1 00:00:02,469 --> 00:00:06,030 Freeman: Across the galaxy lie exotic worlds... 2 00:00:06,106 --> 00:00:10,338 some made entirely of water, 3 00:00:10,410 --> 00:00:13,311 others stewing with poisonous gas. 4 00:00:13,380 --> 00:00:17,441 What kinds of creatures thrive in these places? 5 00:00:19,619 --> 00:00:20,984 Would they resemble beings on Earth... 6 00:00:23,223 --> 00:00:28,627 ...or could life take on new and unexpected forms? 7 00:00:28,695 --> 00:00:31,323 What do aliens look like? 8 00:00:36,403 --> 00:00:41,033 Space, time, life itself. 9 00:00:43,276 --> 00:00:47,975 The secrets of the cosmos lie Through the Wormhole. 10 00:00:58,925 --> 00:01:01,155 They're out there. 11 00:01:01,227 --> 00:01:03,195 We can see them. 12 00:01:03,263 --> 00:01:05,595 For the first time in human history, 13 00:01:05,665 --> 00:01:08,361 we know the Universe is filled with planets 14 00:01:08,435 --> 00:01:12,098 stranger than we could ever have imagined - 15 00:01:12,172 --> 00:01:16,768 planets that might be home to extraterrestrial life. 16 00:01:16,843 --> 00:01:20,836 But what will these creatures look like? 17 00:01:20,914 --> 00:01:23,678 We're all products of our environment. 18 00:01:23,750 --> 00:01:27,618 If I was born on a planet with carbon dioxide air 19 00:01:27,687 --> 00:01:31,088 and gravity three times weaker than the Earth's, 20 00:01:31,157 --> 00:01:34,854 I might look like... this. 21 00:01:34,928 --> 00:01:38,420 On a planet with five times more gravity than Earth, 22 00:01:38,498 --> 00:01:42,798 and a star that constantly blasted it with solar storms, 23 00:01:42,869 --> 00:01:44,769 I might look like this. 24 00:01:47,073 --> 00:01:50,008 We can't know the face of an alien 25 00:01:50,076 --> 00:01:52,271 until we're staring at it. 26 00:01:52,345 --> 00:01:55,906 But like detectives on the hunt for an unknown suspect, 27 00:01:55,982 --> 00:01:58,951 biologists and planetary scientists 28 00:01:59,018 --> 00:02:02,010 are beginning to piece the puzzle together. 29 00:02:02,088 --> 00:02:05,387 Some of the clues are out there, 30 00:02:05,458 --> 00:02:08,518 but a lot of them are right here. 31 00:02:11,331 --> 00:02:13,390 To get home from school every day, 32 00:02:13,466 --> 00:02:17,960 I had to cut through the yard of a scary, old house. 33 00:02:18,037 --> 00:02:22,406 I never saw anyone come in or out of it, 34 00:02:22,475 --> 00:02:28,880 but someone or something lived there. 35 00:02:28,948 --> 00:02:33,476 I could only imagine who or what it might be. 36 00:02:39,592 --> 00:02:42,152 Harvard paleontologist Andrew Knoll 37 00:02:42,228 --> 00:02:43,559 has spent his life 38 00:02:43,630 --> 00:02:48,260 studying creatures beyond our wildest imaginations. 39 00:02:48,334 --> 00:02:50,427 Knoll: One of the things you learn 40 00:02:50,503 --> 00:02:52,971 when you go through a museum like this is 41 00:02:53,039 --> 00:02:55,098 that not only is it hard to imagine 42 00:02:55,175 --> 00:02:57,302 what life might be on another planet, 43 00:02:57,377 --> 00:02:59,811 but it's hard to imagine some of the life 44 00:02:59,879 --> 00:03:01,642 that has existed on this planet. 45 00:03:01,714 --> 00:03:04,808 Who would guess that there were things like dinosaurs 46 00:03:04,884 --> 00:03:06,613 in the absence of their bones? 47 00:03:06,686 --> 00:03:08,779 Freeman: For the past eight years, 48 00:03:08,855 --> 00:03:11,153 Andrew has served as mission biologist 49 00:03:11,224 --> 00:03:13,317 on NASA's Mars Rovers. 50 00:03:13,393 --> 00:03:15,918 It's a role he's uniquely suited for 51 00:03:15,995 --> 00:03:19,931 because of his expertise in the vast array of life on Earth, 52 00:03:19,999 --> 00:03:22,593 and his ability to read the history of a planet 53 00:03:22,669 --> 00:03:24,193 from its rocks. 54 00:03:24,270 --> 00:03:27,068 Knoll: There's a tendency for us to think about the Earth 55 00:03:27,140 --> 00:03:29,836 in terms of the things we see around us today. 56 00:03:29,909 --> 00:03:32,434 But the one thing that the geologic record tells us 57 00:03:32,512 --> 00:03:34,673 is that there have been a series of earths, 58 00:03:34,747 --> 00:03:36,840 and that the Earth that we see around us - 59 00:03:36,916 --> 00:03:38,315 all the plants and the animals 60 00:03:38,384 --> 00:03:40,352 and the composition of the atmosphere - 61 00:03:40,420 --> 00:03:42,149 are really an end-member, 62 00:03:42,222 --> 00:03:44,713 the end state of a long series of transitions 63 00:03:44,791 --> 00:03:47,055 that have happened over 4 billion years. 64 00:03:47,126 --> 00:03:49,458 For example, this rock, 65 00:03:49,529 --> 00:03:52,123 which formed about 3½ billion years ago, 66 00:03:52,198 --> 00:03:54,063 is full of iron minerals, 67 00:03:54,133 --> 00:03:57,296 which means that iron had to be able to be transported 68 00:03:57,370 --> 00:04:00,567 through seawater, and it can only do that 69 00:04:00,640 --> 00:04:03,700 in seawater that contains no oxygen. 70 00:04:03,776 --> 00:04:08,236 Freeman: The discovery of rocks like this all over Earth 71 00:04:08,314 --> 00:04:11,613 shows that for nearly the first 4 billion years 72 00:04:11,684 --> 00:04:13,652 of its existence, 73 00:04:13,720 --> 00:04:17,156 our atmosphere had almost no oxygen. 74 00:04:17,223 --> 00:04:20,681 That Earth would have been toxic to us. 75 00:04:20,760 --> 00:04:23,354 Now, there are other things that are sort of unexpected 76 00:04:23,429 --> 00:04:25,556 when we actually look at deep-earth history. 77 00:04:25,632 --> 00:04:29,466 This rock was actually deposited by glacial ice 78 00:04:29,535 --> 00:04:32,436 about 635 million years ago. 79 00:04:32,505 --> 00:04:34,029 There are rocks like this 80 00:04:34,107 --> 00:04:37,406 that formed literally all over the world at this time, 81 00:04:37,477 --> 00:04:40,241 and it shows us that there was glacial ice 82 00:04:40,313 --> 00:04:42,781 at sea level at the equator. 83 00:04:42,849 --> 00:04:44,874 In fact, much of the Earth - 84 00:04:44,951 --> 00:04:48,216 perhaps most of the Earth - was covered with ice, 85 00:04:48,288 --> 00:04:50,654 sometimes called a snowball Earth. 86 00:04:50,723 --> 00:04:52,623 Freeman: These various earths - 87 00:04:52,692 --> 00:04:56,253 hotter, colder, with more or less oxygen - 88 00:04:56,329 --> 00:04:59,457 were essentially alien worlds. 89 00:04:59,532 --> 00:05:02,558 So, for Andrew, the best place to discover 90 00:05:02,635 --> 00:05:06,833 what aliens might look like is in our own fossil records. 91 00:05:06,906 --> 00:05:08,897 Knoll: These are trilobites. 92 00:05:08,975 --> 00:05:10,465 Now, when you look at this, 93 00:05:10,543 --> 00:05:12,306 you'll see things that are familiar. 94 00:05:12,378 --> 00:05:16,144 There is a jointed, segmented body. 95 00:05:16,215 --> 00:05:18,183 There are jointed, segmented legs. 96 00:05:18,251 --> 00:05:19,582 And you might say, 97 00:05:19,652 --> 00:05:21,745 "Well, that looks like a shrimp or an insect," and that's right. 98 00:05:21,821 --> 00:05:23,311 Freeman: Biologists 99 00:05:23,389 --> 00:05:26,256 call these repeated similarities of life-forms 100 00:05:26,326 --> 00:05:29,454 over Earth's history "convergence." 101 00:05:29,529 --> 00:05:31,224 One shape that works well 102 00:05:31,297 --> 00:05:34,892 gets repeated over and over again. 103 00:05:34,967 --> 00:05:38,266 This giant sea creature looks like a whale, 104 00:05:38,338 --> 00:05:41,569 but it is actually an extinct lizard. 105 00:05:44,444 --> 00:05:48,312 Knoll: Repeatedly over the last 250 million years, 106 00:05:48,381 --> 00:05:52,681 vertebrate animals on land have re-invaded the oceans. 107 00:05:52,752 --> 00:05:54,344 And every time they've done so, 108 00:05:54,420 --> 00:05:56,980 they've given rise to these giant sea monsters. 109 00:05:57,056 --> 00:05:59,047 Kronosaurus. 