Alien Nations: Why Life on Other Planets Will Resemble Ours

[Pages:9]Alien Nations: Why Life on Other Planets Will Resemble Ours

Hard science offers a remarkably detailed portrait of how extraterrestrials may live -- and clues on where our own civilization is headed

Steve LeVine, January 28, 2020

Scientists, now routinely detecting potentially habitable planets in space, are the closest yet to determining the truth about aliens. But there is another question that almost none talk about: If other beings do populate the universe, what are they doing out there?

Are the possible inhabitants of Teegarden b, some 12 light-years from Earth's solar system, driven to explore and migrate? Do they have a great power rivalry with the citizens of Teegarden c? What about the potential folks on the "super Earth" exoplanet K2?72 e? Are they inclined to hate and love according to tribe?

Such questions may appear to be only the stuff of science fiction. But it turns out that the hard laws of physics, biology, and geophysics apply on other habitable planets just as they do on Earth. And they suggest a remarkable level of detail about how alien societies might operate, says the astrophysicist Frank Drake, detail that among other things could help resolve some of humankind's most charged debates, from how to confront a changing climate to how to treat beings from other places.

Drake is the man behind the Drake equation, the intellectual foundation of the six-decade-old effort to find technologically advanced alien life. At 89, he is still one of the most respected figures in space science. The search for aliens has turned up nothing thus far, but Drake says he has at least some idea of what space societies will look like. "In many, many places, evolution would produce intelligent species capable of making things," he said, sitting in front of a mug of coffee in his California home, up the road from the beach amid millennium-old redwoods near Santa Cruz. "They will make technology we could detect from a great distance. That will be a common event. They will first make [primitive machines] and eventually radar transmitters, and once they make a radar transmitter, we can discover them." Drake barely blinked. Science cannot tell you the precise social details of an alien society -- is there democracy? Do otherworldly beings go through courtship? But the principles governing atoms, chemistry, and fundamental forces everywhere can be used to infer its broad shape. If there are technological societies in space, for instance, the extraterrestrial population almost certainly lives in cities and uses language, since such cooperation underpins civilizations. Given that legislatures, iPhones, and Simone Bileses do not arrive from nowhere, its population is the beneficiary of competition and cooperation. There would have to be politics and war, since that is how disputes are resolved. There would be a locus of power in the form of leadership. That leader -- a monarch, a parliament, a president, whatever -- would be tribal and territorial, since a society is a coherent group with boundaries, even if there are divisions within it, according to Nicholas Wright, a neuroscientist at University College London.

Hence Drake's eponymous equation, the more or less standard formula for estimating the number of technological space civilizations, and his lifelong search for the radio or light signals that he is certain aliens are transmitting, as if shouting to Earth, "We are here."

The Drake equation consists of seven variables involving the state of the universe that, when multiplied, assume the answer to one of the universe's great mysteries: Are we alone? We are not, Drake responds, and with his equation goes on to attempt to calculate just how many technological societies are out there. In 1950, that question was the subject of one of the most consequential lunches in the history of space science. The Nobel Prize-winning physicist Enrico Fermi was dining with other science luminaries at Los Alamos, the national laboratory in New Mexico where the atomic bomb was invented, when he uttered three words that have haunted alien hunters ever since: "Where is everybody?" That is, if there are so many technologically able extraterrestrials, as many scientists thought even before Drake, why had no one yet seen one? The question became known as Fermi's paradox. When Drake proposed his equation in 1961, he was not responding directly to Fermi's question -- Drake's calculation tells nothing about the location of aliens. Instead, Drake, then a young astronomer at Green Bank

Observatory in West Virginia, was trying to devise an organizing principle for a meeting of scientists that he had been asked to host. On the agenda was determining a strategy to detect signals of alien life using a radio telescope, and so Drake -- figuring that for starters the scientists needed to grasp the sheer difficulty of their task, meaning the number of space civilizations that might exist -- formulated what would thereafter be called the Drake equation.

