The Possibility of Life

The Search for Alien Life and SETI

• Scientists who scan the sky for alien signals seem to always expect an answer within the next ten to twenty-five years, whether they’re postulating from 1980 or 2023.
• Walker and Cronin’s approach doesn’t require any specific chemistry. And indeed, the search for life beyond Earth can seem painfully narrow, sometimes—searching for water, searching for carbon, searching for temperatures and conditions so like those we know here. There are two ways to justify this. First, that this chemistry may truly be the best chemistry for life. Second, that this is the only kind of life we’d know how to look for. You have to start somewhere.
• One of the most talked-about possible homes for life, right within our solar system, is Titan, Saturn’s large and largest moon, where you’ll find the only other open oceans around the sun. But they’re not filled with water. They’re oceans of methane and ethane, substances that are gases on Earth but are liquid at Titan’s frigid surface temperatures (−290° Fahrenheit, or –180º Celsius, or so). And some scientists think they could be home to life. Life on Titan would be as un-Earthlike as its environment. Planetary scientist Morgan Cable, who oversees NASA’s Astrobiology and Ocean Worlds research group, told me that Titan’s lakes are exciting largely because surface liquid is so rare in the solar system. Titan also has an underground ocean of liquid water, probably salty or shot through with ammonialike antifreeze, which is another possible home for life.
• Are planets like Earth common or rare? Rocky and wet, with enough gravity to hold an atmosphere but not so much as to crush a body, with seasons, with a moon... How long is the list of requirements for what we consider Earthlike, and are those the same as the requirements for life? Understanding the different kinds of planets that may be out there leads us to ask: On how weird of a world could life flourish?
• When I asked astronomer Jessie Christiansen, science lead at the NASA Exoplanet Archive, what’s happening inside her imagination when she’s thinking about an exoplanet, she told me she basically outsources that work to collaborators, artists who create the images that go along with press releases announcing the discovery of new exoplanets. Christiansen said, “I bring them the numbers—it’s this big, it weighs this much, and the star is this temperature. And then...they make something.” These artists are the ones who turn the place an astronomer can understand into one the public can imagine their way onto. So I asked the artists how they do that. Collaborators Tim Pyle and Robert Hurt came to the work from opposite poles. Hurt is an astronomer who had always dabbled in graphic design and art, and Pyle worked for years in visual effects in Hollywood and applied for his current job at Caltech with an animated short about bees taking over some NASA equipment and exploring space. Their work is far broader than creating art to accompany press releases—they craft visuals and videos and multimedia experiences, any way of “telling the science story”—but their illustrations of exoplanets are no small part of their project. These images, which often accompany news stories about the newly discovered exoplanets, have to draw readers in, to set up their framework for the story they’re about to read. Pyle says, “It has to be attractive on some level—in the sense of being eye-catching... It can be a very ugly planet that’s attractive,” a cosmic jolie laide. Hurt says, “We need to show them a picture that’s at least starting to be as cool as what you saw on the Guardians of the Galaxy trailer, if we want people to stop and linger and wonder what it was.”
• Abel Méndez, professor of physics and astrobiology at the University of Puerto Rico at Arecibo, maintains a catalog of habitable exoplanets. “The criteria is basically the size and the orbit,” he told me. “That’s it.” The orbit accounts for the temperature, and the size of the planet dictates if its surface can hold liquid water. Méndez said that a planet with 1.5 times Earth’s radius would have about 1 percent of the planet’s mass as atmosphere. Earth’s atmosphere, in comparison, is one-billionth of its mass. “At the surface level the pressure will be so high,” he said, “that it will make any ocean, any liquid water, solid.” On the other hand, if a planet is too small, its weak gravity means it will have no atmosphere or one too thin, and all the water will sublimate and escape into space. This is why Mars, half the size of Earth, may have once had water but lost it.