110 00:05:59,125 --> 00:06:02,060 70 million years ago, there were lizards in the sea. 111 00:06:02,128 --> 00:06:03,459 They were equally large. 112 00:06:03,529 --> 00:06:06,293 In our own lifetimes, there's whales. 113 00:06:08,868 --> 00:06:11,598 Freeman: If Earth in the past 114 00:06:11,671 --> 00:06:15,004 has been as alien as planets orbiting other stars, 115 00:06:15,074 --> 00:06:17,872 then aliens you've seen in movies - 116 00:06:17,944 --> 00:06:20,242 lizards with two eyes, two arms, and two legs - 117 00:06:20,313 --> 00:06:23,339 might be pretty close to the mark. 118 00:06:28,121 --> 00:06:29,748 Labarbera: I must admit, 119 00:06:29,822 --> 00:06:33,223 I watch a lot of old monster movies from the 1950s 120 00:06:33,292 --> 00:06:35,487 specifically looking at the physics 121 00:06:35,561 --> 00:06:37,995 and saying, "No, no, no. That's not gonna work," 122 00:06:38,064 --> 00:06:40,726 or "Ooh, that's really good." 123 00:06:43,236 --> 00:06:46,501 Freeman: University of Chicago Professor Michael Labarbera 124 00:06:46,572 --> 00:06:48,506 is an expert in biomechanics. 125 00:06:48,574 --> 00:06:50,667 He's trying to predict 126 00:06:50,743 --> 00:06:54,440 how aliens will walk, fly, and swim 127 00:06:54,514 --> 00:06:57,972 by searching for the basic rule of how animals move. 128 00:06:58,050 --> 00:06:59,244 You could call it 129 00:06:59,318 --> 00:07:03,584 the lowest common denominator of locomotion. 130 00:07:06,526 --> 00:07:08,357 Labarbera: Things like horseshoe crabs 131 00:07:08,428 --> 00:07:10,862 were crawling out on the beach and laying their eggs 132 00:07:10,930 --> 00:07:13,694 when pterodactyls were flying in the sky. 133 00:07:13,766 --> 00:07:16,462 One of the features that we share with these animals 134 00:07:16,536 --> 00:07:19,130 is a lever-type skeleton. 135 00:07:19,205 --> 00:07:20,763 I have levers in my hands. 136 00:07:20,840 --> 00:07:23,001 That's what allows me to do that. 137 00:07:23,075 --> 00:07:25,339 I have levers in my elbows, in my shoulders. 138 00:07:27,613 --> 00:07:29,308 The basic idea is 139 00:07:29,382 --> 00:07:32,681 to use a lever that has a high mechanical advantage, 140 00:07:32,752 --> 00:07:34,879 that delivers a lot of the muscle force 141 00:07:34,954 --> 00:07:38,890 to the output side of the lever. 142 00:07:38,958 --> 00:07:40,653 Freeman: Successful designs 143 00:07:40,726 --> 00:07:42,956 like jointed limbs and hard skeletons 144 00:07:43,029 --> 00:07:45,896 show up again and again in the fossil record. 145 00:07:45,965 --> 00:07:47,990 We see them all around us today, 146 00:07:48,067 --> 00:07:53,528 and Michael expects to see them on other worlds, too. 147 00:07:53,606 --> 00:07:56,006 And it doesn't matter whether the skeleton 148 00:07:56,075 --> 00:07:58,635 is made out of hydroxyapatite like our bones, 149 00:07:58,711 --> 00:08:00,804 made out of chitin like this animal, 150 00:08:00,880 --> 00:08:02,006 or carbon nanotubes. 151 00:08:02,081 --> 00:08:04,072 When a principle is easy enough 152 00:08:04,150 --> 00:08:06,641 for natural selection to stumble across, 153 00:08:06,719 --> 00:08:08,710 then it will evolve over and over again. 154 00:08:08,788 --> 00:08:11,313 On this planet, it has evolved independently 155 00:08:11,390 --> 00:08:13,620 at least half a dozen different times. 156 00:08:13,693 --> 00:08:15,490 And there's every reason to believe 157 00:08:15,561 --> 00:08:16,823 they will be just as common 158 00:08:16,896 --> 00:08:19,922 in any other ecosystem on any other planet. 159 00:08:19,999 --> 00:08:22,832 Freeman: A torso with jointed limbs acting as levers. 160 00:08:22,902 --> 00:08:26,497 It's a good basic anatomy of an alien, 161 00:08:26,572 --> 00:08:32,033 but can we get closer to imagining their true form? 162 00:08:32,111 --> 00:08:34,136 In the 19th century, 163 00:08:34,213 --> 00:08:37,273 Charles Darwin kept a series of notebooks 164 00:08:37,350 --> 00:08:40,911 chronicling how the shapes of animals had evolved 165 00:08:40,987 --> 00:08:43,478 to adapt to the environments they lived in. 166 00:08:45,458 --> 00:08:48,859 What would a book of life on other planets look like? 167 00:08:48,928 --> 00:08:52,796 What mind-bending, anatomical adaptations 168 00:08:52,865 --> 00:08:57,825 might develop in alien surroundings? 169 00:08:57,904 --> 00:09:01,567 The environment shapes creatures depending on their ecology. 170 00:09:01,641 --> 00:09:03,370 Density of the atmosphere, 171 00:09:03,442 --> 00:09:07,640 whether or not you have a world-covering ocean, 172 00:09:07,713 --> 00:09:10,341 is gonna make a big difference in the history 173 00:09:10,416 --> 00:09:13,317 and, thus, in the shape of the organisms. 174 00:09:13,386 --> 00:09:15,877 Freeman: Which is why 175 00:09:15,955 --> 00:09:18,185 to know what aliens look like, 176 00:09:18,257 --> 00:09:21,886 we must learn more about the planets they live on. 177 00:09:21,961 --> 00:09:23,258 Until very recently, 178 00:09:23,329 --> 00:09:25,820 we had no proof other planets existed, 179 00:09:25,898 --> 00:09:29,356 let alone any idea what their landscapes or atmospheres 180 00:09:29,435 --> 00:09:31,198 might be like. 181 00:09:31,270 --> 00:09:34,762 But now, for the first time in human history, 182 00:09:34,840 --> 00:09:39,573 we can see worlds far outside our solar system. 183 00:09:39,645 --> 00:09:42,478 And now that we know where E.T.s could live, 184 00:09:42,548 --> 00:09:46,075 we're getting closer to revealing their hidden faces. 185 00:09:50,656 --> 00:09:53,090 If we want to know what aliens look like, 186 00:09:53,159 --> 00:09:56,526 we first have to know something about the places they live. 187 00:09:56,596 --> 00:10:00,464 Until recently, this was impossible. 188 00:10:00,533 --> 00:10:03,058 Our telescopes could only see stars, 189 00:10:03,135 --> 00:10:05,433 not the planets that orbit them. 190 00:10:05,504 --> 00:10:09,463 Today, alien hunters have a dedicated research ship 191 00:10:09,542 --> 00:10:12,739 floating 20 million miles from Earth, 192 00:10:12,812 --> 00:10:17,181 and it's discovering new worlds by the thousand. 193 00:10:21,053 --> 00:10:22,953 Man: 3... 2... 194 00:10:23,022 --> 00:10:24,046 Man # 2: Engines start. 195 00:10:24,123 --> 00:10:25,522 Man: Zero. 196 00:10:25,591 --> 00:10:28,754 And liftoff of the Delta II rocket with Kepler. 197 00:10:28,828 --> 00:10:30,955 Freeman: In 2009, 198 00:10:31,030 --> 00:10:34,431 NASA launched its latest space telescope - 199 00:10:34,500 --> 00:10:35,990 Kepler. 200 00:10:36,068 --> 00:10:38,901 It's designed not to take pictures, 201 00:10:38,971 --> 00:10:40,734 but to detect the tiniest changes 202 00:10:40,806 --> 00:10:43,172 in the brightness of distant stars. 203 00:10:43,242 --> 00:10:47,372 Its target area is a patch of our arm of the Milky Way 204 00:10:47,446 --> 00:10:51,143 stretching out 3,000 light-years away from us. 205 00:10:51,217 --> 00:10:53,685 Harvard professor Dimitar Sasselov 206 00:10:53,753 --> 00:10:56,449 is one of Kepler's lead scientists. 207 00:10:56,522 --> 00:10:59,184 The beauty of how the Kepler telescope 208 00:10:59,258 --> 00:11:01,123 discovers planets as small as the earth 209 00:11:01,193 --> 00:11:02,592 is the method, 210 00:11:02,662 --> 00:11:04,391 which we call the transit method. 211 00:11:04,463 --> 00:11:05,691 It's very easy to understand. 212 00:11:05,765 --> 00:11:09,030 So, the planet is passing on its orbit 213 00:11:09,101 --> 00:11:11,296 in front of the star. 214 00:11:11,370 --> 00:11:15,363 Its shadow causes that light to dip just a little bit, 215 00:11:15,441 --> 00:11:17,341 and that's how we know there is a planet there. 216 00:11:17,410 --> 00:11:20,811 Freeman: By the time Kepler is done with its mission, 217 00:11:20,880 --> 00:11:22,848 Dimitar expects it will have found 218 00:11:22,915 --> 00:11:26,316 around 100 planets the size of Earth. 