Despite the exoplanet revolution, there has been no conclusive sign of alien life, which means Fermi's question persists: "Where is everybody?"

The meeting quickly became space lore, and launched a formal alien hunting initiative called the Search for Extraterrestrial Intelligence, or SETI for short. The meeting's attendees would dub themselves the "Order of the Dolphin," after discussions they held about communication among species here on Earth, and NASA would spend about $78 million on the quest over the subsequent years. Drake himself became among the field's biggest celebrities. From the appearance of bacteria to intelligent humans discovering fire and electricity, a compact synthesis of science and history on Earth told him that alien voices could be found if we just listened hard and long enough. "To me, it seemed that a particular course of growth should happen often out there," Drake said. "There should be something there to find. That's the whole story in a nutshell." As straightforward as the equation seems written in full, it turned out that neither Drake nor the rest of the SETI field could assign a confident numerical value to any but the very first of the variables -- the rate of star creation. They could not even be sure how many stars hosted planets, another key Drake variable. For more than three decades afterward, no one got any further. Federal funding for SETI research dried up, cut off by Washington politicians who said it was a waste of money. But in 1995, a Swiss astronomy PhD candidate named Didier Queloz, working with his professor, Michel Mayor, at the Haute-Provence Observatory in southern France, made a blockbuster discovery. Monitoring the light from a star called 51 Pegasi, 50 light-years from Earth, Queloz detected a wobble that suggested the presence of a nearby, smaller body, such as a planet. For six months, they checked and rechecked their observations, then made an announcement: They had found the first clear evidence of a planet orbiting a sunlike star outside the solar system -- what's known as an "exoplanet." It marked the start of a scientific revolution -- the first actual proof that there were in fact places where aliens might live. Last year, Queloz and Mayor shared the Nobel Prize in physics for their work.

Ever since, astronomers scanning the skies for more exoplanets have been filling in the Drake variables. They have concluded, for instance, that most stars have orbiting planets and that a fifth of them are in principle habitable, meaning that, among other attributes, they can sustain copious liquid water, an atmosphere, and plate tectonics. More and more evidence suggested that there was plenty of space for alien life and civilizations to arise.

But despite the exoplanet revolution, there has been no conclusive sign of alien life, which means Fermi's question persists: "Where is everybody?" In a 2016 paper, the astrophysicists Adam Frank of University of Rochester and Walter Sullivan of the University of Washington took on the most elusive of the Drake unknowns of all: How long do space civilizations, including our own, generally last? Only by calculating this number could the field know if advanced alien societies endure long enough to still be around for us to find them -- whether, for instance, they might have once existed but have since gone extinct, which might perhaps explain why we apparently have yet to be contacted. Short of conducting a census of the galaxy, there seemed no way to find the variable. But Frank and Sullivan jury-rigged the equation, swapping in a new and bigger question: Are humans the only technological civilization that has ever existed in space? It was another way of solving the Fermi paradox, and, they argued, the final Drake variable. Their answer was that we are almost certainly not the sole advanced space civilization ever. The odds for what is known as the "rare Earth hypothesis" are smaller than one in 10 billion trillion, or "about as likely that you'd be hit by lightning four times in one year," the pair wrote. Technological species have "probably happened many times before." We just needed to keep looking. Which is why one might ask not where is everybody, but rather, what are they all doing?

Around the world, scientists have been exceedingly eager to continue the search for potentially habitable exoplanets, which have reached 55 and counting, triggering great drama while they have done so.

But aside from some outliers, scientists have seemed mostly disinterested in detecting and communicating with the actual aliens who might live among the stars. They have fashioned themselves as hunters of exoplanets, not of the beings who might live there.

Last year, the theoretical physicist Avi Loeb suffered a public beating by peers for suggesting that 'Oumuamua, the first object from another solar system to be spotted flying through our sun's stretch of the galaxy, could be of extraterrestrial origin. Loeb is no fringe conspiracy theorist -- he's the chair of Harvard's astronomy department -- but colleagues still branded him a sensationalist who had committed an "insult [to] honest scientific inquiry to even suggest it," as the astrophysicist Paul Sutter put it.

