 00:03:23,955 which means 500 billion billion suns in the universe. 60 00:03:24,789 --> 00:03:28,584 Many scientists are more confident than ever that aliens exist 61 00:03:28,668 --> 00:03:32,838 because of some game changing discoveries in the last few decades. 62 00:03:34,632 --> 00:03:37,885 Nobody could say for sure if there were any planets 63 00:03:37,969 --> 00:03:40,638 outside of our solar system, until the 1990s. 64 00:03:40,721 --> 00:03:45,601 Now, scientists think one in five sun-like stars is a planet... 65 00:03:45,685 --> 00:03:46,894 similar to our own. 66 00:03:47,561 --> 00:03:50,022 When I get asked what are the chances there's life out there, 67 00:03:50,106 --> 00:03:51,983 I always answer 100%. 68 00:03:52,775 --> 00:03:54,860 Just because there's so many stars and planets... 69 00:03:54,944 --> 00:03:57,530 we think pretty much every star has planets. 70 00:03:57,613 --> 00:03:59,949 [narrator] We've also discovered life on Earth 71 00:04:00,116 --> 00:04:03,077 in environments where nobody expected to find it. 72 00:04:03,786 --> 00:04:06,247 We see life all the way deep in the sub-surface of the planet, 73 00:04:06,330 --> 00:04:08,165 miles down, in like, gold mines. 74 00:04:08,249 --> 00:04:10,209 We see life near volcanic calderas. 75 00:04:10,293 --> 00:04:12,044 We see life on nuclear reactors. 76 00:04:12,128 --> 00:04:14,422 We see life in the most extremes. 77 00:04:14,964 --> 00:04:18,301 That actually gives us lot of hope for the search for life elsewhere, 78 00:04:18,384 --> 00:04:20,511 'cause we can't necessarily expect that all planets 79 00:04:20,594 --> 00:04:22,847 will have just the same conditions as Earth. 80 00:04:22,930 --> 00:04:27,059 [narrator] Estimates of how many Earth-like planets will develop life vary. 81 00:04:27,476 --> 00:04:30,396 So, let's say even with this new scientific confidence, 82 00:04:30,479 --> 00:04:32,440 it's just one out of every thousand. 83 00:04:32,773 --> 00:04:35,526 That means every tenth grain of sand on Earth 84 00:04:35,693 --> 00:04:38,029 represents a planet with life on it. 85 00:04:38,529 --> 00:04:43,242 And if just one out of every thousand of those planets develop intelligent life, 86 00:04:43,326 --> 00:04:47,621 that's a quadrillion intelligent alien civilizations in the universe. 87 00:04:47,913 --> 00:04:50,207 10,000 just in our galaxy. 88 00:04:50,958 --> 00:04:55,379 Extraterrestrial life also has time on its side. 89 00:04:55,838 --> 00:04:58,466 Earth is only about a third as old as the universe. 90 00:04:58,549 --> 00:05:00,426 And so there's been plenty of time 91 00:05:00,760 --> 00:05:03,971 for life to evolve to advanced civilizations and for these civilizations to spread across the galaxy. 92 00:05:07,433 --> 00:05:11,854 [narrator] With all that time and space, the math seems pretty clear. 93 00:05:11,937 --> 00:05:16,609 We should've found aliens by now, or they should have found us. 94 00:05:18,569 --> 00:05:23,532 There's one popular explanation for why we haven't found evidence of aliens. 95 00:05:23,616 --> 00:05:24,867 We have found it. 96 00:05:24,950 --> 00:05:27,286 Governments have just covered it up. 97 00:05:27,578 --> 00:05:32,166 I believe that the flying saucers seen by veteran airline and Air Force pilots 98 00:05:32,249 --> 00:05:34,293 are objects from another planet. 99 00:05:34,460 --> 00:05:36,670 Our critics continually charge 100 00:05:36,754 --> 00:05:39,382 that the United States Air Force is withholding information 101 00:05:39,465 --> 00:05:41,759 from the general public on this subject. 102 00:05:41,842 --> 00:05:44,220 This is absolutely untrue. 103 00:05:44,303 --> 00:05:45,846 [narrator] Every so often, 104 00:05:45,930 --> 00:05:49,225 something comes out that gives this theory new life, 105 00:05:49,558 --> 00:05:54,522 like the revelation in 2017 that the US government had spent millions 106 00:05:54,605 --> 00:05:58,484 on a secret program to investigate UFO sightings. 