219 00:11:26,385 --> 00:11:29,548 But the vast majority of the planets it is finding 220 00:11:29,622 --> 00:11:33,251 have almost nothing in common with our world. 221 00:11:33,325 --> 00:11:35,384 Sasselov: Kepler already has a treasure chest 222 00:11:35,461 --> 00:11:36,985 of weird planets, if you will - 223 00:11:37,063 --> 00:11:39,463 very interesting, diverse planets. 224 00:11:39,532 --> 00:11:43,798 So, we have Kepler-10, which is as hard as iron. 225 00:11:43,869 --> 00:11:45,666 Then we have two or three planets 226 00:11:45,738 --> 00:11:48,298 in the Kepler-11 system of six. 227 00:11:48,374 --> 00:11:50,342 One or two of them are water planets - 228 00:11:50,409 --> 00:11:53,139 endless ocean. 229 00:11:53,212 --> 00:11:55,146 Then we have planets 230 00:11:55,214 --> 00:11:59,674 almost the density of a beach ball or styrofoam. 231 00:11:59,752 --> 00:12:04,780 Freeman: Perhaps the most intriguing of Kepler's discoveries 232 00:12:04,857 --> 00:12:08,987 are around 300 super-sized versions of Earth - 233 00:12:09,061 --> 00:12:13,623 planets made of rock, but up to five times as heavy. 234 00:12:21,874 --> 00:12:25,241 If anyone can imagine the landscapes 235 00:12:25,311 --> 00:12:29,771 where aliens might jog, swim, or glide, 236 00:12:29,849 --> 00:12:32,511 it's Diana Valencia. 237 00:12:32,585 --> 00:12:34,143 Part-time triathlete, 238 00:12:34,220 --> 00:12:36,188 she's one of the first geologists 239 00:12:36,255 --> 00:12:40,089 to break ground on these super earths. 240 00:12:40,159 --> 00:12:42,184 Valencia: I do not have a hammer. 241 00:12:42,261 --> 00:12:43,626 I do not break up rocks. 242 00:12:43,696 --> 00:12:45,391 What I do is I do numerical models 243 00:12:45,464 --> 00:12:47,091 to understand how the Earth works 244 00:12:47,166 --> 00:12:49,157 and use that to understand 245 00:12:49,235 --> 00:12:53,194 how bigger earths and similar planets work, as well. 246 00:12:53,272 --> 00:12:54,364 Freeman: To understand 247 00:12:54,440 --> 00:12:56,908 whether the super earths could harbor life, 248 00:12:56,976 --> 00:13:00,969 Diana is zeroing in on the basic geological engine 249 00:13:01,046 --> 00:13:02,775 that powers rocky planets - 250 00:13:02,848 --> 00:13:05,510 plate tectonics. 251 00:13:05,584 --> 00:13:08,417 The movement of a planet's hard outer crust 252 00:13:08,487 --> 00:13:10,921 is driven by a hot and viscous layer 253 00:13:10,990 --> 00:13:13,322 of semi-molten rock below it 254 00:13:13,392 --> 00:13:16,884 moving much like a jar of bubbling honey. 255 00:13:16,962 --> 00:13:22,457 This experiment here shows us in broad lines what happens. 256 00:13:22,535 --> 00:13:25,402 The mantle is a very viscous fluid, 257 00:13:25,471 --> 00:13:28,565 and both fluids are very sensitive to temperature. 258 00:13:28,641 --> 00:13:33,772 So, as we turn this heat up to simulate Earth's engine, 259 00:13:33,846 --> 00:13:38,476 you will start seeing motion underneath the surface. 260 00:13:38,551 --> 00:13:40,678 Now you see the overturn. 261 00:13:40,753 --> 00:13:42,345 Now you start seeing things 262 00:13:42,421 --> 00:13:44,116 that are moving all sorts of directions. 263 00:13:44,190 --> 00:13:45,748 It's not just moving up. 264 00:13:47,326 --> 00:13:49,886 Freeman: As heat rises, 265 00:13:49,962 --> 00:13:52,931 it forms convective cells in the mantle, 266 00:13:52,998 --> 00:13:56,695 which cause the plates on the surface to shift. 267 00:13:56,769 --> 00:14:01,263 These shifts trigger volcanic eruptions and earthquakes - 268 00:14:01,340 --> 00:14:04,741 events we associate more with death than life. 269 00:14:08,080 --> 00:14:10,674 But that's just the short-term view. 270 00:14:10,749 --> 00:14:13,377 From Diana's geological perspective, 271 00:14:13,452 --> 00:14:16,979 this cycling of material from the inside of our planet 272 00:14:17,056 --> 00:14:22,153 to the atmosphere has been vital to the evolution of life. 273 00:14:22,228 --> 00:14:24,321 Valencia: Thanks to this process, 274 00:14:24,396 --> 00:14:26,091 the surface temperature of the Earth 275 00:14:26,165 --> 00:14:27,462 has not swung very much, 276 00:14:27,533 --> 00:14:29,967 and it has been around that of liquid water 277 00:14:30,035 --> 00:14:31,502 for over billions of years. 278 00:14:37,343 --> 00:14:39,971 Freeman: Super earths are bigger 279 00:14:40,045 --> 00:14:42,377 and therefore hotter on the inside. 280 00:14:42,448 --> 00:14:45,246 And when you turn up the heat, 281 00:14:45,317 --> 00:14:48,514 plate tectonics kicks into a higher gear. 282 00:14:48,587 --> 00:14:52,455 That may mean more volcanoes and more earthquakes. 283 00:14:55,294 --> 00:14:59,663 But also, a planet with a much more stable temperature. 284 00:14:59,732 --> 00:15:01,222 Valencia: On super earths, 285 00:15:01,300 --> 00:15:04,098 because convection would be much faster, 286 00:15:04,169 --> 00:15:06,729 this cycle could respond much quicker - 287 00:15:06,805 --> 00:15:09,273 perhaps an order of magnitude quicker. 288 00:15:09,341 --> 00:15:10,808 And then we can speculate 289 00:15:10,876 --> 00:15:13,902 that that has enabled the evolution of complex life. 290 00:15:13,979 --> 00:15:16,311 Freeman: Think about how a super earth 291 00:15:16,382 --> 00:15:18,646 would have dealt with the impact 292 00:15:18,717 --> 00:15:21,743 of the meteorite that wiped out the dinosaurs. 293 00:15:21,820 --> 00:15:25,756 On Earth, this event triggered an extended global winter 294 00:15:25,824 --> 00:15:29,521 that spelled the demise of those cold-blooded giants. 295 00:15:29,595 --> 00:15:32,063 But on a bigger planet, 296 00:15:32,131 --> 00:15:34,565 better able to control its temperature, 297 00:15:34,633 --> 00:15:37,761 dinosaurs might survive 298 00:15:37,836 --> 00:15:42,000 and have the chance to evolve bigger brains. 299 00:15:42,074 --> 00:15:45,373 However, there is one major downside 300 00:15:45,444 --> 00:15:48,140 to living on a giant version of Earth. 301 00:15:48,213 --> 00:15:52,946 The core of our world is a spinning ball of liquid metal 302 00:15:53,018 --> 00:15:55,748 generating a powerful magnetic field. 303 00:15:55,821 --> 00:16:00,554 That field deflects a torrent of dangerous radiation from the Sun 304 00:16:00,626 --> 00:16:05,188 and forms a protective cocoon for all life here. 305 00:16:05,264 --> 00:16:07,494 Diana's models predict 306 00:16:07,566 --> 00:16:11,662 that super earths may not have these force fields. 307 00:16:11,737 --> 00:16:13,034 Valencia: It's very possible 308 00:16:13,105 --> 00:16:15,005 that these planets do not have a molten core, 309 00:16:15,074 --> 00:16:18,373 because their interiors are under so much pressure. 310 00:16:18,444 --> 00:16:21,345 So, if you are a creature in a planet 311 00:16:21,413 --> 00:16:23,745 that doesn't have a geomagnetic field, 312 00:16:23,816 --> 00:16:26,717 you are being bombarded by high-energy particles, 313 00:16:26,785 --> 00:16:28,514 and those are interacting with your cells, 314 00:16:28,587 --> 00:16:30,077 causing mutations, probably. 315 00:16:30,155 --> 00:16:34,057 So, you have to be clever, as an organism, 316 00:16:34,126 --> 00:16:35,787 to adapt to those conditions. 317 00:16:35,861 --> 00:16:38,762 Freeman: What kind of alien could survive 318 00:16:38,831 --> 00:16:41,698 on a radiation-soaked super earth? 319 00:16:41,767 --> 00:16:44,497 It would need a protective shell, 320 00:16:44,570 --> 00:16:47,630 perhaps laced with heavy metals like lead. 321 00:16:47,706 --> 00:16:50,266 It would have powerful limbs and sharp claws 322 00:16:50,342 --> 00:16:52,333 to let it burrow under the ground 323 00:16:52,411 --> 00:16:54,072 during heavy radiation bursts. 324 00:16:54,146 --> 00:16:56,341 Most important, it would need 325 00:16:56,415 --> 00:16:59,077 effective genetic repair mechanisms 326 00:16:59,151 --> 00:17:03,554 to fix the inevitable radiation damage to its cells. 