In a May interview with the geopolitical analyst Ian Bremmer, Loeb pushed back. Intelligent alien life has existed, he maintained. The only question was timing -- as Frank and Sullivan had suggested in their paper, technological races like Homo sapiens could be prone to self-destruction, in which case they might appear and vanish relatively quickly, a blip on a galactic timescale measured in the billions of years. Humans, after all, have only been a technological civilization for little more than a century, and we have already developed nuclear weapons that might destroy us, not to mention a fossil fuel-driven economy that is triggering devastating extreme weather events, with more challenges -- advanced A.I., gene-edited weapons -- coming soon. 'Oumuamua -- a dark red object smaller than 1,000 meters in length -- might be debris from a space civilization that had driven itself to extinction. Loeb held his ground, but still appeared to convince few of his critics.

Why does the space community seem so hostile toward the subject of alien life? "This is still a very puzzling question to me as well," Loeb said in an email exchange. "Given that we exist, it is very natural to argue that similar outcomes will result from similar circumstances." One reason, he reckoned, is that the subject of extraterrestrials can be generally fraught, often veering into outright science fiction. Double-digit proportions of Americans believe that aliens live among us, much as depicted in the film Men in Black, and suspect that the government is hiding what it knows about extraterrestrials. Astronomers want to steer clear of such speculation, Loeb said.

In a poll conducted for this article, Ipsos found that 57% of Americans think there are extraterrestrial civilizations, though just 26% expect them to be like the Earth's. So do many other people. In October, a gathering was held outside Frankfurt, Germany, for the citizens of

"Asgardia," a group of people who, when the technologies are ready, say they intend to boost themselves into the cosmos and live there permanently as the first "space nation." One would feel certain that here was a place to find vibrant discussions of alien societies. One would be wrong. Asgardia's "head of nation," an Azerbaijan-born Russian billionaire named Igor Ashurbeyli, who runs a weapons contracting conglomerate, says he himself does not believe there are aliens. "There are two opinions," Ashurbeyli explained. "One says there are aliens, and the other says they don't exist. Neither has any evidence. I just picked the one I like best. It would be a pleasure to be proved wrong."

That was the sensibility running through the event. The subject of space geopolitics did not seem even to arise. It turns out that Ashurbeyli is not unusual among space billionaires, either. SpaceX CEO Elon Musk, who is racing to establish human settlements on Mars, told a Texas group around the same time, "People often ask me, `What do you know about the aliens?' and I'm like, `Man, I tell you, pretty sure I'd know if there were aliens. I've not seen any sign of aliens.'"

Exceptionally smart and even visionary people seemed to think alien skepticism was savvy. But were they instead being unthinkingly rejectionist? The general American population strikes a different balance. In a poll conducted for OneZero, Ipsos found that 57% of Americans think there are extraterrestrial civilizations, though just 26% expect them to be like the Earth's.

Why does it matter? For his part, Loeb saw several advantages for humans in coming to understand what he called "alien sociology." If humans were to establish communications with several alien societies at once, for instance, "an interesting question to ask is whether the most abundant, long-lived civilizations are those who develop advanced technologies or those who live primitive lives like animals. Henry Thoreau would argue, based on his book Walden, that living close to nature has major advantages compared to industrial life. It is possible that we would have been better off by not creating advanced technologies that could kill us."

And say that we do discover that the worst is true -- that technologically advanced alien societies once existed but are now dead. That, as humans appear to be in the process of doing, they committed mass suicide. "We could still search for their relics, like surfaces of planets that were burnt up in a nuclear war, atmospheres that are polluted by industrial, not natural, molecules like [chlorofluorocarbons], planets covered by photovoltaic cells or lit by artificial lights," Loeb said. If we could unravel what killed them, we might avoid the same fate. Frank, the University of Rochester professor, calls these "the laws of planets," and advocates understanding and following them to save the Earth.