• Only about 7 percent of stars in the galaxy are like our sun. There are far more red dwarfs out there—small, cool stars that burn for trillions of years longer than their hotter cousins. And odds are, most of them have planets (Earth III would be one of them). Their habitable zones can be measured, too, but while you’d be warm enough for water there on a close orbit, these stars are more active than our sun. Do their intense ultraviolet rays keep any planets near them sterile, or does life, you know, find a way?
• Exomoons may be habitable worlds themselves, or they may make life on their planets possible, stabilizing their orbits and quickening their crusts.
• But the question What could a distant observer see of Earth? contains within it another, more exciting question: Who are we imagining doing the observing? Inherently, it’s someone who wonders if we are here. All of these approaches imagine a distant observer at some unspecified place, far enough away from the Earth to see it as a single point. Lisa Messeri calls this imagined distant location an Archimedean point
• Sagan agreed that alien life was probably incomprehensible. He wrote in Cosmos that even if extraterrestrial life shared our biochemistry, it would have no reason to look at all like life on Earth. But—twist his arm!—he deigned to conjure an example, picking a planetary environment that seemed uninhabitable to more conservative minds, a gas giant like Jupiter. That planet has no solid surface, just a dense atmosphere of hydrogen, helium, methane, and ammonia, where “organic molecules may be falling from the skies like manna from heaven.” Sagan proposed life-forms he called floaters, organic balloons, whale-sized or larger, pumping themselves full of hydrogen or hot gas to rise or sink as needed.
• The Golden Record is the richest message humanity has sent into the cosmos, devised by a committee led by Carl Sagan over the course of a few months. Its cover contains clues to its origins—the pulsar map—and instructions for playing the record, converting the etched grooves on its surface into images and sound. The images include scientific diagrams and photographs, of the Arecibo telescope, of a mother breastfeeding, of a woman standing in front of a supermarket produce display, eating a grape she likely hasn’t yet paid for. The sounds include over two dozen works of music (including Bach, Javanese gamelan, and Chuck Berry), greetings in fifty-five languages, and recordings of thunder, wind, trains, automobiles, heartbeats, and whalesong. There’s also an hour-long recording of Ann Druyan’s brainwaves, taken as she meditated on the history of humanity, its current struggles, and “a personal statement of what it was like to fall in love.”
• The fear that complex cells might be rare came to me from the pretty pessimistic book Rare Earth. The 2000 bestseller leaned all the way into odds and probabilities, making the case that the emergence of complex life is incredibly unlikely—Earths as planets are probably not rare, the authors supposed and research has since borne out. But plant-and-animal-covered Earths, intelligent-species-inhabited Earths? Those, the authors argue, may indeed be one-in-a-cosmos.
• Dyson spheres are named for Freeman Dyson, the physicist, mathematician, and general polymath. While most SETI scientists in the early 1960s were looking for extraterrestrial beacons, Dyson thought “one ought to be looking at the uncooperative society.” Not obstinate, just not actively trying to help us. “The idea of searching for radio signals was a fine idea,” he said in a 1981 interview, “but it only works if you have some cooperation at the other end. So I was always thinking about what to do if you were looking just for evidence of intelligent activities without anything in the nature of a message.” And you might as well start with the easiest technology to detect—the biggest or brightest. So the massive spheres Dyson popularized in his 1960 paper were the result of him asking What is the largest feasible technology?
• This assumption was part of Sagan’s argument for the necessity of SETI. In 1979 he wrote, “The existence of a single message from space will show that it is possible to live through technological adolescence: the civilization transmitting the message, after all, has survived.” He hoped that such proof would be galvanizing for humanity, an answer to pessimists who believed self-destruction loomed.
• He found that in order for our civilization to be the first in the galaxy, the odds of a technological civilization evolving on a habitable planet would have to be less than 1 in 1024, or one in one thousand billion trillion.