327 00:17:03,622 --> 00:17:06,284 Pure fantasy? Maybe not. 328 00:17:06,358 --> 00:17:08,826 Similar life-forms, 329 00:17:08,894 --> 00:17:12,193 albeit much smaller, called water bears, 330 00:17:12,264 --> 00:17:14,232 survive in boiling-hot, 331 00:17:14,299 --> 00:17:17,427 radiation-blasted regions on Earth. 332 00:17:17,503 --> 00:17:19,937 Inhabitants of rocky super earths 333 00:17:20,005 --> 00:17:22,735 might look surprisingly familiar. 334 00:17:22,808 --> 00:17:26,403 But imagine a world where there is no rock, 335 00:17:26,478 --> 00:17:29,572 and where creatures living in the ocean 336 00:17:29,648 --> 00:17:33,049 also fly through the sky. 337 00:17:38,323 --> 00:17:40,086 On Earth, 338 00:17:40,159 --> 00:17:44,596 evolution has produced countless variations on life - 339 00:17:44,663 --> 00:17:47,131 animals that glide through the water 340 00:17:47,199 --> 00:17:49,531 and soar through the sky. 341 00:17:49,601 --> 00:17:54,732 Beings that slither, crawl, walk, and run. 342 00:17:54,807 --> 00:17:56,775 If life on other worlds 343 00:17:56,842 --> 00:18:00,744 follows the evolutionary pattern of life here, 344 00:18:00,813 --> 00:18:05,307 what other mind-bending features might arise? 345 00:18:05,384 --> 00:18:08,842 Okay. So, you got the planet, you've got the atmosphere. 346 00:18:08,921 --> 00:18:09,910 Exaggerated. 347 00:18:09,988 --> 00:18:11,922 Yeah. 348 00:18:11,990 --> 00:18:13,685 At MIT in Cambridge, 349 00:18:13,759 --> 00:18:18,128 astrophysicist Sara Seager and biochemist William Bains 350 00:18:18,197 --> 00:18:19,630 are beginning to imagine 351 00:18:19,698 --> 00:18:22,166 what these distant worlds will be like. 352 00:18:22,234 --> 00:18:24,725 The atmosphere's gonna come from somewhere, 353 00:18:24,803 --> 00:18:27,738 so you're gonna have volcanoes producing atmosphere. 354 00:18:27,806 --> 00:18:32,038 They're trying to predict how a planet's size and composition 355 00:18:32,111 --> 00:18:33,942 will shape its biosphere. 356 00:18:34,012 --> 00:18:36,981 Before the discovery of exoplanets, 357 00:18:37,049 --> 00:18:38,346 people thought that all planetary systems 358 00:18:38,417 --> 00:18:39,441 would be like our solar system. 359 00:18:39,518 --> 00:18:40,746 And since that time, 360 00:18:40,819 --> 00:18:44,277 discoveries of exoplanets and exoplanetary systems 361 00:18:44,356 --> 00:18:47,450 have surprised us over and over and over again. 362 00:18:47,526 --> 00:18:50,324 So, what has changed? Everything has changed. 363 00:18:50,395 --> 00:18:52,090 Most science fiction assumes 364 00:18:52,164 --> 00:18:53,961 that aliens are gonna be walking around, 365 00:18:54,032 --> 00:18:55,431 they're gonna be breathing air. 366 00:18:55,501 --> 00:18:56,991 You know, they landed a starship, 367 00:18:57,069 --> 00:18:58,798 and they shared dinner with the captain. 368 00:18:58,871 --> 00:19:01,635 You look at some of the planetary environments 369 00:19:01,707 --> 00:19:02,833 out there, 370 00:19:02,908 --> 00:19:04,398 and that is not gonna happen. 371 00:19:04,476 --> 00:19:06,137 It's gonna be very different. 372 00:19:06,211 --> 00:19:09,442 Freeman: Recently, Sara and William 373 00:19:09,515 --> 00:19:13,246 have been studying GJ 1214B, 374 00:19:13,318 --> 00:19:15,445 a planet about 40 light-years away 375 00:19:15,521 --> 00:19:17,989 that's more than twice the size of Earth 376 00:19:18,056 --> 00:19:21,457 and shows signs of having an atmosphere. 377 00:19:21,527 --> 00:19:23,495 Together they are working to discover 378 00:19:23,562 --> 00:19:25,655 what it might be like 379 00:19:25,731 --> 00:19:28,666 to descend beneath the clouds of 1214B. 380 00:19:28,734 --> 00:19:30,531 Now, this planet - 381 00:19:30,602 --> 00:19:32,160 we're not totally sure what it's made of, 382 00:19:32,237 --> 00:19:35,536 but it could be a water planet with a steam atmosphere. 383 00:19:35,607 --> 00:19:38,132 And depending on the temperature of the planet, 384 00:19:38,210 --> 00:19:40,371 the clean division between liquid water 385 00:19:40,445 --> 00:19:44,814 and air with water vapor in it may not exist. 386 00:19:44,883 --> 00:19:47,784 Freeman: What sort of life could possibly emerge 387 00:19:47,853 --> 00:19:51,448 on a boiling-hot, steam world? 388 00:19:51,523 --> 00:19:53,286 Bains: So, on Earth, 389 00:19:53,358 --> 00:19:56,293 an environment like this with boiling water and steam 390 00:19:56,361 --> 00:19:58,659 is inimicable to nearly all life. 391 00:19:58,730 --> 00:20:00,755 But we're trying to imagine an alien world 392 00:20:00,832 --> 00:20:02,231 in which this is the normal environment, 393 00:20:02,301 --> 00:20:05,236 and we can now start to model a planet 394 00:20:05,304 --> 00:20:07,499 that has a huge ocean covering it 395 00:20:07,573 --> 00:20:09,734 and nevertheless is incredibly hot. 396 00:20:09,808 --> 00:20:11,799 That makes us think about, 397 00:20:11,877 --> 00:20:13,845 "Could there be life in the ocean? 398 00:20:13,912 --> 00:20:15,777 Can the chemistry work? 399 00:20:15,847 --> 00:20:17,747 And if it can, what would it look like?" 400 00:20:17,816 --> 00:20:24,187 A molecule like DNA wouldn't survive these conditions, 401 00:20:24,256 --> 00:20:26,520 but William believes 402 00:20:26,592 --> 00:20:28,924 more heat-tolerant genetic material 403 00:20:28,994 --> 00:20:31,087 would likely evolve. 404 00:20:31,163 --> 00:20:33,461 And he's beginning to imagine 405 00:20:33,532 --> 00:20:36,092 what entries might fill the pages of a book of life 406 00:20:36,168 --> 00:20:39,194 for GJ 1214B. 407 00:20:39,271 --> 00:20:42,934 The atmosphere of this planet would be mostly water. 408 00:20:43,008 --> 00:20:45,101 It would be steam. 409 00:20:45,177 --> 00:20:47,907 It would be very dense and be very hot. 410 00:20:47,980 --> 00:20:50,005 So, as you go down through it, 411 00:20:50,082 --> 00:20:53,540 you'll find drifting plants, flying plant life, 412 00:20:53,619 --> 00:20:57,077 and a whole range of organisms that eats that plant life. 413 00:20:57,155 --> 00:20:59,885 Organisms would be sort of flying fish 414 00:20:59,958 --> 00:21:02,392 or swimming birds, depending on how you look at it. 415 00:21:02,461 --> 00:21:05,521 So, they'll be able to actually fly through 416 00:21:05,597 --> 00:21:10,796 or swim through this zone almost as if it was ocean. 417 00:21:10,869 --> 00:21:15,806 Freeman: Earth's oceans gave rise to creatures of all sizes, 418 00:21:15,874 --> 00:21:19,901 but the kings of the deep are the giant filter feeders - 419 00:21:19,978 --> 00:21:22,003 whales. 420 00:21:22,080 --> 00:21:25,311 1214B could have them, too. 421 00:21:25,384 --> 00:21:27,352 So, the organism we're imagining here 422 00:21:27,419 --> 00:21:28,886 works in a very similar way. 423 00:21:28,954 --> 00:21:31,286 It might have a very different shape. 424 00:21:31,356 --> 00:21:34,052 But it moves through the ocean 425 00:21:34,126 --> 00:21:36,754 and then can move up into this interfacial zone. 426 00:21:36,828 --> 00:21:39,296 They can spend much longer in the interfacial zone 427 00:21:39,364 --> 00:21:42,959 and move much further up into it than, say, a whale breaching 428 00:21:43,035 --> 00:21:45,299 because the density is greater. 429 00:21:45,370 --> 00:21:47,770 Freeman: This aquatic world is a vision 430 00:21:47,839 --> 00:21:49,898 of what Earth might have been like 431 00:21:49,975 --> 00:21:52,569 if it were larger and wetter. 432 00:21:52,644 --> 00:21:57,581 Humans couldn't survive here, but could life find a way? 433 00:21:57,649 --> 00:22:00,846 We don't know... yet. 434 00:22:00,919 --> 00:22:03,114 There are many important things in science, 435 00:22:03,188 --> 00:22:05,679 and one of the most important ones is imagination. 436 00:22:05,757 --> 00:22:07,748 So, what is so fascinating so far - 437 00:22:07,826 --> 00:22:10,124 in exoplanets, anything is possible 438 00:22:10,195 --> 00:22:12,288 within the laws of physics and chemistry, 439 00:22:12,364 --> 00:22:15,856 and anything we imagine will exist somewhere. 