On Earth, urbanists and policymakers use fact-driven thought experiments to devise solutions to crises over the fraying social fabric as millions and millions more of us crowd into cities, and politics, economics, communications, and the climate become unrecognizable. Grasping the probable contours of civilization elsewhere could only make it easier to find solutions to our confounding state of affairs. "It is extremely important to understand what universal laws are at work and their boundaries in order to understand the future of socioeconomic beings on the planet," said Geoffrey West, a physicist with the Santa Fe Institute and author of the 2017 book Scale: The Universal Laws of Life, Death and Growth in Organisms, Cities and Companies. "By getting a different understanding, you can mathematize it, make it predictable, and know where it breaks down. If we had a different planet, what would happen?"

Frank Drake's assumptions notwithstanding, there is very little assurance that anyone will see or speak with an alien anytime soon. The main reason is that the Milky Way galaxy is so vast -- 100,000 light-years across, with 400 billion stars, 80 billion of them orbited by possibly habitable planets. Outside the galaxy, the observable universe as a whole holds an estimated 10 billion trillion planets. That is a ton of possible aliens, but spread over a ton of distance. Earth's radio transmissions, traveling at the speed of light but begun just decades ago, have reached only a fraction of that space as yet, and the same would hold for any alien civilizations broadcasting their radio waves toward us. Even if Drake or another alien hunter were to receive a radio signal today from Ross 128 b, one of the nearest habitable exoplanets, their response would take 11 years to get there, not to mention another 11 for the Rossian reply to reach Earth. Another possible answer to the cosmic silence is that space civilizations are deliberately laying low, surmising that humans may not be quite prepared to calmly welcome an alien life form.

Given those distances, astronomers say their search of the cosmos to date has been meager. Jill Tarter, a SETI pioneer, has compared the progress with looking for evidence of fish in the oceans by sampling only a single glass of water. Jason Wright, an astrophysicist at Penn State University and part of the school's Center for Exoplanets and Habitable Worlds, calculated in a 2018 paper that the actual volume searched is equivalent to a hot tub of water. Whatever the case, astronomers have barely looked.

Yet if your interests extend beyond identifying exoplanets or exchanging pleasantries from afar -- if you wish to explore the social and geopolitical behavior we may see should we encounter technological aliens -- your odds of success may be better than they might seem at first.

For starters, many of the rules of the cosmos are presumed to be universal: Beings on other planets would be subject to the same laws of motion, thermodynamics, entropy, gravity, and relativity as humans are. The same goes with chemistry and biology -- every planet is governed by the periodic table of elements and, if there is life, by the forces of natural selection. If a technological race has arisen, evolution has been the instrument -- organisms have engaged in fierce competition as well as cooperation both to become the beings they are, and to develop the technology they possess.

Any planet hosting intelligent life as we know it is likely to possess plate tectonics, the capricious machinery beneath our feet that makes the planet livable and at times hellish.

Many scientists and scholars are unconvinced that clues on Earth can be translated into how events will unfold in circumstances elsewhere in the galaxy. Brian Fagan, an anthropologist at the University of California, Santa Barbara, and an expert on the confluence of earth science and human history, is among the skeptics. "I doubt if there is any human experience on this planet that would have any resemblance to those on others, given their enormous variability in planetary and other environments," Fagan said. "In fact, I think it's impossible to predict them. Any history there would have a different shape, I suspect."

But a number of other experts say the hard sciences create a universal framework in which any civilization must grow up. Most relevant for alien hunters, scientists say that any planet hosting intelligent life

as we know it is likely to possess a feature of Earth's that is as important as it is underappreciated: plate tectonics, the capricious machinery beneath our feet that makes the planet livable and at times hellish. The earliest life on the planet -- in hot water vents at the bottom of the oceans -- thrived because of tectonics. So does the most complex life on Earth: us. When it comes to history-defining events, there may be no more important single driver than tectonics, the force that generally stirs things up, compelling life over Earth's 4.5 billion years to adapt, evolve, and continuously rejuvenate, all under the threat of extinction.