Evolution and Convergence

• The moon also gives us our tides, stronger and more variable than they would be from the sun alone. And tides may have shaped evolution on Earth, Rebecca Boyle writes in Scientific American, “shepherding the first plants and tetrapods [four-legged animals] from the salty marshes of the coasts and onto land.” The ability to survive in tidal zones, sometimes submerged and sometimes dry, encouraged sea creatures to evolve toward land-dwelling.
• If you’re going to not only invent an alien creature but also depict its evolutionary context, “... it’s actually really easy to just talk to someone for five minutes and get an accurate scientific take on something. It gives you that extra layer of realism.” Even for a lay audience, scientific accuracy is one way to trigger that subconscious click, that sense that this is something real and alive.
• Not every Earth animal with wings or a lensed eye evolved from a common winged or eyed ancestor; these animals stumbled into the same biological solutions to problems like flight and vision. Whales evolved fishlike features but are no more closely related to fish than cows are.
• Would this happen on another planet, too? Not just a convergence of that planet’s common forms but on forms that are common to all planets? Let’s assume (big assumption) this other planet has land and water like we do, as well as maybe even plants and animals (though, even those categories would be a dramatic instance of convergence, hardly to be taken for granted). It seems like it makes sense that any animals that live in the sea would be roughly fish-shaped—it’s a very good body for swimming. On a planet with a transparent atmosphere, light offers a fantastic way to perceive your environment, so these aliens would likely enough see, and eyes have proved on Earth to be the best way to do that. If you have tall plants like trees, why wouldn’t you have animals that swing through their branches? And wouldn’t long limbs and grasping hands, whether four or six or whatever, be good for that? Convergent evolution is so visible on Earth, it seems likely enough that life elsewhere would converge on these efficient forms, too. This is where a billion and a half years of trial and error have gotten us. So the supposition that life on another planet would follow similar forms as on Earth—plants and humanoids and horses and branch-swinging monkeys—isn’t just a lazy fictional gloss.
• In Gould’s camp are biologists who believe that evolution is dependent on so many factors, the flap of butterfly wings as large as an asteroid or as small as a wonky molecule of DNA, that any tiny variation would have sent life in a completely different direction. Evolution, they say, is neither repeatable nor predictable; it is pure, random luck that life here looks as it does. On the other side of the debate are those who are convinced by convergence, who believe it’s an underlying rule of evolution rather than a cool thing to notice about some similar-looking species. Those arguing for convergence think evolution is predictable, that, as one evolutionary biologist puts it, “there are only so many ways to make a living in the world.” These scientists believe that the same forms, proving themselves advantageous, evolve again and again, the best solutions to the challenges nature provides.
• “When [aliens] do finally land on the White House lawn, whatever walks or slithers down the gangplank may look strangely familiar.” And evolutionary biologist Simon Conway Morris said, “The constraints of evolution and the ubiquity of convergence make the emergence of something like ourselves a near-inevitability.” Here on Earth we do have a test case that comes pretty close to another planet: Australia. Marsupials split off from the placental mammals of the rest of the world about 125 million years ago, and Australia has been an island for the last 35 million, cooking up its own species in near isolation. And yet, strange as Australian mammals are when compared to their distant cousins, they also look strikingly familiar.
• But the most popular of these empty-niche thought experiments, Conway Morris writes, is wheels. Wheels are amazing, reducing friction and increasing leverage to push, pull, or propel a load. But no creature on Earth has natural roller skates. There are wheellike structures in biology: the rotary base of a bacterial flagellum, shrimp that curl their entire body into a loop for a few dozen consecutive rolls. But no one uses wheels to get around.
• Natural selection only drives evolution when a system meets three criteria: there is variation within a population or species; the variations affect fitness so that some variants survive or reproduce better than others; and there is an element of genetic heritability, so that variations are passed on to the next generation. While all of these characteristics seem essential to life on Earth, there’s no reason life on another planet would have to be the same.
• That, Losos said, leads to the idea of an entire way of life without species. What if there were no hard boundaries between one animal and another, just “a smear of variation”? Species are taxonomical categories, but their boundaries traditionally correspond to biological lines, across which two organisms can’t reproduce—meaning, for our concerns here, they can’t combine their genes into offspring. But without species boundaries preventing genetic exchange, you’d have a very different range of evolutionary trajectories. “It would certainly make evolution, as a process, very different,” Losos mused. “Would that just be an impediment and make it slower, or might it cause different sorts of evolutionary patterns? I think probably the latter.”
• Mohamed Noor told me that a speciesless planet would actually be more subject to natural selection than life on Earth. “Imagine,” he said, “that something is advantageous. And it spreads through the population of ants.” On Earth, that new adaptation has nothing to offer humans. But a speciesless world is essentially a world without those boundaries—a world all of ants. Not identical, but not separate species, either. “Then it would spread to everything, right?” And the whole planetary population would evolve. In this case, species aren’t outcompeting each other but rather genes are, the advantageous ones dispersing across the whole world.
• Conway Morris’s argument is right in the title of his book, Life’s Solution: Inevitable Humans in a Lonely Universe. We, or something quite like us, were inevitable on Earth due to the forces of evolution. He identifies the likely convergences as “large brain, intelligence, tools, and culture,”which even on Earth are converged upon, evolved into again and again. (See: dolphin, chimpanzee, octopus, crow.) And he thinks that since life elsewhere would be Earthlike, convergently, then from there he feels sure humanlike life will arise on other planets, too.
• The secret of complex life lies in the chimeric nature of the eukaryotic cell—a hopeful monster, born in an improbable merger 2,000 million years ago, an event still frozen in our innermost constitution and dominating our lives today.