107 00:06:00,069 --> 00:06:02,822 [narrator] But as almost any scientist will tell you, 108 00:06:02,905 --> 00:06:08,452 looking into UFOs isn't the same as searching for extraterrestrial life. 109 00:06:09,078 --> 00:06:12,873 The word UFO is "unidentified flying object." 110 00:06:13,207 --> 00:06:14,500 It's unidentified. 111 00:06:14,583 --> 00:06:18,129 So, by definition, we have to leave it open. 112 00:06:18,212 --> 00:06:22,800 It doesn't mean it's been identified as an alien spacecraft. 113 00:06:22,883 --> 00:06:25,928 [narrator] Scientists have their own favorite theories about 114 00:06:26,095 --> 00:06:28,097 why we haven't found aliens. 115 00:06:28,722 --> 00:06:31,267 It could be that they came here, 116 00:06:31,350 --> 00:06:33,436 didn't like what they found and moved on. 117 00:06:33,519 --> 00:06:37,106 Imagine for a moment, you get an infestation of ants in your house. 118 00:06:37,189 --> 00:06:38,732 It happens. 119 00:06:38,816 --> 00:06:41,318 Now let's say you wanna have a conversation with those ants. 120 00:06:41,402 --> 00:06:44,321 Say, "Excuse me, can you please leave?" How would you even do that? 121 00:06:44,405 --> 00:06:46,657 I like that theory, that we're just so dumb right now. 122 00:06:46,740 --> 00:06:49,326 We're not even at the level where if they wanted to talk to us, 123 00:06:49,410 --> 00:06:53,622 these so-called intelligent creatures out there could even communicate with us. 124 00:06:53,706 --> 00:06:56,083 It could be that they've got better things to do 125 00:06:56,167 --> 00:06:58,169 than just waft around the galaxy. 126 00:06:58,252 --> 00:06:59,253 They've seen our planet, 127 00:06:59,336 --> 00:07:01,255 they just don't wanna interfere with us 128 00:07:01,338 --> 00:07:05,759 until we get to this point of technological or societal advancement 129 00:07:05,843 --> 00:07:08,637 where we're ready to be interacted with. 130 00:07:08,721 --> 00:07:11,223 Maybe the galaxy is colonized, 131 00:07:11,307 --> 00:07:12,850 maybe it's heavily colonized, 132 00:07:12,933 --> 00:07:14,602 but just not where we are. 133 00:07:14,685 --> 00:07:17,062 In other words, the fact that we seem to be alone 134 00:07:17,146 --> 00:07:19,690 may be only that we're in a backwater. 135 00:07:20,274 --> 00:07:23,944 [narrator] But it's important to remember that when Fermi calculated the odds 136 00:07:24,028 --> 00:07:25,571 that alien life is out there, 137 00:07:25,654 --> 00:07:28,073 it was just an educated guess. 138 00:07:28,657 --> 00:07:30,367 With so many stars and planets, 139 00:07:30,451 --> 00:07:33,370 he bet at least some of them will develop life, 140 00:07:33,454 --> 00:07:35,831 which would evolve and spread out. 141 00:07:35,915 --> 00:07:40,669 The trouble with this bet is there's a lot we don't know about life. 142 00:07:41,128 --> 00:07:44,548 The great filter theory helps us think about what we don't know. 143 00:07:44,632 --> 00:07:47,927 Imagine the evolution of life as a series of hurdles. 144 00:07:48,093 --> 00:07:50,804 First, molecules start replicating themselves, 145 00:07:50,888 --> 00:07:53,933 which evolves into single-cell life, then multi-cell life 146 00:07:54,016 --> 00:07:56,644 and then animals with large brains that can use tools, 147 00:07:56,727 --> 00:08:00,356 and then smarter animals that create even better tools. That's us. 148 00:08:00,439 --> 00:08:03,692 And finally, animals that can figure out how to colonize the galaxy. 149 00:08:04,443 --> 00:08:06,570 Given the size and age of the universe, 150 00:08:06,654 --> 00:08:10,533 it seems like a lot of alien species should have beat us to that last stage, 151 00:08:10,616 --> 00:08:13,953 unless one of those stages is much harder than we think. 