Because of tectonics, the Santorini volcano destroyed the Minoan civilization of the Aegean islands in 2000 B.C., and a series of sixth-century A.D. eruptions either in Iceland or present-day El Salvador are blamed for a 3.6 degree Fahrenheit drop in global temperatures that killed tens of thousands of Mayans, setting off a forced migration of people farther north in Central America, and half a world away hastened the collapse of the eastern Roman Empire. A 1755 earthquake and tsunami almost leveled the Portuguese city of Lisbon, but also ignited the work of the era's great philosophers, like Immanuel Kant and Jean Jacques Rousseau. Voltaire immortalized the catastrophe in his masterwork Candide. "Without the quake, we probably wouldn't have the Enlightenment," said Paul Saffo, a futurist at Stanford University. "The church lost its authority and philosophers were able to scoot out and do their thing."

The history and geopolitics on any planet with technological aliens will be shaped by these same forces, since intelligent life as we know it will require plate tectonics. Volcanoes, earthquakes, and tsunamis will destroy their cities and whole civilizations, and will at turns empower other population centers, drive mass migrations, and create the same kind of political frictions we have seen on Earth when people of different places collide.

That all of these events occur on dry land should not be overlooked. For 3 billion of Earth's years, complex life evolved in shallow seas, but a technological species only arose once life had spread to land. "No aquatic creature discovered fire, a radio transmitter, or electricity," Drake said. Tectonics made that transition possible, pushing continents above the oceans, crunching them together to create mountains, and pulling other land apart.

Technological alien life is also likely to be on dry land. When life climbed onto the land and eventually produced hominids, they evolved modern hands as necessities for grasping, throwing, and climbing in the forest, Robert J. Stern, a professor of geosciences at the University of Texas, Dallas, wrote in a 2015 paper. At night, the starlit sky ignited wonder, stimulated abstract thought, and helped lead to religion and then science. Much of human history -- perhaps all of it -- has been possible because of the action of tectonics.

"Plausibly," as Stern wrote in the paper, "a similar scenario can be imagined on other exoplanets."

Over the last century, the Earth has lit up. In nearly every corner of the planet, humans have built factories and paved roads, and on those roads put 1 billion vehicles. Since the start of the Industrial Revolution, energy consumption in England and Wales, the birthplace of coal-driven steam, has increased around 32 times, driving a 12-fold explosion in real living standards.

The unlocking of fossil fuels driving all this consumption has utterly remade life on Earth -- and transformed how fortune and political power are conferred. In just a couple of centuries, fossil fuels like coal and oil singularly catapulted humans from an agrarian species of perhaps 1 billion people into a technological civilization headed toward 8 billion. The sprawling fossil fuel industry became a geopolitical force all its own, turning companies like ExxonMobil into the equivalent of state actors and petrostates like Saudi Arabia -- a desert country with few resources save abundant crude -- into among the richest and most consequential players on the planet. Energy made intelligent society as we know it go.

Alien hunters think the same general pattern will apply elsewhere: Life and power will pivot on the development and possession of energy sources, and possibly reach a scale that John D. Rockefeller never imagined. In a seminal paper in 1964, a Soviet astrophysicist named Nikolai Kardashev proposed a standard ranking of technological civilizations in space. His yardstick: a society's ability to marshal energy. Quickly, the Kardashev scale took its place next to the Drake equation as a bedrock tool of alien hunting.

According to the Kardashev scale, Earth is a Type I civilization, one of possibly many space societies fueling their activities by maximizing the energy resources available on their planet, such as oil, solar, wind,

and geothermal power. Kardashev called such planets Type I because they are at the bottom of the civilizational scale, their ambitions constrained by the energy supplies from which they can draw. Our planet may be lit, but when you count everything, humans still harvest just a million-billionth of the total energy reaching the Earth from the sun, according to the physicist Michio Kaku. That includes fossil fuels like coal, which are the remains of prehistoric vegetation that was fueled, like everything else on the Earth, by the sun.