Language and Communication

• Dolphins can mimic each other’s whistles pretty effectively, though, and they can’t recognize each other by voice and tone since their voices change with the depth of water—swimming deeper, the greater water pressure raises the pitch of their voice. So instead, they rely on the contour and shape of a whistle.
• Across human abilities and cultures, there are myriad ways in which our sensory capabilities and even our cultures and languages render our subjective experiences of the world incomprehensible to others of our own kind. Some languages have more words for basic colors than others—some naming only dark, white, and red, while others, like Russian, divide blue into light and dark the way English differentiates red from pink. (And because we name dark orange brown, we see it as its own color, where dark blue is just a kind of blue.)
• Jason Wright told me, “My personal best guess is that even if we were to find a communicative transmission, we would not be able to decode it.” He likened it to giving Thomas Edison a modern cable modem and seeing if he could access all the information on the internet.
• But it turns out that the Runa name functions, not objects. Azhawasi is the space enclosed by the unnamed, in Ruanja, flask. “Similarly,” Emilio says, “there is a word for the space we would call a room but no words for wall or for ceiling or floor.” It feels, to an English-speaker, like a suitably alien way of understanding the world. When I see a cup, I see a cup, not the space enclosed by it. I can’t imagine seeing a wall and not having a word for the surface. Ruanja has different declensions for nouns based on whether they are seen or not.
• These feel like unnatural rules to my brain and to the brains of the humans of the novel—but they’re still principles that can be understood and learned. Emilio learns and teaches Ruanja just like he would handle any language on Earth. Russell imagines many forms of convergence between life on Earth and life on Rakhat: plants and animals, predators and prey, laughter and body language and biology. But the fact that Rakhat’s languages can be learned by humans at all, as if they were just particularly strange Earthly tongues, would be its own kind of convergence, momentous for our understanding of aliens and our understanding of the idea of language, both.
• Is human language representative of all language or just how language happens to work here on Earth?
• While adult learners find different languages to be of varying levels of difficulty—due to similarities with their native language, complexity of rules, prevalence of irregular formations, and other factors—children all tend to acquire language within the same time frame. And they do it quickly, without ever really needing to be taught.
• Take two sentences: Mary left, and This made John sad. In that pairing, a single word, This, holds in its reference an entire other sentence. If a single word—in its own sentence, of course—can stand in for a whole sentence, then language can sustain an infinite recursive matryoshka doll of meaning. This infinity isn’t just in scope but innovation. Moro writes, “Humans are the only animals that can recombine discrete elements (words, which obviously include symbolic elements) in such a way as to provide new meaning, depending on how the combination is made.” He likens animals’ vocabularies to “dictionaries of sentences,” fixed and discrete. This is, of course, a difficult assertion to make conclusively—who knows what mysteries of therolinguistics we haven’t yet cracked. But animals can learn new vocabulary, like a dog learning Sit, and songbirds can combine their song elements in new and original ways, but no new meaning is created in the process. It seems very much that only humans can utter new sentences, and with them, we can imagine new ideas.
• Maybe an alien syntax is 3D in structure, spoken without reduction in dimensions at all. Maybe the medium isn’t sound or gesture but scent or something imperceptible to us. Maybe categories we think of as essential, like verb and noun, like speaker and word, are merely local conventions, hopelessly parochial even as we yearn to converse across the stars.
• Peterson makes his living inventing languages for TV and movies—for sci-fi, fantasy, and a surprising number of witches. I asked him which was the most alien alien language he’d invented, but he said, “Most of the time, those languages are not very alien. And they’re not very alien because the aliens themselves are not very alien.” Constrained by the realities of special-effects budgets and actors’ bodies, these aliens are, as far as language is concerned, pretty human. “They’re bipedal humanoids, they breed, they mate in the same way, they raise their young, they eat, they drink, they excrete, they live a fixed amount of time, they have a similar working memory.” Part of the rigor Peterson applies to his languages is that they suit the creatures who will speak it. And so if the aliens are not very alien, the language can’t be either. In those cases, he said, “It was more like creating a human language for a strange culture that doesn’t exist on our planet.”
• He points out, in his book, Impossible Languages, “If we were biologists, we would not hesitate to claim that there are impossible animals: an animal that produces more energy than it absorbs, for example, or an animal capable of indefinite growth. We could make such a claim because all organisms are constrained by physical laws, like entropy or gravity.” And so, could we not imagine a language that similarly violated whatever laws constrain language?
• Syntax allows us to create infinite meanings constrained by a finite word list—and linear word order. Time and the human vocal apparatus limit us to one word after another, but our brains somehow track the syntax humming beneath the surface. “Words,” Moro writes, “come in sequences: this is perhaps the only incontrovertible fact about human language.” But it is quite possibly a human limitation.
• In “Story of Your Life,” Louise recognizes that the heptapods have two distinct languages: she calls their spoken language Heptapod A and their writing system Heptapod B. Louise observes of the latter, “If I wasn’t trying to decipher it, the writing looked like fanciful praying mantids drawn in a cursive style, all clinging to each other to form an Escheresque lattice, each slightly different in its stance.” She calls the biggest sentences “sometimes eye-watering, sometimes hypnotic.” And, it turns out, becoming fluent in this nonlinear language gives her access to the heptapods’ nonlinear experience of time. In the movie adaptation, Heptapod B looks more like ink blots arrayed on a circle, trailing fronds like dye seeping through water. It’s beautiful but, David Peterson pointed out to me, not actually nonlinear: the line is just drawn in a circle. Peterson did introduce me to a visual language that’s truly nonlinear, called the Elephant’s Memory. Developed by author and designer Timothée Ingen-Housz beginning in 1993, the Elephant’s Memory consists of about a hundred and fifty logograms, pictures that stand in for elements of meaning, which are arrayed into sentences with rules that determine their form and placement. (Being nonlinear, sentences like I made the house burn and The house burned because of me are identical.)
• Nonlinearity is easy enough in writing, but the nature of time and vocal cords constrains our spoken speech to one word at a time. Systems like sign language do open up possibilities of simultaneity. In American Sign Language, for example, ideas are conveyed simultaneously with hand gestures, facial expression, and bodily cues, among other elements. And of course, we even layer meaning onto spoken language with inflection and body language. But for language itself, as Moro writes, “Words come in sequences.”
• But in the much likelier (still possibly very unlikely) case of an intercepted message, we would have no interaction, just static text. There are still dozens of Earth languages (or writing systems) that remain untranslated, human mysteries uncracked. A deliberate message might come with a primer—in Contact it uses basic arithmetic to teach logical relationships, which then allows symbols and words to be defined. But how can we hope to communicate across light-years if we can’t even understand ourselves across a few millennia on Earth?
• The extraterrestrial finding a Voyager, decoding its schematic, setting the record to play. And then she wonders: What could the sound essay mean to them? For decipherment purposes, the greetings in fifty-five languages are a nightmare—instead of a cleanly organized Rosetta stone, they’re a mishmash, all over the place, each speaker saying whatever they were moved to say. You can’t learn a thing about their meaning by putting them next to each other, and you’d give yourself a headache to try. The photographs, two-dimensional representations of a three-dimensional world, depend not just on humanlike visual systems but on human conventions that are as culturally anchored as they are biologically.
• However, it’s another scientific principle that is most often invoked when “Story of Your Life” is discussed (though Chiang doesn’t name it in the story or even the note in which he explains the inspiration above): the Sapir-Whorf hypothesis. Essentially, this is the idea that the structure of a language determines a native speaker’s thinking.