152 00:08:14,036 --> 00:08:15,829 [Paul Davies] The view seems to be that 153 00:08:15,913 --> 00:08:18,958 given the right conditions, life will obligingly pop up, 154 00:08:19,041 --> 00:08:21,502 but the truth is, nobody has a clue. 155 00:08:21,585 --> 00:08:25,130 We have no idea how non-life turns into life. 156 00:08:25,214 --> 00:08:30,553 We know how life structures itself, but our gaps are in the major transitions. 157 00:08:30,636 --> 00:08:34,557 [narrator] We know what the major hurdles are in the evolution of life. 158 00:08:34,640 --> 00:08:37,476 Just not how hard they are to get past. 159 00:08:38,269 --> 00:08:42,481 Another example of life would help us understand life better. 160 00:08:42,565 --> 00:08:45,609 But so far, no aliens have contacted us. 161 00:08:46,151 --> 00:08:49,446 So, it's up to us to find them. 162 00:08:49,947 --> 00:08:53,742 [man] Listen to the sound of the sun and the stars. 163 00:08:54,535 --> 00:08:58,163 [Jill Tarter] I've spent my career at the SETI Institute, S-E-T-I. 164 00:08:58,247 --> 00:09:01,125 Search for Extraterrestrial Intelligence, that's the acronym. 165 00:09:01,542 --> 00:09:05,087 But in fact, we don't know how to detect intelligence directly. 166 00:09:05,546 --> 00:09:08,132 [narrator] When scientists look for intelligent aliens, 167 00:09:08,215 --> 00:09:10,718 they look for what are called technosignatures... 168 00:09:10,801 --> 00:09:13,137 evidence of alien technology. 169 00:09:13,554 --> 00:09:16,098 We want to find extraterrestrial intelligence, 170 00:09:16,223 --> 00:09:20,060 by finding something that's engineered, something that's artificial, 171 00:09:20,185 --> 00:09:21,895 something that nature can't produce. 172 00:09:21,979 --> 00:09:23,897 If I find technology... 173 00:09:24,231 --> 00:09:26,817 I'm going to presume, at least at some time... 174 00:09:27,318 --> 00:09:31,071 the existence of an intelligent technologist. 175 00:09:31,905 --> 00:09:33,073 [narrator] From up close, 176 00:09:33,157 --> 00:09:35,826 Earth has technosignatures in the form of city lights. 177 00:09:35,909 --> 00:09:38,871 From further out, aliens might notice the satellites 178 00:09:39,038 --> 00:09:40,998 and space stations orbiting our planet. 179 00:09:41,123 --> 00:09:43,626 From even further, they might pick up radio signals 180 00:09:43,709 --> 00:09:45,377 or stumble across the Voyager probes 181 00:09:45,461 --> 00:09:47,171 that are hurtling across interstellar space. 182 00:09:48,255 --> 00:09:50,883 Sometimes the things we think are technosignatures 183 00:09:50,966 --> 00:09:54,345 turn out to be natural phenomena, like that pulsar. 184 00:09:54,428 --> 00:09:58,349 But since radio signals are still our most promising leads, 185 00:09:58,432 --> 00:10:02,186 scientists do a lot of listening to the sky. 186 00:10:02,269 --> 00:10:03,771 [Tarter] If you've seen the movie Contact, 187 00:10:03,854 --> 00:10:07,358 there's Jodie Foster on the hood of the car with the earphones on. 188 00:10:07,441 --> 00:10:09,610 It's a bit ridiculous. Because in fact, 189 00:10:10,444 --> 00:10:14,615 the computer back in the observatory control room 190 00:10:14,698 --> 00:10:17,034 is doing the signal processing. 191 00:10:17,117 --> 00:10:22,122 They're analyzing the equivalent of the Encyclopedia Britannica every second. 192 00:10:22,206 --> 00:10:26,794 [narrator] Jill Tarter would know. Jodie Foster's character was based on her. 193 00:10:27,920 --> 00:10:29,421 Holy shit! 194 00:10:29,505 --> 00:10:32,216 She gets to say, "Holy shit!," you know? 195 00:10:32,299 --> 00:10:35,052 We hope to some day have that moment. 196 00:10:35,135 --> 00:10:38,764 [narrator] But that's just one way to search for extraterrestrial life. 197 00:10:38,847 --> 00:10:41,350 There are also biosignatures. 198 00:10:41,684 --> 00:10:44,061 Biosignatures are indications 199 00:10:44,353 --> 00:10:47,940 that life existed or once did exist in any given environment. 