If humans ever do develop into a Type II civilization, which at the current rate of growth Kaku reckons could take another few thousand years, they will be capturing the sun's energy right at the source, not filtered by distance, Earth's atmosphere, or through the slow making of fossil fuels. Rather, humans would harvest the sun's entire 384.6 yottawatts, or 25,640,000,000,000 times humanity's power consumption of 15 terawatts in 2008. Such a massive increase in energy availability may give humans the resources to counter many of the natural existential threats that might arise, such as errant comets and recurring ice ages and other climate catastrophes, since our ability to deflect objects and adapt to geologic and cosmic forces will be vastly greater. Humans could even be able to shift the course of an earthquake.

But it would involve a gargantuan undertaking. The scale is suggested in a 1960 paper by the venerable theoretical physicist Freeman Dyson, who said that any alien species surviving a few thousand years after industrializing would be forced by the pressures of population and resource scarcity to figure out how to capture all the energies of its star. So if humans want to find aliens, we should search for a structure monumental enough to do just that. Dyson proposed one format: a shell surrounding a star and encompassing the orbit of the alien planet. Such a star would obviously be dark, with all its light staying inside the shell, but Dyson said it could be detected by searching for its radiation marks, what he called "infrared stars." A helpful researcher proposed that a "Dyson Sphere," as the structure came to be named -- though not by Dyson himself -- could be built by crushing up Mercury, Venus, and perhaps other planets as construction materials. The idea actually came from Dyson, who proposed that it would be possible to crush up Jupiter. It is difficult to fathom the type of geopolitical mind that would decide to pulverize a planet for bricks and mortar. Would you have to be megalomaniacal? Utterly reptilian? The same questions apply to the ambitions required to ascend to a Type III civilization, which describes a planet that is somehow harvesting the energy of its entire galaxy. One could imagine that if this awesome capability were not a monopoly but rather shared across two or more galactic superpowers, Darwinian instincts could naturally come into play and drive their respective peoples into conflict.

"It does seem likely to me that the idea that 'intelligence' as an adaptation to environmental variation should be pretty general." For now, no one has detected any Type II civilizations, nor any Type IIIs, either, which means they probably aren't currently active -- scientists say that if they were, they and their detritus would simply be too sprawling to miss. Kaku has said Earth might reach Type III in five millennia. But the Kardashev civilizations would confront another inescapable geopolitical conundrum, one that has to do with basic physics. Whether these ultra-advanced technological societies are using fossil fuels, fusion, or perpetual motion to power themselves, they would face the second law of thermodynamics, which states that when you produce energy, there is always waste heat -- meaning pollution.

That is, every technological society will be forced to confront climate change. On Earth, that has meant drought, fire, hurricanes, and sheer volatility -- subjecting the planet, its nations, and population to a very different risk and wealth profile. Some of history's greatest changes of power and fortune have capitalized on chaos, and climate change is ultimately a chaos event. Not all planets with technological societies will experience a climate shift like the Earth's, nor its particular reverberations. Out there, extraterrestrials may never have pushed their circumstances to the brink, as humans have. But there is no escaping the calculus of climate. In a 2018 paper, the University of Rochester's Frank and several coauthors modeled three likely climate change scenarios for alien civilizations. Only one could be characterized as positive: a soft landing as an extraterrestrial society quickly scaled back carbon-based fuels. The other two outcomes result in civilizational collapse, either rapidly if no attempt is made to switch to non-carbon energy sources, or slowly if that effort comes too late. Frank's work contains obvious warnings for technological aliens: An abrupt change in climate some 60,000 years ago pushed Homo sapiens from East Africa first into Asia and then Europe, where they met the

Neanderthals and Denisovans who had preceded them and were quickly out-competed, as the astrobiologist Lewis Dartnell writes in his 2019 book Origins. Drought in the fifth century A.D. led the Huns across the steppe west, helping to trigger the climactic fall of the western Roman Empire. The Little Ice Age that began in the 14th century caused crops to fail, triggering famine and disease, which destabilized cities and whole kingdoms, including China's Ming Dynasty. All of these events were either made possible or set off by tectonics.