440 00:22:15,934 --> 00:22:20,064 Follow the water. There, you'll find life. 441 00:22:20,138 --> 00:22:23,869 That's what the astrobiologists like to say. 442 00:22:23,942 --> 00:22:26,706 But what if there is no water? 443 00:22:26,778 --> 00:22:29,508 What about planets enveloped in toxic air 444 00:22:29,581 --> 00:22:31,845 where the building blocks of life 445 00:22:31,917 --> 00:22:36,354 are completely different from our own? 446 00:22:36,421 --> 00:22:38,981 Could they also be alive? 447 00:22:41,026 --> 00:22:44,189 Life is tenacious. 448 00:22:44,262 --> 00:22:45,786 Everywhere on Earth, 449 00:22:45,864 --> 00:22:48,560 from the coldest depths of the sea 450 00:22:48,633 --> 00:22:51,602 to the boiling fissures of volcanoes, 451 00:22:51,670 --> 00:22:54,468 living things find a way to thrive. 452 00:22:54,539 --> 00:22:57,531 But the conditions on alien planets 453 00:22:57,609 --> 00:22:59,770 could be even more extreme. 454 00:22:59,845 --> 00:23:04,111 We're discovering worlds of fire and ice, 455 00:23:04,182 --> 00:23:06,980 worlds of permanent night, 456 00:23:07,052 --> 00:23:11,455 worlds where hurricanes are constant and global. 457 00:23:11,523 --> 00:23:15,254 What kind of alien could live in these hellish places? 458 00:23:18,864 --> 00:23:23,198 Gliese 581D floats 20 light-years away from Earth 459 00:23:23,268 --> 00:23:25,862 in the constellation Libra. 460 00:23:25,937 --> 00:23:29,304 It's one of the small group of planets we have spotted 461 00:23:29,374 --> 00:23:32,343 that might harbor alien life. 462 00:23:32,411 --> 00:23:35,710 Its red star burns 463 00:23:35,781 --> 00:23:38,614 with only half the heat of our Sun, 464 00:23:38,683 --> 00:23:41,709 but because the planet spins very slowly, 465 00:23:41,787 --> 00:23:45,689 one side is much hotter than the other. 466 00:23:45,757 --> 00:23:50,217 And its rocky surface is blasted by constant wind - 467 00:23:50,295 --> 00:23:54,061 a great place to fly a kite. 468 00:23:59,304 --> 00:24:02,603 Biomechanics expert Michael Labarbera 469 00:24:02,674 --> 00:24:05,905 believes the thick atmosphere on Gliese 581D 470 00:24:05,977 --> 00:24:08,343 would shroud the surface in darkness, 471 00:24:08,413 --> 00:24:13,578 so life would have to climb up in search of light. 472 00:24:13,652 --> 00:24:18,180 He imagines kite-shaped plants that rise above the storm clouds 473 00:24:18,256 --> 00:24:21,748 to get their daily dose of solar energy. 474 00:24:21,827 --> 00:24:24,557 These kite plants have to be able to get up 475 00:24:24,629 --> 00:24:27,097 into the higher regions of the atmosphere 476 00:24:27,165 --> 00:24:28,826 in order to get enough light, 477 00:24:28,900 --> 00:24:30,390 and the way they do that is 478 00:24:30,469 --> 00:24:33,700 to utilize the shear in the atmosphere. 479 00:24:33,772 --> 00:24:36,605 Freeman: Michael's kite requires two forces 480 00:24:36,675 --> 00:24:38,404 to stay aloft and stable - 481 00:24:38,477 --> 00:24:40,877 wind to lift the kite, 482 00:24:40,946 --> 00:24:44,973 and an anchor to keep it from blowing ever upward. 483 00:24:45,050 --> 00:24:48,383 The alien kite plant works much the same way. 484 00:24:48,453 --> 00:24:52,321 So, what we've posited for this particular plant is 485 00:24:52,390 --> 00:24:54,915 a lifting surface on one end of the string, 486 00:24:54,993 --> 00:24:57,120 and at the other end of the string, 487 00:24:57,195 --> 00:25:00,062 something that functions like a parachute 488 00:25:00,131 --> 00:25:02,463 that produces a drag force. 489 00:25:02,534 --> 00:25:04,764 And because the wind changes with altitude, 490 00:25:04,836 --> 00:25:07,304 they're moving at different speeds. 491 00:25:07,372 --> 00:25:10,671 You then get a lift force that keeps the kite up 492 00:25:10,742 --> 00:25:12,539 and it pulls on the drag chute, 493 00:25:12,611 --> 00:25:14,909 but that keeps the tension on the string 494 00:25:14,980 --> 00:25:17,471 and the whole system is stable. 495 00:25:17,549 --> 00:25:19,608 Freeman: Sounds unlikely? 496 00:25:19,684 --> 00:25:21,948 Michael doesn't think so. 497 00:25:22,020 --> 00:25:25,012 Years of studying organisms on Earth has convinced him 498 00:25:25,090 --> 00:25:29,618 that life would evolve to suit any environment. 499 00:25:29,694 --> 00:25:32,663 Labarbera: Evolution goes through very strange pathways 500 00:25:32,731 --> 00:25:34,130 to get to an endpoint. 501 00:25:34,199 --> 00:25:35,962 This particular one, 502 00:25:36,034 --> 00:25:39,060 we don't have an example here on Earth, 503 00:25:39,137 --> 00:25:42,834 but on the planet posited here 504 00:25:42,908 --> 00:25:45,570 with low solar input for the ground level 505 00:25:45,644 --> 00:25:47,043 and a high wind shear, 506 00:25:47,112 --> 00:25:49,706 it's entirely possible that it could function. 507 00:25:49,781 --> 00:25:53,308 Freeman: Closer to the surface of Gliese 581D, 508 00:25:53,385 --> 00:25:56,513 the once bright sunlight dims 509 00:25:56,588 --> 00:26:00,024 as this exoplanet enters a permanent, hazy twilight. 510 00:26:00,091 --> 00:26:02,855 The atmosphere is thick and murky, 511 00:26:02,928 --> 00:26:05,089 but warm enough to sustain life. 512 00:26:05,163 --> 00:26:08,394 In fact, Michael Labarbera speculates 513 00:26:08,466 --> 00:26:10,866 that it could host a thriving ecosystem 514 00:26:10,936 --> 00:26:13,700 of hunters and prey. 515 00:26:13,772 --> 00:26:16,741 What kind of predator would evolve here? 516 00:26:16,808 --> 00:26:21,040 An aerial hunter - thin-winged and bat-like, 517 00:26:21,112 --> 00:26:26,015 but able to soar and glide for days like an albatross. 518 00:26:26,084 --> 00:26:28,678 A... bat-atross? 519 00:26:28,753 --> 00:26:30,186 Labarbera: Now, this animal, 520 00:26:30,255 --> 00:26:33,315 because the atmosphere is relatively opaque, 521 00:26:33,391 --> 00:26:36,656 has to be able to travel long distances at minimal cost 522 00:26:36,728 --> 00:26:38,355 in order to find their prey. 523 00:26:38,430 --> 00:26:39,761 It's got long wings. 524 00:26:39,831 --> 00:26:43,733 It's got relatively narrow wings because they're more efficient. 525 00:26:43,802 --> 00:26:46,896 It has a big wing area relative to its body. 526 00:26:46,972 --> 00:26:48,530 Freeman: On Earth, 527 00:26:48,607 --> 00:26:52,566 albatrosses use a technique called dynamic soaring 528 00:26:52,644 --> 00:26:55,078 to travel thousands of miles 529 00:26:55,146 --> 00:26:57,637 while barely flapping their wings. 530 00:26:57,716 --> 00:26:59,650 Gliding in long loops, 531 00:26:59,718 --> 00:27:03,415 the bat-atross would also conserve energy 532 00:27:03,488 --> 00:27:06,514 by letting air currents carry it along. 533 00:27:06,591 --> 00:27:10,527 Labarbera: The animal actually covers many times the distance 534 00:27:10,595 --> 00:27:13,393 in these loops that it's covering on the ground, 535 00:27:13,465 --> 00:27:14,796 but it doesn't matter. 536 00:27:14,866 --> 00:27:17,300 It doesn't cost it anything. It's free. 537 00:27:17,369 --> 00:27:20,497 It's energy that's supplied by the environment, 538 00:27:20,572 --> 00:27:21,937 not by the organism. 539 00:27:22,007 --> 00:27:25,807 Freeman: But how, in a world of permanent twilight, 540 00:27:25,877 --> 00:27:29,108 does this hunter find its prey? 541 00:27:29,180 --> 00:27:30,579 In the absence of light, 542 00:27:30,649 --> 00:27:33,049 there's got to be some other way of locating prey. 543 00:27:33,118 --> 00:27:34,949 One way is just to sit and listen 544 00:27:35,020 --> 00:27:37,011 and wait for your prey to make noise. 545 00:27:37,088 --> 00:27:39,079 The other way is for you to make noise 546 00:27:39,157 --> 00:27:41,591 and listen for echoes - what we call sonar. 