200 00:10:48,357 --> 00:10:51,527 [narrator] If aliens came to Earth looking for life after we were long gone, 201 00:10:51,777 --> 00:10:54,613 they would find biosignatures in the form of fossils 202 00:10:54,697 --> 00:10:57,032 and chemical evidence of life processes. 203 00:10:57,116 --> 00:10:59,952 My favorite line to say with kids is that all life poops. 204 00:11:00,035 --> 00:11:03,664 So we know that all life takes in energy and releases waste products. 205 00:11:04,206 --> 00:11:06,709 [narrator] If aliens were observing us from afar, 206 00:11:06,792 --> 00:11:09,878 they would see biosignatures in the form of water 207 00:11:09,962 --> 00:11:12,381 and the gases in our atmosphere. 208 00:11:12,506 --> 00:11:14,174 Oxygen is so reactive 209 00:11:14,508 --> 00:11:18,011 that it can only be in our atmosphere if it's being continuously produced. 210 00:11:18,095 --> 00:11:21,056 Without life, Earth's atmosphere would have no oxygen, 211 00:11:21,140 --> 00:11:24,226 so we're trying to look for gases that don't belong, 212 00:11:24,309 --> 00:11:27,896 that might be attributed to life, and we call them biosignature gases. 213 00:11:28,355 --> 00:11:31,442 [narrator] Searching for biosignatures on other planets is really hard. 214 00:11:31,525 --> 00:11:34,319 We can't even see planets outside our solar system. Stars are so much brighter than planets. 215 00:11:37,281 --> 00:11:39,742 It's like trying to see a firefly in a spotlight. 216 00:11:39,908 --> 00:11:43,454 Today, we have a planet finding technique called the transit technique. 217 00:11:43,537 --> 00:11:47,332 When a planet goes in front of its star, the starlight drops by a tiny amount. 218 00:11:47,416 --> 00:11:50,294 [narrator] These drops in light give scientists clues 219 00:11:50,377 --> 00:11:52,880 about whether a planet might have life on it. 220 00:11:52,963 --> 00:11:55,090 Like the distance from its star. 221 00:11:55,424 --> 00:11:58,469 We call the "Goldilocks zone" the distance from the star, 222 00:11:58,802 --> 00:12:02,055 where the planet, as heated by the star, is not too hot, 223 00:12:02,347 --> 00:12:04,641 not too cold, but just right for life. 224 00:12:05,559 --> 00:12:08,896 [narrator] Researchers have been able to surmise some amazing things about planets 225 00:12:08,979 --> 00:12:10,522 just from these light patterns. 226 00:12:10,606 --> 00:12:14,359 Scientists think they found a super Earth with really intense gravity. 227 00:12:15,152 --> 00:12:19,239 A planetary system with seven planets all crammed into the Goldilocks zone. 228 00:12:19,865 --> 00:12:22,451 And even a planet that could have red vegetation, 229 00:12:22,534 --> 00:12:24,661 from the different wavelengths of light it receives. 230 00:12:26,371 --> 00:12:30,959 We now know of over 3,500 planets outside of our solar system. 231 00:12:31,460 --> 00:12:34,671 Most of them were discovered in just the last five years. 232 00:12:34,880 --> 00:12:37,966 And tools are only getting better. 233 00:12:38,050 --> 00:12:43,305 The next generation of space telescopes will be able to see more distant galaxies. 234 00:12:43,472 --> 00:12:48,352 A newly launched satellite will survey the entire sky for possible planets, 235 00:12:48,435 --> 00:12:50,395 rather than just small sections. 236 00:12:50,562 --> 00:12:53,482 And astronomers are developing new technologies 237 00:12:53,565 --> 00:12:56,693 that would let them see distant planets directly. 238 00:12:57,319 --> 00:13:00,948 The line between what is considered completely crazy 239 00:13:01,281 --> 00:13:04,368 and what is mainstream is constantly shifting. 240 00:13:04,451 --> 00:13:08,664 [narrator] For all the exciting new ways to search for life in deep space, 241 00:13:08,831 --> 00:13:12,292 scientists are also searching a lot closer to home. 242 00:13:13,293 --> 00:13:15,128 -[man] We have landed. -[man 2] Roger. 