Consciousness and Intelligence

• What if? is not an unscientific question. It drives every hypothesis and prediction, every leap and act of synthesis that moves us from the unknown toward knowing. Scientists imagine things every day.
• He chops the roots to bits in a rage and feels foolish. They’re just plants. But he also knows that with Pax a billion years older than Earth, its plants have had a billion years extra to evolve past Earth’s plants as well. “We know what plants do,” one colonist says. “They grow. They’re useful or they’re not. And that’s all we need to know.” But Pax’s plants have wills of their own. The vines aren’t at war with the humans, but Octavo realizes they’re at war with one another, one stand feeding the colonists but another poisoning their rivals’ new pets. For a generation, the Pacifists fertilize the friendly vines in exchange for protection. It’s a simple system of mutual benefit. But then the humans find the rainbow bamboo. When a couple of humans camp near it one night, this bamboo sprouts a rainbow shoot in seeming greeting, and offers them delicious fruit they’ve never seen it produce before. But when they stop eating the fruit, the humans go through what feels for all the world like withdrawal, headachy and tired. Was the fruit a ploy for dependence, the bamboo’s attempt to keep the possibly helpful humans nearby? Or was it just a plant like any on Earth, no wilier than a tobacco leaf or coffee bean?
• A common way to try, to evaluate self-awareness, is the mirror self-recognition test. A spot of dye is put on an animal’s body in a place they can only see with a mirror. Shown themselves—and the spot—in a mirror, a self-aware animal will realize that the reflected body is theirs, and use the reflection to investigate the spot, or try to remove it. “It is generally accepted,” Rowlands writes, “that humans over the age of 18–24 months, common chimpanzees, bonobos, and orangutans consistently pass the test.” (Gorillas often fail, perhaps because they are so averse to looking one another in the face other than in aggression.) Claims have been made, too, for elephants, dolphins, pigeons, and manta rays. Even some fish, recently, which leaves many to question the usefulness of the test entirely—or our expectations for which animals might possess self-awareness. But we must be sure not to infer too much from the mirror test. It’s often cited as proof of self-awareness, of consciousness, of thought. But what it really measures is: Can a being recognize their physical self, and do they know that what they see in a mirror is a representation of their own body? Perhaps the fish aren’t doing anything so strange.
• In work published in 1960, Eiseley marveled that dolphins should have evolved to be so intelligent since they have no hands with which to make tools or interact delicately with their environment. “It is difficult for us to visualize another kind of lonely, almost disembodied intelligence floating in the wavering green fairyland of the sea—an intelligence possibly near or comparable to our own but without hands to build, to transmit knowledge by writing, or to alter by one hairsbreadth the planet’s surface.”
• “In the course of feeding Circe, if she left the area while I was still feeding her, I had to find some way of communicating you’ve done the wrong thing.” So Reiss essentially would give her a time-out. If Circe swam away, Reiss would walk away from the edge of the tank for a minute. Once Circe returned, so would Reiss. Eventually Circe learned. Then, one day, Reiss forgot to cut the fins off one of Circe’s mackerel tails. “It was my mistake. Circe looked up at me, her eyes were wide, she spit out the fish, and she made a beeline across the pool and took a vertical position and just stared at me. Was she giving me a time-out?” Reiss recognized that this anecdote was just that: an anecdote, not data. But a few days later, she—purposely, this time—gave Circe tail fins, and every time, Circe gave her a time-out. Reiss felt, then, that she wasn’t just studying the dolphins; she realized that they were trying to understand humans, too. That’s when she realized, “these are big, beautiful, intelligent animals, and we need to find new ways to study them.”
• “It’s kind of like if you asked, ‘Who’s more talented, Michael Jordan or Mozart?’” A dolphin can know you’re pregnant just by looking at you (or rather, echolocating into you), but if you put an object in a sound-opaque bucket and move the bucket, even if the dolphin watches you do it, they won’t know where the object has gone. It seems bafflingly obvious to us, and, indeed, Jaakkola and her team assumed dolphins would easily ace this object-permanence test when they ran it. But when we don’t center human abilities, there’s less to take for granted. “In their world,” Jaakkola said, “there aren’t a lot of things that go into containers that they move.” Tens of millions of years in the ocean will drive many kinds of intelligence, but tracking objects in buckets isn’t one of them. Who knows what other kinds of capacities they have that we can’t even imagine?
• Consciousness, then, is the ability to experience existence. It does not require intelligence, thought, or self-reflection, just the awareness of being.
• A bat’s presence is plenty alien, the frenetic flitting and chirps; what we know of their senses confirms it. “Bat sonar,” Nagel writes, “is not similar in its operation to any sense that we possess” and “there is no reason to suppose that it is subjectively like anything we can experience or imagine” (emphasis mine). It’s not just that bats perceive the world through a different sense; we cannot assume that their experience of a sonar world can be mapped at all onto our visual world. And that’s before even getting to the ways that living by sonar rather than sight would shape a consciousness beyond simple perception.
• As Louise learns the aliens’ language, she finds that their spoken and written languages are entirely distinct. And as she becomes proficient in the written version, even able to think in it, she finds her mind reshaping around the nonlinear language. It’s not only the alien language that is nonlinear, it turns out, but the aliens’ entire experience of reality. Louise tells us that it “introduced me to a simultaneous mode of consciousness.” She finds herself able to “remember” the future, now, as well as the past—including the daughter she will have with Gary, knowing full well that this daughter will die young. But Louise doesn’t feel herself stripped of free will; instead, she discovers “a sense of urgency, a sense of obligation to act precisely as she knew she would.” She recognizes that, even then, she is not experiencing reality as the aliens do—she is still human—but not as her brain was trained to, either.
• In the most basic sense, this is a question of hardware. Humanity has advanced so dramatically over the last hundred thousand years, but individual human beings are no more advanced than we were at the dawn of our species. Take a baby from the people who painted the Lascaux caves and raise them today, and they’ll be keeping up with their twenty-first-century friends. But smart machines, the thinking goes, can build ever-smarter offspring. As Shostak spitballed, “As soon as you have a computer that has the cognitive capability of a human...within 30 more years, you have a machine that has the cognitive capability of all humans put together.
• Dick thinks this happens because of what he calls the Intelligence principle. AI, genetic engineering, biotechnology—these are all ways to increase intelligence. “Given the opportunity to increase intelligence (and thereby knowledge)...any society would do so, or fail to do so at its own peril.” In other words, any society that doesn’t use any means possible to make its people more intelligent risks its own doom. “[C]ulture may have many driving forces,” Dick writes, “but none can be so fundamental, or so strong, as intelligence itself.”