547 00:27:41,660 --> 00:27:43,992 So that you send a sound beam out 548 00:27:44,062 --> 00:27:45,256 and you wait for a reflection. 549 00:27:45,330 --> 00:27:47,195 I can get a lot of information 550 00:27:47,265 --> 00:27:52,066 from the response of the ball as it comes back. 551 00:27:52,137 --> 00:27:55,004 So, the delay between when I throw and when it returns 552 00:27:55,073 --> 00:27:58,270 tells me how far away the object is. 553 00:27:58,343 --> 00:28:00,868 If it comes back faster than I threw it out, 554 00:28:00,945 --> 00:28:02,845 then the object is coming towards me. 555 00:28:02,914 --> 00:28:05,075 If it's going in the other direction, 556 00:28:05,150 --> 00:28:07,311 it will come back slower. 557 00:28:07,385 --> 00:28:10,013 If you're looking for prey, this is a wonderful idea, 558 00:28:10,088 --> 00:28:13,057 unless your prey, of course, can detect the sound. 559 00:28:13,124 --> 00:28:16,719 Freeman: The bat-atross would be an effective killer, 560 00:28:16,795 --> 00:28:21,459 so its prey would need to develop effective defenses. 561 00:28:21,533 --> 00:28:24,024 William Bains imagines an animal 562 00:28:24,102 --> 00:28:26,832 similar to the hard-shelled marine life 563 00:28:26,905 --> 00:28:28,395 that evolved on Earth 564 00:28:28,473 --> 00:28:30,668 hundreds of millions of years ago. 565 00:28:30,742 --> 00:28:32,801 Bains: The nautilus is natural prey for the hunters, 566 00:28:32,877 --> 00:28:34,902 and they'll have three defense mechanisms. 567 00:28:34,979 --> 00:28:36,970 First is, of course, they have a shell. 568 00:28:37,048 --> 00:28:39,380 The second is if you're being hunted by sonar, 569 00:28:39,451 --> 00:28:42,113 then you develop very good ears so you can hear sonar. 570 00:28:42,187 --> 00:28:45,554 When you hear the ping of a sonar, you run for it. 571 00:28:45,623 --> 00:28:47,386 And it has a jet propulsion system 572 00:28:47,459 --> 00:28:50,326 that can squirt itself forward in emergencies. 573 00:28:50,395 --> 00:28:51,862 These guys will be able to 574 00:28:51,930 --> 00:28:54,091 jet themselves through the atmosphere 575 00:28:54,165 --> 00:28:56,224 in short bursts, moving very quickly. 576 00:28:56,301 --> 00:28:57,495 So, at the last minute, 577 00:28:57,569 --> 00:28:59,969 they'll jet to one side and escape being eaten. 578 00:29:00,038 --> 00:29:03,474 Freeman: But even with these defenses, 579 00:29:03,541 --> 00:29:06,567 the bat-atross would be a fearsome opponent, 580 00:29:06,644 --> 00:29:09,340 and the nautilus won't always get away. 581 00:29:11,516 --> 00:29:13,143 Labarbera: It's life on the edge. 582 00:29:13,218 --> 00:29:15,311 There always is a top predator. 583 00:29:15,386 --> 00:29:17,013 It's the rarest animal, 584 00:29:17,088 --> 00:29:19,989 but it's not the guy you want to meet in a dark alley. 585 00:29:20,058 --> 00:29:24,757 Freeman: Brutal conditions breed brutal life-forms. 586 00:29:24,829 --> 00:29:27,423 Here on Earth, over hundreds of millions of years, 587 00:29:27,499 --> 00:29:29,763 billions of different creatures competed for survival, 588 00:29:29,834 --> 00:29:34,237 but eventually, a special mutation enabled one animal 589 00:29:34,305 --> 00:29:37,138 to become the planet's top predator. 590 00:29:37,208 --> 00:29:41,269 That mutation was the human brain. 591 00:29:41,346 --> 00:29:43,405 Somewhere out in space, 592 00:29:43,481 --> 00:29:46,882 alien evolution should have created beings 593 00:29:46,951 --> 00:29:49,476 at least as smart as we are. 594 00:29:49,554 --> 00:29:53,251 What do intelligent extraterrestrials look like? 595 00:29:53,324 --> 00:29:56,122 This man thinks he knows, 596 00:29:56,194 --> 00:30:00,392 and the answer could be bad news for life on Earth. 597 00:30:05,503 --> 00:30:08,336 With each new world we discover, 598 00:30:08,406 --> 00:30:11,432 we come one step closer to finding evidence 599 00:30:11,509 --> 00:30:12,942 of life beyond Earth 600 00:30:13,011 --> 00:30:16,310 and perhaps to fulfilling our dreams 601 00:30:16,381 --> 00:30:19,646 of communicating with alien life-forms. 602 00:30:19,717 --> 00:30:22,277 But if that day ever comes, 603 00:30:22,353 --> 00:30:25,049 we'd better brace ourselves for a shock, 604 00:30:25,123 --> 00:30:27,921 because many scientists think 605 00:30:27,992 --> 00:30:31,484 they may not look like living beings at all. 606 00:30:31,563 --> 00:30:35,055 For the past 50 years, 607 00:30:35,133 --> 00:30:39,035 the search for extra-terrestrial intelligence, SETI, 608 00:30:39,103 --> 00:30:42,504 has attempted to capture any glimmer of communication 609 00:30:42,574 --> 00:30:45,668 from alien worlds. 610 00:30:45,743 --> 00:30:48,803 For Seth Shostack, SETI's senior astronomer, 611 00:30:48,880 --> 00:30:51,872 it's a search for our distant cosmic image, 612 00:30:51,950 --> 00:30:57,013 for a species with a brain at least as smart as ours. 613 00:30:57,088 --> 00:30:58,146 When it comes to intelligent life, 614 00:30:58,223 --> 00:30:59,383 we haven't found it. 615 00:30:59,457 --> 00:31:01,482 So, there are people on all sides of the issue. 616 00:31:01,559 --> 00:31:03,584 But the one thing that can convince you - 617 00:31:03,661 --> 00:31:06,152 I think can convince anybody - is that even if you think 618 00:31:06,231 --> 00:31:08,859 the processes that could lead to life, 619 00:31:08,933 --> 00:31:10,264 lead to intelligent life, 620 00:31:10,335 --> 00:31:13,202 are not going to occur very often, 621 00:31:13,271 --> 00:31:16,399 there's so many chances for it to happen in the cosmos, 622 00:31:16,474 --> 00:31:17,771 it would be miraculous 623 00:31:17,842 --> 00:31:20,709 if we were the only world with intelligent beings. 624 00:31:20,778 --> 00:31:23,008 Freeman: Humans aren't the largest 625 00:31:23,081 --> 00:31:24,810 or the fastest 626 00:31:24,883 --> 00:31:28,148 or the most agile animals on Earth, 627 00:31:28,219 --> 00:31:30,687 but we are the smartest. 628 00:31:30,755 --> 00:31:33,019 Our brains have put us on top. 629 00:31:33,091 --> 00:31:35,719 There is, however, plenty of room for improvement. 630 00:31:35,793 --> 00:31:38,193 There's an unavoidable tendency to think 631 00:31:38,263 --> 00:31:40,731 that we're kind of the crown of creation. 632 00:31:40,798 --> 00:31:41,765 This is it. 633 00:31:41,833 --> 00:31:43,494 You know, 4 billion years of evolution 634 00:31:43,568 --> 00:31:45,502 from the beginnings of life to us. 635 00:31:45,570 --> 00:31:47,333 You know, I think if you asked the dinosaurs 636 00:31:47,405 --> 00:31:48,531 the same question - 637 00:31:48,606 --> 00:31:50,073 "Do you think you're the crown of creation?" 638 00:31:50,141 --> 00:31:51,608 I bet they would have said "Yes," 639 00:31:51,676 --> 00:31:52,768 if they could have talked. 640 00:31:52,844 --> 00:31:54,709 "This is it. This is the end of evolution." 641 00:31:54,779 --> 00:31:55,803 Well, they were wrong. 642 00:31:55,880 --> 00:31:57,438 And it would be wrong for us to think 643 00:31:57,515 --> 00:31:59,415 we're the end of evolution, too, obviously. 644 00:31:59,484 --> 00:32:03,011 Freeman: So, where will evolution take us next? 645 00:32:03,087 --> 00:32:06,523 And where is it likely to have taken alien civilizations? 646 00:32:06,591 --> 00:32:11,221 Seth thinks we need to look at our computers for the answer. 647 00:32:11,296 --> 00:32:12,695 Since the 1970s, 648 00:32:12,764 --> 00:32:14,994 when floppy disks were the gold standard, 649 00:32:15,066 --> 00:32:18,502 this speed at which computers process instructions 650 00:32:18,569 --> 00:32:22,027 has increased more than 100,000 times. 651 00:32:22,106 --> 00:32:24,574 Today, for $1,000, you can buy a computer 652 00:32:24,642 --> 00:32:27,839 that has, if you will, the thinking capability - 653 00:32:27,912 --> 00:32:30,904 or at least the computational capability of a lizard. 654 00:32:30,982 --> 00:32:32,210 Not so interesting. 