243 00:13:15,212 --> 00:13:18,841 [narrator] In the 1970s, we sent two landers to Mars 244 00:13:18,924 --> 00:13:20,884 to test the soil for evidence of life. 245 00:13:21,426 --> 00:13:24,596 The first and only time we've ever tried. 246 00:13:24,680 --> 00:13:27,391 One of the experiments came back negative. 247 00:13:27,474 --> 00:13:31,395 But another came back positive for evidence of a process 248 00:13:31,478 --> 00:13:34,481 that we only associate with living things. 249 00:13:34,565 --> 00:13:36,525 When some of the experiments came back positive, 250 00:13:36,608 --> 00:13:39,027 and the others came back negative, it was controversial, 251 00:13:39,111 --> 00:13:41,071 because it was ambiguous. 252 00:13:41,321 --> 00:13:43,824 So it was hard to say, did we actually really find life? 253 00:13:44,324 --> 00:13:47,953 [narrator] The contradiction could mean an unknown chemical reaction occurred 254 00:13:48,036 --> 00:13:51,748 that only looked like a living thing consuming energy. 255 00:13:52,499 --> 00:13:56,670 But since the '70s, we've learned that life in extreme environments 256 00:13:56,753 --> 00:14:01,008 uses energy differently and leaves different markers on its environment. 257 00:14:01,091 --> 00:14:02,801 The experiments that were designed 258 00:14:02,885 --> 00:14:05,053 were designed based on life as we knew it back then, 259 00:14:05,137 --> 00:14:08,056 which was a very limited view of life just here on Earth. 260 00:14:08,140 --> 00:14:11,894 We need to go back to Mars and do the experiment again. 261 00:14:12,936 --> 00:14:16,064 [narrator] The Mars 2020 mission is our next shot. 262 00:14:16,648 --> 00:14:21,361 Unlike the Viking experiments, it won't test for currently living things, 263 00:14:21,445 --> 00:14:26,491 but it will look for signs that life once did exist in certain Martian environments. 264 00:14:27,242 --> 00:14:30,120 A mission is also in the works to look for biosignatures 265 00:14:30,329 --> 00:14:33,040 in the frozen oceans of Jupiter's moon Europa. 266 00:14:33,665 --> 00:14:35,792 In the search for intelligent life, 267 00:14:35,876 --> 00:14:40,505 scientists are also trying to expand their thinking and their search. 268 00:14:40,589 --> 00:14:44,676 Now, the only example we have of intelligent life is indeed us. 269 00:14:44,760 --> 00:14:46,386 You know... [laughs] 270 00:14:46,470 --> 00:14:50,015 in Star Trek, I guess it was the doctor on board, Bones, 271 00:14:50,223 --> 00:14:53,518 who'd occasionally say, "It's life, Jim, but not as we know it." 272 00:14:53,852 --> 00:14:55,771 [narrator] Actually, this is a common misquote. 273 00:14:55,854 --> 00:14:59,191 The line is a lyric in the song "Star Trekkin" by The Firm 274 00:14:59,274 --> 00:15:01,026 and was never said in the show. 275 00:15:01,151 --> 00:15:03,737 It's life, Jim, but not as we know it. [narrator] Spock, however, said something similar 276 00:15:06,490 --> 00:15:09,242 in Season One, episode 29. 277 00:15:09,326 --> 00:15:11,495 It's not life as we know or understand it. 278 00:15:12,037 --> 00:15:14,331 It is obviously alive. It exists. 279 00:15:14,414 --> 00:15:18,126 [narrator] Advances in our own technology give us new ideas 280 00:15:18,210 --> 00:15:21,171 about what intelligent aliens might be like. 281 00:15:21,505 --> 00:15:24,049 One thing that we're doing in this century 282 00:15:24,132 --> 00:15:26,426 and certainly in the first half of this century, it seems, 283 00:15:26,510 --> 00:15:29,096 is to develop artificial intelligence that does more 284 00:15:29,179 --> 00:15:31,390 than just play a good game of chess. 285 00:15:31,473 --> 00:15:34,351 Humans are the best known reference for intelligence. 