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|The Fermi Paradox and|
Cons & Events
by Ian Douglas
That, in a famous and possibly apocryphal story, was the question asked by physicist Enrico Fermi over lunch with several of his associates back in 1950. It became known as the Fermi Paradox, and explaining it is one of the nastier challenges for people who, like me, believe that intelligence is common, or should be common, throughout the cosmos. In other words, if life is as common throughout the universe as we think it is, as it ought to be, why is the sky so resoundingly silent?
Fermi’s question argues from three basic assumptions—mediocrity, scale, and a concept given voice in a somewhat different context by Michael Crichton in Jurassic Park: “Life will find a way.”
The Principle of Mediocrity has been a cornerstone of scientific philosophy since Copernicus overturned the Geocentric Hypothesis. As far as we can tell, we live on a quite typical world in a typical solar system in a quiet corner of a typical galaxy. From a Darwinian perspective, intelligence seems to confer a survival benefit; Homo sapiens exists today because our remote ancestors were good at brainy activities like figuring out how to use femurs as clubs, sharpened bits of flint as knives and scrapers, and fire for evicting cave bears from desirable real estate. If we could do it, others could. The Mediocrity Principle states, unequivocally and in rather humbling terms, that there’s nothing whatsoever special about us.
The argument from scale points out that there is a lot of room out there within which the Mediocrity Principle can be applied. Current star-count estimates suggest that our Galaxy consists of 200 to 400 billion stars; split the difference and call it 300 billion. In our presumably mediocre solar system, we have eight planets (pace, Pluto); since 1988 our detection methods have been good enough that we’ve begun discovering planets circling other stars. As of February, 2008, the count is up to 271 exoplanets, planetary worlds in other star systems, and more are being found every month. As a result, conservative estimates hold that one star in ten will have planets ... and the actual percentage may be much higher.
That’s thirty billion solar systems in this galaxy alone.
And most star systems will have more than one planet, remember. Our list of exoplanets is a bit skewed right now, due to the fact that we’re better able to spot big, massive planets—giants bigger than Jupiter—than we are able to detect gravel like Earth. Even so, twenty of the stars known to possess planets have more than one planet, and it’s a good bet that all of them do. Our own Solar System currently boasts twenty-four planemos, or “planetary-mass objects.” That’s eight full-fledged planets and sixteen dwarf planets, including the four largest planetoids, former-planet Pluto, and frigid newcomers to the list out in the Kuiper Belt like distant Eris and Varuna.
Count on it. Thirty billion star systems in our Galaxy will translate into hundreds of billions of planets.
But there’s a second aspect to scale, and that’s time. Our Sun is, again, a fairly average star about halfway through its expected Main Sequence lifespan, while Earth itself is 4.6 billion years old. That makes us the new kids on the block. It’s been 13.7 billion years, plus or minus 200 million years, since the Big Bang that created the stuff of the universe—galaxies, stars, planets, and you. Earth has been here for only one-third of the total span of the universe.
As it happens, though, one of those 271 extrasolar planets is PSR B1620-26c, a world twice the mass of Jupiter circling a double star (a white dwarf and a pulsar) in the globular star cluster M4, in the constellation of Scorpius about 5,600 light years from Earth. The denizens of globular clusters are very old stars, among the first to emerge from the chaos of the Big Bang; astronomers have concluded that PSR B1620-26c may be 12.5 to 13 billion years old, a most respectable age that puts it within spitting distance of the Big Bang itself.
The Principle of Mediocrity suggests that, in all likelihood, roughly half of all of the Galaxy’s star systems are going to be older than Sol’s, while the other half, roughly, will be younger. PSR B1620-26c proves that some of those worlds are going to be lots older.
And that brings us to the final argument of the triad—the idea that life will find a way. Anyone who’s battled mildew on a damp wall or cockroaches in the basement will tell you that life is tenacious. Earth’s fossil record suggests that just six hundred million years after the planet coalesced from the solar nebula, almost as soon as the planet possessed a solid crust and liquid water, in fact, the first bits of self-replicating carbon chemistry that might be termed life were adrift in tidal pools or clinging to the sides of deep-ocean thermal vents. Once started, there were plenty of crises and turning points—asteroid impacts, mass extinctions, global ice ages, global greenhouses—but always life managed not only to hang on, but to continue developing, adapting, and expanding into new habitats.
And a mere four billion years later, there was us.
Today, we can find bacteria adrift in the winds atop Mt. Everest and at the bottoms of the deepest ocean trenches. We have found thermophilic organisms happily dwelling in boiling springs, metabolizing sulfur around deep-sea volcanic vents, metabolizing methane in freezing water, growing inside ice cores taken from beneath the Antarctic ice cap, and growing in such numbers in the planetary crust kilometers deep that intraterrestrial life may out-mass all other living organisms on the planet combined.