655 00:32:32,283 --> 00:32:36,913 But by 2020 or 2025, $1,000 will buy you a laptop 656 00:32:36,988 --> 00:32:41,015 that has the same computational power as a human brain. 657 00:32:41,092 --> 00:32:44,027 Freeman: The IQs of artificial brains 658 00:32:44,095 --> 00:32:46,359 are going from zero to 200 659 00:32:46,431 --> 00:32:49,229 in the historic blink of an eye. 660 00:32:49,300 --> 00:32:53,100 How would a similar trajectory play out 661 00:32:53,171 --> 00:32:58,575 on a planet that is a mere 500 years ahead of us? 662 00:32:58,643 --> 00:33:00,702 The interesting thing about artificial intelligence, 663 00:33:00,778 --> 00:33:02,769 of course, is its pace of evolution. 664 00:33:02,847 --> 00:33:04,474 I mean, we're stuck with Darwinian evolution, 665 00:33:04,549 --> 00:33:05,880 but the machines wouldn't be. 666 00:33:05,950 --> 00:33:08,748 What it means is that if you develop a thinking machine, 667 00:33:08,820 --> 00:33:11,345 it's going to improve itself very, very quickly. 668 00:33:11,422 --> 00:33:15,654 Freeman: In 1948, mathematician John Von Neumann 669 00:33:15,727 --> 00:33:18,127 imagined a machine so intelligent 670 00:33:18,196 --> 00:33:21,063 it could make copies of itself. 671 00:33:21,132 --> 00:33:24,124 Each copy would improve on the previous model, 672 00:33:24,202 --> 00:33:27,797 much as nature continually improves on its designs. 673 00:33:27,872 --> 00:33:30,841 But this machine's evolution would take place much faster 674 00:33:30,908 --> 00:33:33,376 than biological evolution. 675 00:33:33,444 --> 00:33:38,006 Today, Von Neumann machines exist in crude form. 676 00:33:38,082 --> 00:33:41,813 On a planet more advanced than our own, 677 00:33:41,886 --> 00:33:44,354 could they be the most intelligent life-form, 678 00:33:44,422 --> 00:33:46,982 the dominant life-form? 679 00:33:47,058 --> 00:33:48,821 Will our first contact be 680 00:33:48,893 --> 00:33:52,260 with a race of super-intelligent machines? 681 00:33:52,330 --> 00:33:54,389 You're only gonna hear from a species 682 00:33:54,465 --> 00:33:56,490 that's at least as clever as we are. 683 00:33:56,567 --> 00:33:59,092 So, what are the odds that they're within 50 or 100 years 684 00:33:59,170 --> 00:34:00,398 of our level of development? 685 00:34:00,471 --> 00:34:01,631 Pretty slim. 686 00:34:01,706 --> 00:34:03,435 They're likely to be thousands, millions, 687 00:34:03,508 --> 00:34:06,136 maybe even more years ahead of us. 688 00:34:06,210 --> 00:34:08,110 So, if you think about that for a moment, 689 00:34:08,179 --> 00:34:10,147 you recognize that if we do find a signal, 690 00:34:10,214 --> 00:34:11,476 the odds are pretty good 691 00:34:11,549 --> 00:34:14,575 that that signal's coming from artificial intelligence, 692 00:34:14,652 --> 00:34:17,985 not some soft, squishy, little gray guy with big eyeballs. 693 00:34:18,056 --> 00:34:20,081 Freeman: On some distant planet, 694 00:34:20,158 --> 00:34:24,322 the book of life may no longer contain any biological forms. 695 00:34:24,395 --> 00:34:27,762 And if mechanical life has enough power, 696 00:34:27,832 --> 00:34:31,734 there's no limit to how large or complex it can become. 697 00:34:31,803 --> 00:34:33,896 Shostack: Or maybe they've reorganized themselves 698 00:34:33,971 --> 00:34:36,496 so that they can share the thinking load 699 00:34:36,574 --> 00:34:38,872 amongst many members of the species, 700 00:34:38,943 --> 00:34:40,911 like distributed processing with computers. 701 00:34:40,978 --> 00:34:43,139 I mean, why should the aliens be content 702 00:34:43,214 --> 00:34:45,341 to be stuck with a kind of intelligence 703 00:34:45,416 --> 00:34:47,509 that can fit inside their heads? 704 00:34:51,089 --> 00:34:53,148 Freeman: Alien evolution 705 00:34:53,224 --> 00:34:55,749 could produce a living machine planet 706 00:34:55,827 --> 00:34:57,920 throbbing with the combined intelligence 707 00:34:57,995 --> 00:34:59,963 of billions of alien minds. 708 00:35:00,031 --> 00:35:04,593 If such advanced life exists, how would we spot it? 709 00:35:04,669 --> 00:35:06,864 And should we even want to? 710 00:35:06,938 --> 00:35:09,463 Will aliens welcome us as friends 711 00:35:09,540 --> 00:35:11,337 or view us as threats? 712 00:35:11,409 --> 00:35:15,345 Or perhaps see Earth as a world to conquer? 713 00:35:15,413 --> 00:35:17,745 We wonder what aliens look like, 714 00:35:17,815 --> 00:35:20,147 but what do we look like to them? 715 00:35:20,218 --> 00:35:23,847 This woman has put herself inside their heads, 716 00:35:23,921 --> 00:35:27,550 and she believes she has the answer. 717 00:35:32,930 --> 00:35:36,457 As long as humans have looked up at the night sky, 718 00:35:36,534 --> 00:35:40,026 we have wondered whether something or someone out there 719 00:35:40,104 --> 00:35:42,368 is looking back. 720 00:35:42,440 --> 00:35:45,773 We want to know what aliens look like. 721 00:35:45,843 --> 00:35:49,677 What do we look like to aliens? 722 00:35:49,747 --> 00:35:53,183 If there is intelligent life out there, 723 00:35:53,251 --> 00:35:57,449 does the Earth look like a place worth visiting? 724 00:35:57,522 --> 00:36:00,923 May 29, 2008. 725 00:36:00,992 --> 00:36:04,120 31 million miles out in space, 726 00:36:04,195 --> 00:36:06,925 the eyes of a technologically advanced race 727 00:36:06,998 --> 00:36:10,365 scan our planet for the signatures of life. 728 00:36:10,434 --> 00:36:13,926 Not aliens, but this was still a close encounter 729 00:36:14,005 --> 00:36:16,303 of an extraordinary kind. 730 00:36:16,374 --> 00:36:19,138 It was the NASA space probe Epoxi. 731 00:36:19,210 --> 00:36:22,737 Sent out to get closeups of comets, 732 00:36:22,813 --> 00:36:26,010 Epoxi briefly turned its lens back to its mother planet. 733 00:36:26,083 --> 00:36:27,880 And for the first time, 734 00:36:27,952 --> 00:36:31,319 we saw the Earth as aliens might see us. 735 00:36:40,131 --> 00:36:44,830 Astrophysicist Sara Seager was part of the Epoxi team. 736 00:36:44,902 --> 00:36:47,200 Sara normally studies exoplanets, 737 00:36:47,271 --> 00:36:48,568 looking for clues 738 00:36:48,639 --> 00:36:51,130 about alien atmospheres and ecosystems. 739 00:36:51,209 --> 00:36:54,178 The Epoxi probe gave her the chance to find out 740 00:36:54,245 --> 00:36:58,204 what Earth might look like to an alien astronomer. 741 00:36:58,282 --> 00:36:59,613 If you pretend you know nothing about Earth, 742 00:36:59,684 --> 00:37:01,015 what could you learn about Earth? 743 00:37:01,085 --> 00:37:04,316 An alien would be able to pick out Earth's rotation rate. 744 00:37:04,388 --> 00:37:05,650 They would be able to notice 745 00:37:05,723 --> 00:37:08,214 that we have surfaces of very different reflectivity - 746 00:37:08,292 --> 00:37:09,589 that's cloud, land, and ocean. 747 00:37:09,660 --> 00:37:11,685 And they could also see that we have weather. 748 00:37:11,762 --> 00:37:13,389 They would see variability 749 00:37:13,464 --> 00:37:16,297 that isn't related to the rotation rate of Earth. 750 00:37:16,367 --> 00:37:19,200 The second thing Epoxi did was look at a spectrum of Earth - 751 00:37:19,270 --> 00:37:20,464 that is, take the white light 752 00:37:20,538 --> 00:37:22,335 and split it up into the different colors 753 00:37:22,406 --> 00:37:24,840 and to check and see if any of those colors were missing. 754 00:37:24,909 --> 00:37:26,774 We call that a spectrum. 755 00:37:26,844 --> 00:37:29,938 Freeman: The spectrum of Earth's colors 756 00:37:30,014 --> 00:37:31,413 are like a flag 757 00:37:31,482 --> 00:37:33,973 announcing the presence of life on our planet. 758 00:37:34,051 --> 00:37:37,020 The blue of the oceans, the white of the clouds, 759 00:37:37,088 --> 00:37:38,419 the green of the land 760 00:37:38,489 --> 00:37:42,323 are all markers of an active ecosystem. 