Life's Origins and Definition

• The ancient ones hoped that their scattered children would, through the requisite cooperation, come together in harmony to hear their message. It’s a bit like finding out God exists. Or maybe it’s even more meaningful because your creator isn’t an all-powerful being but just someone like you, someone who came before and made you in their image, yes, but so that the universe might continue to be known and explored, so that life’s legacy might continue. And they not only made you but made the many species you’ve come to know across the galaxy. Not God’s children but kindred, nonetheless.
• While for centuries the existence of extraterrestrial life had rested on the assumption that where there was appropriate matter, life sprung into being, sparked by some “vital force,” Louis Pasteur disproved the theory with a few flasks of sterilized broth in 1859, and in the mid-twentieth century the origin of life was understood to be a momentous event of complicated and lucky chemistry.
• The same year that Darwin published On the Origin of Species, 1859, Louis Pasteur put spontaneous generation to bed. He was less trying to disprove it than prove the validity of germ theory (which holds that diseases are caused by microorganisms too small to be seen), but the two were intertwined. Pasteur showed that sterilized beef broth generated nothing spontaneously, in conditions where broth usually would. It wasn’t something about the broth that gave rise to life, it was something invisible living in it, something that could be boiled off and killed.
• Today, we know the building blocks Miller sought to synthesize are actually already abundant: interstellar dust is filthy with organic molecules, and meteorites crash to Earth laden with amino acids. But a shopping cart full of ingredients doesn’t make a cake. So some researchers today focus less on building blocks than processes, the reactions and pathways that use and produce the various molecules we know to be components of biochemistry.
• Steven Benner was a pioneer in the field of synthetic biology, one of the first researchers to create an artificial gene. Now, his lab studies the origin of life—specifically, the origin of RNA. These early complex molecules are his holy grail. “If you can get to RNA on an abiological process,” if you can make these molecules of life out of nonliving chemistry, “you’re almost home.”
• How might it have happened?” These researchers aren’t trying to prove how life started on Earth. They realize the futility of that question. Even with a perfectly complete chemical theory, replicated and proven in the lab, you could never confirm that it worked the same way on Earth those billions of years ago. The value is more in understanding the options and their implications. Could life arise like this? Not winnowing down the possibilities but manifesting them.
• The synthetic bacterium Synthia, built by researchers at the J. Craig Venter Institute, whose genome was assembled and sequenced piece by piece. And still, there were mysteries. “Even though they know every single gene in that system,” she told me, “they still don’t know what about sixty of those genes do.”
• Carl Sagan wrote a survey of the possible kinds of definitions of life—physiological, metabolic, biochemical, genetic, and thermodynamic—and showed how there are exceptions to all, entities that meet the criteria but are clearly, to us, not alive, or vice versa. “An automobile, for example, can be said to eat, metabolize, excrete, breathe, move, and be responsive to external stimuli.” It seems almost more alive than a dormant seed or spore. Except we know that it’s not. But the problem may not be finding the right definition. Philosopher Carol Cleland said that even attempting to define life shows that we’re on the wrong track. She told Astrobiology Magazine, “Definitions tell us about the meanings of words in our language, as opposed to telling us about the nature of the world.”
• Walker thinks that our understanding of life, as a phenomenon, is right now where we were with gravity before Newton. We can describe what we see, but we have no sense of the underlying principles—we just see an apple falling to the ground. She thinks that without a theory, a deeper understanding of what life is, the search for it beyond Earth is preemptively doomed. And if we don’t understand the phenomenon of life, how could we begin to mark its origin?
• To Walker and Adamala, a biomarker is anything that could only be made by life’s corralling of information. Walker picked up a glass mug on her desk. “Something like a cup doesn’t appear in the universe without a living process.”
• Life, to Cronin, isn’t a sum of organisms, it’s the inevitable result of the laws of the universe. “I think the process that drives the formation of life,” he told me, “is as abundant as gravity is in the universe.” Not every object exerts the same gravitational force—the sun is more massive than a pencil, so the sun seems to have abundant gravity while, to our experience, the pencil has none—but gravity is still inherent in all matter. It could be the same, Cronin says, for life. “I think evolution is an intrinsic feature of the universe, like gravity. It’s just biology speeds it up.”
• Mike Russell, who first imagined life emerging in the microscopic pores of a system of undersea vents, also sees life’s origin as just part of the universe’s unfolding. In an article about Russell in Aeon, Tim Requarth wrote, “If you think of life in terms of energy, then life’s emergence connects back to the very source of energy flow, the Big Bang itself.” Energy and matter didn’t dissipate after the Big Bang, didn’t flatten out like a puddle into homogenous atomic soup, but clumped and hiccupped into structure. Stars formed, and planets, and surfaces, and seas. That disequilibrium eventually led to us as well. From this vantage, the question of whether we’re alone could almost become moot. We’re not alone because we’re not separate from the swirl of a galaxy’s arms or the way wind catches dust in a gyre. We’re no more an anomaly than an atom is. How could we ever consider ourselves alone?
• We can’t define life. And we can’t define intelligence, right? We can simply, in our case, look for evidence that something has modified its environment, in ways that we can sense remotely over vast distances.
• what seems like one very unlikely event on the ancient Earth: the time one single-celled organism sucked up another and thus entered into a symbiotic relationship that would eventually give rise to all complex cells. All multicellular life—and plenty of single-celled life, too, like amoebae and paramecia—has cells full of complex structures. Their genes are cloistered in a nucleus, and they have a host of internal organelles, the litany of whose names may flash you back to high-school biology: ribosomes, lysosomes, Golgi apparatus, endoplasmic reticulum (that last a beautiful set of words to rival cellar door). Ribosomes translate genes to proteins, lysosomes sequester enzymes from the rest of the cell, the Golgi apparatus packages proteins to shuttle them off to their destinations, and the endoplasmic reticulum folds and transports protein, among several functions.
• Those mitochondrial genomes that tell us about these organelles’ independent origins also tell us that the origin was shared, pointing back to a common ancestor. Just one. A single archaeon engulfed one bacterium, and their marriage (or something even more intimate) led to all the life you can see with your naked eye and plenty of smaller life besides.
• Yet the next phase of my research—working weirdly backward—was on the study of the origin of life. I talked to Lane and Martin as well as Sarah Walker and Lee Cronin and several other researchers digging into the questions of life’s origin and life’s essence—what is it that changes in matter when it becomes alive? Boundaries between this world and others began to fade. It wasn’t life elsewhere that held the magic, anymore. It was that life existed anywhere, at all. We were just as improbable, and as important, as whatever we hoped might exist on worlds beyond.
• Historically: life arose on Earth just about as soon as it was able to, but Earth is not the oldest planet in the galaxy, nor is the sun in the oldest generation of stars. So older stars with planets similar to Earth would have gotten a few billion years of a head start. Probabilistically: humanity is a relatively new entrant to the ranks of technological civilizations.