So—stars have planets as naturally as cats have kittens. Planets develop life as soon as conditions are right ... and we’re just now beginning to realize that the range of potential right conditions is far wider than we’ve ever before imagined was possible. Until recently, the assumption was that life could only evolve in the so-called Goldilocks Zone, a region around the parent star neither too cold nor too hot for liquid water and, hence, life. Since the 1980’s, however, it’s been clear that we may not need to find a second Earth to find life. The evidence suggests that Europa, one of the moons of Jupiter, has an ocean of liquid water locked away beneath the ice, one that may hold more water than all the oceans of Earth. Lately, some astrobiologists have suggested that intralithine microbes or deep-crust bacterial mats could exist beneath the Martian surface, safe from the ultraviolet radiation sterilizing the surface.
And that’s just looking at what we recognize as life ... carbon-based and with water as a vehicle. There’s always the Dr. McCoy Observation: “It’s life, Jim, but not as we know it.”
We don’t yet know if intelligence is an inevitable outcome of an evolving ecosystem—the smart money says it is not—but with hundreds of billions of worlds and twelve billion years to play with, what do you think? Right here on Earth, a decent definition of the word intelligence suggests that reasoning and problem-solving abilities evolve naturally, even inevitably. Great whales and dolphins, of course, are the New Age favorites, but there are others. Elephants—who have been known to pack mud into the bells strapped to their legs so that they could raid village gardens without sounding an alarm. Octopi confronted with crabs inside screw-cap jars. Bonobo chimps, mountain gorillas, and African Gray Parrots, all of which have been shown to use language in apparently intelligent and rational ways.
Darwinian evolution seems to select for greater and greater complexity in order to offer more possibilities in adapting to or overcoming a hostile environment, and now Darwin appears to have extended his blessing to intelligence as well.
Even if the dream of faster-than-light travel forever remains impossible, an absolute barrier created by the physics of the universe, it seems likely—hell, it seems inevitable—that life has evolved on an unknown but high percentage of those billions of planets, and that some percentage of those alien ecosystems evolved intelligence. This is the basis for the famous Drake Equation, which attempts to find boundary-numbers for technical and communicative extraterrestrial civilizations. What percentage of stars have planets? What percentage of planets evolve life? What percentage of life-bearing worlds develop intelligence, and what percentage of those develop technology, a desire to communicate, and manage not to blow themselves up? Early attempts to fill in the Drake Equation’s blanks were frustrated by our ignorance both of the likely number of extrasolar planets, by ignorance of the range of possible life-friendly habitats, and by the very human assumption that both life and intelligence had to be like our kind of life and intelligence.
With the discovery of hundreds of extrasolar worlds, we can be somewhat confident that some millions of intelligent species have evolved within our Galaxy alone, at the very least.
As opponents of the life-is-common school suggest, of course, there are plenty of reasons why there may not be millions of species out there now. Maybe there’s a limit to how long a technical species remains technical. Maybe intelligence isn’t as good a long-term survival mechanism as we like to think; we still live within the shadow of thermonuclear annihilation, after all. And in the long run, planetary surfaces aren’t all that safe for an evolving species. Just in the past billion years, terrestrial life has had to contend with global warming, global freezing, periodic impacts by planetoids or comets, massive volcanic outgassing, instabilities within the local star, the appearance of poisonous gasses like oxygen ... hell, maybe it’s a miracle, literally a one-in-a-hundred-billion chance, that we’re here at all.
Nor does intelligence necessarily imply technology; look at elephants and dolphins, two excellent candidates for non-human intelligence right here on Earth. They seem happy enough without cell phones or video games. Or maybe intelligent life tends to play with fire, chipped flint, and nuclear weaponry for a few thousand years, then sink into a self-contented, navel-contemplating torpor. Maybe most intelligent species never get to the flint-chipping stage, or are marine species who never develop fire and technology. Or maybe most go from fire to video games to artificial worlds of virtual reality where they don’t interact with the rest of the universe at all.
The joker in the deck, though, is that word most. Out of some millions of intelligent species, does every single one annihilate itself after a few thousand years of productive flint-knapping? Or decide technology was a bad idea and go back to living in the trees? Or lose itself in the joys of Internet sex?
Consider, if just one intelligent species out of all those millions develops the technology to leave the surface of the world of its birth, if it begins to develop the seemingly inexhaustible resources of its solar system, and—like the life we know—begins moving outward, seeking new habitats, new resources, or simply to rubberneck because they have our sense of awe and wonder. If just one species decides that planetary surfaces are a bad place for factories or industrial pollution, or too susceptible to cometary impacts, and goes on to do something about it ...