Now the challenge facing Earthlings is the buildup of carbon dioxide in the atmosphere, which is at its highest level in 3 million years. It will be the same for technological aliens. "If you are a civilization and using energy, you will drive your planet into a climate change era," Frank said.

Scientists draw some portraits of the probable shape of an alien society. Geoffrey West, of the Santa Fe Institute, says intelligent alien beings would congregate in a place that would strikes us as a city -- "something that had structure and a built quality." Nicholas Wright, the neuroscientist, said these beings would have a policing mechanism, although not necessarily a police force as we know it, because order is one of the main features of life. And Frank said they would have done what they could to mitigate the impact of natural disasters like earthquakes. Jack Goldstone, a professor at George Mason University, suggested that if the city were part of an intelligent agrarian society on its possible way to technological status, the historical cycle there would be somewhat predictable.

"They will prosper, then stagnate and decline, for many thousands of years, without making any steady progress or breakthroughs to modern science," he said, noting how tricky the jump to industrialization and modern science can be. Loeb, the Harvard professor, agrees that this may be the case, but adds that the forces behind history are many. The population of this city may be exceptionally brighter than humans, since they may have existed for billions of years as a technological race compared with our mere hundred or so.

Human history has drawn a stark evolutionary line between mere intelligence and technological society. During the Cambrian explosion a half-billion years ago, the Earth -- perhaps newly sprouting oxygen-producing plants and algae -- suddenly erupted with a diversity of animals. The first humans appeared 200,000 to 300,000 years ago, and urban civilization just 3,500 years ago. The ingenuity displayed by humans in those millennia added almost nothing to the economic quality of their lives, which on average was relatively static until the 16th century. Then a radical social and intellectual shift triggered humanity's transformation into the technological species we are now. The period began with profound scientific breakthroughs across multiple disciplines and then, in the 19th century, a decisive break from the past with the Industrial Revolution. The rest has been the scientific and technological era that we think of as modern humanity.

In other words, the post-Copernican age to which all of us are accustomed makes up merely 0.0000001% of Earth's 4.5 billion years. Everything else led here. But for a political turn in this or that moment of time, we might still be the anti-scientific, medieval minds we were not very long ago. Goldstone, the George Mason professor, thinks this Darwinian pattern will hold across all possible intelligent civilizations in the universe. The combination of factors that resulted in Earth's scientific and industrial revolutions, and their resulting geopolitical impacts, obviously can and do happen. But judging by the paucity of evidence so far of other technological races, they are very much the exception, he said. "Most civilizations on Earth didn't get anywhere near to modern science," Goldstone said. "Pharaonic Egypt, Babylonia/Persia, the Roman/Byzantine Empire, and China didn't appear to be making any progress toward modern science."

What made humans punch through to the next level? The cutthroat school of evolution, suggested Peter Richerson, a professor emeritus at the University of California, Davis. It was adversity -- the contest among genes confronting, through their host organism, the reality of the Earth -- and lots of it. Our development was fundamentally driven by the volatility of the climate, changes in the atmosphere, violent tectonics, and other hardship that forced adaptation. The idea is that when stuff like the bad times of the ice ages came really fast and hard, human brains grew and grew. Over 2 million or so years, since the Stone Age Homo habilis, our brains have doubled in size.

It should be the same elsewhere, whether you are born on Earth or Wolf 1061c, a potentially habitable planet 13.8 light-years from our solar system. "It does seem likely to me that the idea that `intelligence' as an adaptation to environmental variation should be pretty general," Richerson said.