Human Assumptions and Biases

• The most famous way of thinking about the odds of alien life is the Drake Equation. Except, in practice, it hardly works as an equation at all, and it provides no definite answers. Social scientist and NASA consultant Linda Billings more accurately calls it the “Drake Heuristic,” an approximation that reveals as much about the analyst’s assumptions as it does about the question being asked.
• Our visions of space are a reflection of our selves and of our humanity—like the building blocks of a telescope, a mirror and a lens.
• Most of the star systems we’ve found look nothing like ours. Partly, that’s due to the methods we’ve had for detection. The Kepler space telescope, which searched for exoplanets (via the light curve/transit method) from 2009 to 2018 and is responsible for roughly half of the planets currently known, was most sensitive to large planets with tighter orbits around smaller stars. But it does seem like our solar system may be strange. In line with the Copernican principle, the base assumption before we’d found any exoplanets was that our solar system would turn out to be average. But when scientists started finding exoplanets, their elegant model was shown to be far too clean. That first planet found around a sunlike star, 51 Pegasi b, is 150 times more massive than the Earth—about half the mass of Jupiter—but it orbits closer to its star than Mercury orbits the sun. More of these hot Jupiters were found soon after. They’re not particularly common, it turns out—they account for maybe 1 percent of planets—but being huge and having very short orbits, they were the easiest and fastest to find.
• We don’t see Earth as a planet, after all, in daily life. It took math and insight for ancient thinkers to realize the Earth was a sphere and not a flat surface; it took Copernicus’s intuition and Galileo’s telescopes to realize that the planets and Earth alike were spheres, all in their parallel orbits. To study planets is to see Earth as one of many, among comrades in the solar system and kin in the cosmos, just one of what turn out to be bountiful worlds.
• Ellison’s job, then, is to be aware of “all the subtle subconscious things that make up something that we believe is natural.”
• Humans are considered the most advanced life-form on the planet, having a more perfect form than the other animals and possessed of unique qualities.” In astrobiology, she cautions, this narrows our imaginings because we incorrectly think we have just one example on Earth of intelligent life.
• When writer Charles Foster set out to understand a set of animals—badger, otter, fox, deer, and swift—he did so by living like them, and among them, for weeks at a time. As he writes in his book, Being a Beast, he finds himself tuning into his senses, like smell, in new ways and discovers a powerful connection to his animal compatriots. But, Nagel might point out, Foster learns what it is like for a human to be like a badger; we still cannot know what it’s like for a badger to be a badger. “If I try to imagine this”—Nagel refers here to a bat being a bat, but it easily applies to badger (and alien)—“I am restricted to the resources of my own mind.” He argues that whatever we imagine is an alteration to human consciousness; it is impossible, he says, to imagine batness qua bat.
• Our contemporary understanding of color is primarily defined by hue—the position on the rainbow spectrum—with variations in lightness, or value. (Red and pink have the same hue, but pink has a lighter value.) There’s also saturation, the intensity of the color—vivid blue versus the less saturated gray-blue. Sassi sees in Greek descriptions of color more emphasis placed on saliency, which is how much a color grabs your attention. Red is more salient than blue or green, and sure enough, Sassi finds that descriptions of green and blue in Greek are more focused on the qualities that grab your attention than on the rather unsalient hues. She writes, “In some contexts the Greek adjective chloros should be translated as ‘fresh’ instead of ‘green,’ or leukos as ‘shining’ rather than ‘white.’” It wasn’t that the Greeks couldn’t see blue, they just didn’t care about blueness as much as other qualities of what they were seeing.
• A truly alien alien, likely as their existence may be, is so incomprehensible that stories about them just become stories about human beings.
• So many stories of first contact, written by white American or European authors, replay the horrors of colonization by putting America or Europe into the position of subjugation by colonizing aliens, karmic comeuppance for our culture’s past sins, imagining that the worst horror would be to be subjected to the atrocities to which we once subjected other humans.
• What is here is dangerous and repulsive to us. This message is a warning about danger, as well as This place is not a place of honor...no highly esteemed deed is commemorated here...nothing valued is here.
• We are only seeking Man. We have no need of other worlds. We need mirrors. We don’t know what to do with other worlds. A single world, our own, suffices us; but we can’t accept it for what it is. We are searching for an ideal image of our own world: we go in quest of a planet, of a civilization superior to our own but developed on the basis of a prototype of our primeval past.
• All of these scales of progress are built on human assumptions, specifically the colonizing, dominating, fossil-fuel-burning history of Europe and the United States.
• Stapledon believed he was living through a turning point on Earth. We often feel the same today. But isn’t there something self-centered about that? It seems in stark violation of the Copernican principle—the idea that humans are not privileged observers of the cosmos, that the Earth is not the literal center of the solar system, and humanity is not the metaphorical center of the world. If there’s nothing special about us, then why should there be anything special about the moment you and I and Olaf Stapledon happened to be born into?
• Drawing from Earthly examples, we face a seductive trap of the Copernican principle. We see technological culture as dominant on Earth, and so we project that out into the cosmos. Perhaps it’s another way to seek kinship, to believe we’re not alone. Perhaps it’s an easing of guilt or, as Frank frames it, a path past self-flagellation to action. But it’s also simply not the entirety of culture on Earth, as Denning writes. “Indeed, gathering-hunting life-ways with quite minimal technology worked very well under some circumstances, and persisted in many parts of the world until very recently, until these communities were forced by political circumstances to change.” Looking at all human cultures, not just the loudest ones, there’s no universal trend toward technological advancement at all.
• My mom used to tell me, “You can’t imagine what love is until you have a child,” and I always thought she meant more love (and was perhaps one chardonnay too deep). I didn’t realize until I had my own son that she wasn’t talking about quantity but about how love becomes something utterly different, a singularity of sureness of feeling. There’s what we can imagine, and then there’s what we can know.