Even with spacecraft capable of no more than one tenth of the speed of light, they could conceivably explore and colonize much of the Galaxy within a mere hundred million years or so. That’s a heartbeat compared to the age of some of the worlds out there.
The Principle of Mediocrity, the scale of time and space, and the fact that life seems designed to move into and exploit new environments all suggest that the Galaxy has been explored and colonized again and again and again throughout the past eight billion years or so. Think of it. Billions of alien James Kirks boldly going where billions of carbon-based life forms have already gone before....
And yet ... the sky seems so damned empty.
Fermi’s Paradox. Where are they?
Today, we listen in on the sky with radio telescopes, searching for a whisper, a hint, a fragment of an alien I Love Lucy, anything that might suggest another communicative, technologically proficient species out there among all of those billions of stars. Well, maybe we’re using the wrong tools, the critics suggest. Our own species has only possessed radio for a century or so, and maybe in another century or less we’ll discover something that makes radio about as useful for modern communicative purposes as banging a stick on a hollow log.
Maybe. But radio is cheap and easy to discover—a natural outgrowth of learning how to use electricity and magnetism—and if you were interested in discovering or even speaking with primitive cultures, the radio spectrum would be a good place to start. Not every advanced race is going to want to communicate with primitives, but if even one, out of those millions, was in a talkative mood ...
And quite apart from deliberate attempts to communicate with others, if your species survives long enough, what might it not be capable of? Englobing your local star with habitats to trap and use as much energy from that star as possible? Rearranging stars, or interfering with their chemistries, for purposes ranging from the practical to the esthetic to the unimaginable? Sending Von Neumann probes into other star systems to rework lifeless planets into useable real estate? Or sending out clouds of Bracewell probes, spacecraft piloted by extremely sophisticated (and patient!) AI minds, equipped with a history of the sending culture, and the capability to monitor worlds for signs of intelligence, and learning how to communicate with it? It turns out there are plenty of ways to make yourself known to the rest of the Galaxy.
Assuming the first intelligent life evolved in our Galaxy four billion years after the first planets formed, they’ve had eight billion years to work things out.
Where are they?
I’ve been exploring just this question in three SF trilogies, published by Avon/Eos: the Legacy series, the Heritage series, and, most recently, the Inheritance series. And the answer to Fermi’s Paradox I’ve developed for these nine books has some rather chilling implications.
Suppose life does spawn intelligence almost routinely, and intelligence, in turn, goes to the stars. So far, so good.
But suppose just one of those star-faring species carries with it a Darwinian imperative from a predator-infested birth-world. It survived on its homeworld by wiping out every other species that presented itself as a threat.
That’s not all that far-fetched. Look at us. It’s possible that we survived because we were able to wipe out the competition—including cave bears, saber-toothed cats, a twenty-foot dragon-lizard called Megalania that was waiting for our ancestors when they reached Australia 50,000 years ago, and our own spear-wielding Neanderthal cousins. And right here around the hearth fire of modern civilization, there are plenty of folks willing to kill you because your skin’s the wrong color, you worship the wrong god, or you embrace the wrong political system. Xenophobia is a valid survival tactic. Not a pretty one, mind you, but valid.
So ... supposing just one species out of all those millions makes it out among the stars with phasers set on xenophobic genocide. If they come out on top because they’re the most ruthless, the most vicious, the most successful competitors out there, they’re going to wipe out everyone else, and they’re going to dictate the appearance of the Galactic panorama ... at least until someone even more vicious comes along.
The sky is quiet because everyone has been hunted to extinction except the hunters.
In the Legacy, Heritage and Inheritance universes, the xenophobes are called the Xul. It seems they made an impression on the ancestors of the Sumerians about eight thousand years ago, and Xul is the Sumerian word for demon.
Demons in the night. The Hunters of the Dawn.
If they’re out there, they’re the answer to Fermi’s Paradox. They’re well-established and widely scattered, with listening posts positioned every few tens or hundreds of light years, so that no more than a century, say, will pass between the sending of a radio signal, and their receipt of it.
They’re listening, watching, and waiting for some sign, any sign, of a possible competitor who is just beginning to play around with technologies like space travel, nuclear weapons, or radio. Their technology may be billions of years ahead of ours, but they know that if we get out there and get established, we may, some day, pose a threat to their survival. Maybe it’s not even that personal. Their tendency toward genocide might be truly Darwinian, an adaptive instinct of which they’re not even aware.
But they’re hard-wired to hunt us down and wipe us out before we learn enough to move from mostly harmless to dangerous.
Our first radio broadcasts are en route to the stars as we speak, followed closely by I Love Lucy, American Gladiators, and reality TV programming.
We’ve already pounded on the front door, and now we’re waiting to see just who is going to open it, and what their mood might be....
All text copyright (c) William H. Keith