286 00:15:34,434 --> 00:15:36,853 What a great standard to try to live up to. 287 00:15:36,937 --> 00:15:40,107 We think of the aliens as being like a soft and squishy biology, 288 00:15:40,190 --> 00:15:42,859 whereas in fact the majority of the intelligence in the universe 289 00:15:42,943 --> 00:15:45,112 could very well be synthetic intelligence. 290 00:15:45,487 --> 00:15:51,201 One good thing in terms of helping us to think about what we don't know 291 00:15:52,285 --> 00:15:53,453 is to read science fiction. 292 00:15:53,537 --> 00:15:56,123 Actually, Arrival was one of my favorite movies. 293 00:15:56,206 --> 00:15:59,751 Just because of the concept that the aliens could be so different 294 00:15:59,835 --> 00:16:01,169 from intelligent humanoids. 295 00:16:01,253 --> 00:16:03,505 I really think that's how it's gonna end up being. 296 00:16:05,298 --> 00:16:08,176 [narrator] Science fiction has shaped our space programs 297 00:16:08,260 --> 00:16:09,553 from the very beginning. 298 00:16:09,636 --> 00:16:13,056 [Kennda Lynch] The Martian Chronicles, War of the Worlds, many senior scientists 299 00:16:13,140 --> 00:16:16,059 were inspired by those early, early novels, 300 00:16:16,143 --> 00:16:19,646 and they've actually created the science reality of Mars exploration 301 00:16:19,730 --> 00:16:20,897 that we have today. 302 00:16:22,566 --> 00:16:24,401 [Sara Seager] It's a multi-generational search. 303 00:16:25,569 --> 00:16:26,611 We're just starting now. 304 00:16:26,695 --> 00:16:30,323 We're just kind of planting the seeds for a really long endeavor. 305 00:16:30,532 --> 00:16:32,576 [man] Velocity build up in feet per second. 306 00:16:32,659 --> 00:16:33,827 [man 2] Okay. 307 00:16:33,910 --> 00:16:37,122 [Tarter] Consider the volume of all the Earth's oceans. 308 00:16:38,331 --> 00:16:42,544 All right, and let's say, that's the volume of search space, 309 00:16:42,627 --> 00:16:45,380 where we might find a signal. 310 00:16:45,672 --> 00:16:48,717 Well, in 50 years, how much of that ocean have we searched? 311 00:16:50,177 --> 00:16:54,014 It's a pretty disappointing one glass of water. 312 00:16:55,182 --> 00:16:57,934 [narrator] Whether we find extraterrestrial life 313 00:16:58,018 --> 00:16:59,686 or learn that we are alone, 314 00:16:59,770 --> 00:17:02,898 it will tell us a lot about our civilization 315 00:17:02,981 --> 00:17:05,150 and what our future might be. 316 00:17:06,860 --> 00:17:09,237 Think back to that great filter theory. 317 00:17:09,654 --> 00:17:12,365 It could be even life rarely gets started 318 00:17:12,449 --> 00:17:16,078 or that the universe is teeming with life, but none of it... 319 00:17:16,578 --> 00:17:17,829 as smart as us. 320 00:17:18,121 --> 00:17:21,875 That is good news for the future of our civilization. 321 00:17:22,667 --> 00:17:25,337 It means that we are maybe the only planet in the galaxy 322 00:17:25,420 --> 00:17:27,297 that got as far as intelligent life, 323 00:17:27,380 --> 00:17:29,591 and there's no reason we can't be set fair 324 00:17:29,674 --> 00:17:32,636 for thousands or millions of years in the future. 325 00:17:33,261 --> 00:17:36,598 [narrator] Or maybe the hardest stage is ahead of us. 326 00:17:36,681 --> 00:17:40,102 And some unknown challenge awaits humanity. 327 00:17:40,519 --> 00:17:43,313 If life on Earth is typical and we are typical, 328 00:17:43,814 --> 00:17:47,275 but the typical thing is you don't survive very long then, 329 00:17:47,359 --> 00:17:48,777 that doesn't say much about our future. 330 00:17:49,361 --> 00:17:52,364 The importance for the search for life elsewhere in the universe 331 00:17:52,447 --> 00:17:54,991 is kind of the search in understanding ourselves. 332 00:17:55,450 --> 00:17:58,912 It's important to understanding how did we as a planet come here. 333 00:17:58,995 --> 00:18:02,666 And how rare are we or how rare are we not? 334 00:18:02,749 --> 00:18:05,627 And for humans, it's an understanding of, you know, 335 00:18:05,710 --> 00:18:07,963 what's the next big step for us.