Technological Advancement and Civilization

• Their relationship is mutually beneficial. The Pacifists provide Stevland with water and fertilizer; he gives them fruit produced with biochemical virtuosity, customized with stimulants, painkillers, or drugs.
• stories about technology and power and politics and how civilizations meet, and what happens next, require our critical attention instead of our unthinking allegiance.
• Cosmologist John D. Barrow proposed microscopic manipulation, going from Type I–minus, where people can manipulate objects of their own scale, down through the parts of living things, molecules, atoms, atomic nuclei, subatomic particles, to the very fabric of space and time. Frank proposed looking not at energy consumption but transformation, noting that a sophisticated civilization does more than bring a planet to heel, it must learn to find balance between resource use and long-term survival.
• When Stapledon writes, “We were inclined to think of the psychological crisis of the waking worlds as being the difficult passage from adolescence to maturity,” he presaged one of Carl Sagan’s more famous ideas (or sound bites): that we are living through humanity’s “technological adolescence,” in possession of new power but not yet possessed of the maturity to wield that power well.

Future and Post-Human Possibilities

• We’re also, on some level, seeking new homes for humanity, the search for our future among the stars. But even if our descendants never leave Earth, a cosmos full of Earthlike worlds is one that is, wholly, our home.
• The new age of human evolution which the Oankali would begin is, much like our own age, not driven by natural selection but by deliberate choices. (Perhaps their approach isn’t so alien after all.) For some intelligent life, those choices could include technology—cyborg life and AI, as we’ll see in the next chapter—but for the Oankali, genetic manipulation is not distinct from nature. In fact, all of their technology, including their starfaring ship, is alive, engineered and grown from natural forms.
• If we’re children, then our mistakes are just the messy path of learning; if we’re children, the grown-ups can still come and help. We don’t want this violent, greedy, suffering version of humanity to be our final form. Transcendent outsiders give us hope and, hopefully, guidance. But even just knowing they are out there—and that they are reaching toward us—could be enough to change the world.
• It’s a matter of entropy, in a way, information subject as anything else is to the second law of thermodynamics—not decaying out of order but morphing and shifting, small changes adding up over the centuries until you’re somewhere entirely new. And that’s with a relatively contiguous culture. Imagine a disaster, or a social break: humanity survives, perhaps fully rebuilds, and encounters a mystery in the desert. You need these future humans to not only understand the warning but also believe it. All the promised curses in the world didn’t stop nineteenth-century archaeologists from broaching the sealed doors of the pharaohs’ graves, after all.
• It’s all wishful thinking—that aliens find the probe, that humanity lasts another 10,000 years. But for now, these messages offer us a chance to project a hopeful, idealized version of humanity. Welcoming, laughing, suffused with love—looking forward, looking outward, and not alone.
• Lem is also right that our narrative quests are often for a superior civilization. When we imagine aliens, we’re quite often imagining versions of our future selves, a superior civilization evolved from a common or analogous primeval past. We look to the stars, to the future, and hope or wonder: That could be us, too.
• He thinks a Dyson sphere or swarm could accumulate in a similar manner. “If the energy is out there to take and it’s just gonna fly away to space anyway, then why wouldn’t someone take it?” Wright knows the objections: that this imagines a capitalist orientation, a drive to “dominate nature” that is by no means universal, not even among human societies.
• Seth Shostak, senior astronomer at the SETI Institute, told me that he thinks imagining that intelligent aliens would be like us is wrong in two ways. First, it’s self-centered, and second, “I think that really misses the point, mainly because, if you think about it, the most important thing we’re doing in this century is inventing our successors.” He thinks that most of the intelligence in the universe, abundant as it may be, is likely synthetic. “If you’re going to say the aliens are what we will become, then the aliens are machines.”
• In a 1981 interview, Kardashev himself said that he thought humanity might transition to electronic, or silicon, life a hundred years in the future. And every so often, he thought, we would trade in our bodies for a new model. “It seems that electronic life is better.”
• Vinge sees ways the technological singularity could go well or not so well for humans, but he considers it inevitable. So does Seth Shostak. If you build machines and make them smart, eventually you’ll make them smarter than you.
• Vinge imagines four possibilities that could bring us to that point (individually or in concert): superhumanly intelligent computers; large computer networks that along with their human users attain a collective superhuman intelligence; computer/human interfaces that through their intimacy attain superhuman intelligence; artificial augmentation of human biology, such that the superhuman powers are still, in their way, within us. As for the outcomes of these developments, Vinge writes, “[F]or all my technological optimism, I think I’d be more comfortable if I were regarding these transcendental events from one thousand years’ remove...instead of twenty.” He sees the extinction of the human race as one possible, literal feature of the “Posthuman era,” or perhaps we’ll simply be subjugated or ignored. But good or bad, Vinge thinks the singularity is inevitable. No guardrails or precautions can hem it in. No governmental regulations could divert the quest for the advantages advanced AI could offer, a more mercenary version of Dick’s Intelligence principle. “If the technological Singularity can happen,” Vinge writes, “it will.”
• The Beyond is full of civilizations comprising countless flesh-and-blood (or whatever they’re made of) alien species. Powers are essentially super-advanced AI, so far beyond mortal comprehension that they’re something like gods—though they are real and do sometimes intervene in galactic events.
• If aliens are millennia older than us, they may already be living our futures. And for all the ways aliens could be “advanced,” we focus on technology because that’s how we could find them.
• Theory says should; imagination says might.