761 00:37:42,393 --> 00:37:45,157 Seager: If an alien is looking back at us from far away, 762 00:37:45,229 --> 00:37:46,253 the aliens would see 763 00:37:46,330 --> 00:37:47,797 that we have oxygen in the atmosphere. 764 00:37:47,865 --> 00:37:50,698 In fact, our atmosphere has 20% oxygen by volume. 765 00:37:50,768 --> 00:37:53,134 What's so fascinating is that, without life, 766 00:37:53,204 --> 00:37:57,004 our Earth would have basically 10 billion times less oxygen. 767 00:37:57,074 --> 00:37:59,542 So, oxygen would be essentially non-existent on Earth. 768 00:37:59,610 --> 00:38:01,510 And oxygen on Earth is created by life, 769 00:38:01,579 --> 00:38:04,446 so those aliens would know that oxygen in such large quantities 770 00:38:04,515 --> 00:38:05,914 should not be in our atmosphere 771 00:38:05,983 --> 00:38:08,213 unless it is being continually produced by something. 772 00:38:08,286 --> 00:38:10,914 And nothing that we know of in geophysics 773 00:38:10,988 --> 00:38:12,649 can produce so much oxygen. 774 00:38:12,723 --> 00:38:14,350 And that's why we attribute it to life. 775 00:38:14,425 --> 00:38:18,589 Freeman: Aliens might see that our planet supports life, 776 00:38:18,663 --> 00:38:20,893 but they might not see 777 00:38:20,965 --> 00:38:23,399 that Earth is technologically advanced. 778 00:38:23,467 --> 00:38:25,765 They would have to look carefully 779 00:38:25,836 --> 00:38:28,669 to detect things like atmospheric pollution 780 00:38:28,739 --> 00:38:31,867 or the heat signatures of our cities. 781 00:38:31,942 --> 00:38:33,773 Reading the colors of our world 782 00:38:33,844 --> 00:38:37,109 and the millions of others like it out in the Universe 783 00:38:37,181 --> 00:38:40,116 would be easy for an advanced alien civilization. 784 00:38:40,184 --> 00:38:43,984 Unfortunately, it is not yet easy for us. 785 00:38:44,055 --> 00:38:46,148 Spotting exoplanets 786 00:38:46,223 --> 00:38:49,124 pushes the limits of current technology. 787 00:38:49,193 --> 00:38:53,220 If we want to see colors, we need a new set of tools. 788 00:38:55,232 --> 00:38:57,530 Astrophysicist Dimitar Sasselov 789 00:38:57,601 --> 00:38:59,728 wants to do something about that. 790 00:38:59,804 --> 00:39:04,002 Sheila: These are little round planets. 791 00:39:04,075 --> 00:39:08,409 I'm gonna just drop a few on to show transiting planets. 792 00:39:08,479 --> 00:39:10,845 I guess there's two transiting. 793 00:39:10,915 --> 00:39:15,511 Dimitar's wife, Sheila, paints scenes of deep space 794 00:39:15,586 --> 00:39:20,819 inspired by his research on the Kepler planet-finding probe. 795 00:39:20,891 --> 00:39:24,987 This is the kind of thing we want to discover with Kepler. 796 00:39:25,062 --> 00:39:28,395 A transiting planet, and there is a moon around it. 797 00:39:28,466 --> 00:39:29,831 That would be great. 798 00:39:29,900 --> 00:39:31,868 So, there it is. 799 00:39:31,936 --> 00:39:36,396 That's the planet with life on it - right here. 800 00:39:36,474 --> 00:39:37,634 We have a big problem. 801 00:39:37,708 --> 00:39:41,269 This challenge relates to our inability to measure 802 00:39:41,345 --> 00:39:44,178 the colors of the star or the planets separately 803 00:39:44,248 --> 00:39:46,216 to very high precision. 804 00:39:46,283 --> 00:39:49,878 And the challenge is about the factor of 10 to 100 805 00:39:49,954 --> 00:39:52,582 beyond what current technology works. 806 00:39:52,656 --> 00:39:55,523 Freeman: The biggest barrier we have 807 00:39:55,593 --> 00:39:57,788 to seeing the colors of other planets 808 00:39:57,862 --> 00:40:00,729 is something every photographer has run into - 809 00:40:00,798 --> 00:40:03,062 camera shake. 810 00:40:03,134 --> 00:40:05,034 If you take a picture in the dark, 811 00:40:05,102 --> 00:40:07,036 you need as much light as possible, 812 00:40:07,104 --> 00:40:10,005 which means you can't move the camera 813 00:40:10,074 --> 00:40:12,042 or you'll get a blurry image. 814 00:40:12,109 --> 00:40:15,875 Earth-like planets are so small and so far away 815 00:40:15,946 --> 00:40:20,144 that their images only fill one thousandth of a single pixel 816 00:40:20,217 --> 00:40:22,242 of a digital camera. 817 00:40:22,319 --> 00:40:25,049 If that pixel moves even slightly, 818 00:40:25,122 --> 00:40:28,182 the camera shake will ruin the picture. 819 00:40:28,259 --> 00:40:32,195 But how can you possibly keep one pixel perfectly still 820 00:40:32,263 --> 00:40:34,493 over the days and years it takes 821 00:40:34,565 --> 00:40:37,398 to track an object in distant space? 822 00:40:37,468 --> 00:40:41,495 Dimitar's solution is the astro-comb. 823 00:40:41,572 --> 00:40:44,439 It uses lasers to keep a telescope's camera sensor 824 00:40:44,508 --> 00:40:48,842 precisely calibrated over a period of decades. 825 00:40:48,913 --> 00:40:52,007 Sasselov: The astro-comb that you see here 826 00:40:52,082 --> 00:40:54,209 is the technological breakthrough 827 00:40:54,285 --> 00:40:56,583 which was needed to bridge that gap. 828 00:40:56,654 --> 00:41:00,112 Freeman: When we see the true colors of other worlds, 829 00:41:00,191 --> 00:41:04,150 we will know where and how life is distributed 830 00:41:04,228 --> 00:41:06,560 across the Universe. 831 00:41:06,630 --> 00:41:11,033 And the next phase of our quest for alien life will begin. 832 00:41:11,902 --> 00:41:14,097 Where will it take us? 833 00:41:14,171 --> 00:41:17,334 What exciting, new worlds will we see? 834 00:41:17,408 --> 00:41:22,072 What new and unexpected creatures might live on them? 835 00:41:22,146 --> 00:41:26,378 Biologists think that life out there might look earth-like, 836 00:41:26,450 --> 00:41:29,749 but it won't look human. 837 00:41:29,820 --> 00:41:33,984 With so many planets out there, so many chances at life, 838 00:41:34,058 --> 00:41:37,994 we could have human-like relatives on a far-away earth. 839 00:41:38,062 --> 00:41:39,222 Creatures like us, 840 00:41:39,296 --> 00:41:41,526 perhaps as anxious as we are to know 841 00:41:41,599 --> 00:41:43,624 if they are alone in the Universe. 842 00:41:43,701 --> 00:41:49,662 As our tools improve, so do our odds of finding them. 843 00:41:49,740 --> 00:41:53,005 Sasselov: It is clear that we're in a new age 844 00:41:53,077 --> 00:41:55,045 of exploration and discovery. 845 00:41:55,112 --> 00:41:56,841 It hasn't been for 500 years 846 00:41:56,914 --> 00:41:59,348 that people have tried to discover planets 847 00:41:59,416 --> 00:42:00,508 around other stars. 848 00:42:00,584 --> 00:42:02,381 Now we have them. 849 00:42:02,453 --> 00:42:06,719 We have much more to explore, and the best is yet to come. 850 00:42:06,790 --> 00:42:08,382 1,000 years from now, 851 00:42:08,459 --> 00:42:10,825 when people look back at our generation and ask, 852 00:42:10,895 --> 00:42:13,386 "What are the biggest accomplishments?" 853 00:42:13,464 --> 00:42:16,194 I like to think of these people making interstellar journeys 854 00:42:16,267 --> 00:42:17,666 and looking back and thinking 855 00:42:17,735 --> 00:42:19,532 we were the ones who started it all. 856 00:42:19,603 --> 00:42:23,869 Freeman: What do aliens look like? 857 00:42:23,941 --> 00:42:26,705 What are the limits of our imagination? 858 00:42:26,777 --> 00:42:28,904 The true face of an alien 859 00:42:28,979 --> 00:42:32,506 will probably defy our scientific speculations. 860 00:42:32,583 --> 00:42:35,074 But our efforts won't be wasted, 861 00:42:35,152 --> 00:42:38,610 even if we do get all the details wrong. 862 00:42:38,689 --> 00:42:42,250 Our eternal intrigue about alien life 863 00:42:42,326 --> 00:42:44,453 and our persistent fear of it 864 00:42:44,528 --> 00:42:47,258 both rise from the same source - 865 00:42:47,331 --> 00:42:50,562 the quest to understand our place 866 00:42:50,634 --> 00:42:54,661 in the family of life-forms that populate the cosmos. 867 00:42:54,738 --> 00:42:56,706 Know that, 868 00:42:56,774 --> 00:42:59,766 and we'll know the destiny of humankind.