The drive to know the beings we may be sharing our galaxy and universe with is in a way a response to Fermi's question. He wanted to find out where the aliens are, but, given a chance to rephrase his question today, he might easily add, "And what are they doing?" Yet even if Fermi's lunch had never occurred and he did not address space's seemingly missing inhabitants, we would doubtlessly still be looking for some neighbors to talk to out there. We would want to know what they are all about. Humans are fundamentally explorers -- we populated the Earth pushed partly by this impulse, a reach for more, and have gone out into the solar system on the same quest.

Drake thinks that if a civilization is sending out radio or light signals in hopes of capturing the attention of another society, it will suggest a benign bent. Such aliens will be eager to help less technologically advanced societies.

There are also the matters of life and death. War, peace, and great power rivalry are the eternal geopolitical questions. Humans have always tended to cohere into groups. Society is defined by such natural clustering into what we sometimes loosely call tribes. When these tribes have rubbed up against one another, that's where Darwin has come in. Do they cooperate or compete? If it's the latter, it has often led to war, frequently over the control of resources and the territory on which it's located. Goldstone said that tribes of all sizes, whatever planet they grow up on, will be inclined to expand to the next geographic border or equally powerful state. Whether that leads to war there could depend on the planet's own history. One line of thought is that -- in the case of colliding extraterrestrial superpowers -- you would avoid such physical confrontation only if one or both step back from their base Darwinian instinct.

If they exist, the beings on K2?72 e, the potentially habitable exoplanet, will exhibit cooperation and competition, traits highly particular to tribes. Like them, the inhabitants of Teegarden b will doubtlessly find themselves migrating in substantial numbers from time to time, compelled to by the forces of plate tectonics, such as the occasional volcano or drought. There could be friction if the migrations are to the home of their possible neighbors on Teegarden c, with whom they seem very likely, by the trends springing from natural selection, to be rival powers -- especially if they are doing so in high numbers.

Frank Drake said that when he began his work decades ago, the positive, internationalist aura of postWorld War II politics still prevailed, making people believe that since "the good civilizations had all won and the bad guys lost, the forces of good would always win." When he and other alien hunters extended that line of thought, they assumed most technological civilizations would be good guys, too.

Recent politics make Drake question his assumptions. But he still thinks that if a civilization is sending out radio or light signals in hopes of capturing the attention of another society, it will suggest a benign bent. Such aliens will be eager to help less technologically advanced societies.

Two weeks ago, Avi Loeb traveled to Paso Robles, a wine-growing California town about halfway between San Francisco and Los Angeles. A group of big-name scientists were meeting to talk about one of the highest-stakes, longest-shot space projects in the world. It is an effort to launch the first space probe to an exoplanet -- Proxima Centauri b, four light-years from Earth. The aim, Loeb said, is to learn whether a technological alien civilization lives there.

Loeb chairs the group, which calls itself Breakthrough Starshot. Its participants are a who's who of space science, including Freeman Dyson, of the Dyson Sphere; Pete Worden, former director of the NASA Ames Research Center; and the Nobel laureate astrophysicist Saul Perlmutter. Facebook CEO Mark Zuckerberg sits on the board with Loeb and, until his death two years ago, so did the theoretical physicist Stephen Hawking. The Russian billionaire Yuri Milner has seeded it with an unusually lavish $100 million budget as part of a larger space initiative.

The idea is to use a blast of lasers from Earth to give massive propulsion to a "light sail," a vehicle a few square meters in size that would be waiting in space. Weighing a single gram but containing shelves worth of science and communications technology, StarChip, as the light sail will be called, would be accelerated to a fifth the speed of light, more than 37,000 miles per second. Given that Proxima Centauri b is 4.24 light-years from Earth, part of the Alpha Centauri system of stars, StarChip will still require 20 years to get there, and the scientists reckon they will first need 20 years to fully develop StarChip and the propulsive lasers. All together, that would put arrival at Proxima Centauri b in around 2061. We would receive the news in 2065, since any message back would travel at the speed of light.

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