McFreedom

I've just finished redding If the Universe Is Teeming with Aliens... Where Is Everybody? Fifty Solutions to Fermi's Paradox and the Problem of Extraterrestrial Life, by Stephen Webb. It's a fairly interesting book, although it has some very long detours into things like basic biology which I'm not sure are all that germane to its central thesis, and most readers of a book like this should probably know, anyway.

For those unfamiliar with Fermi's Paradox, it goes something like this: If life in this galaxy is common, given that the galaxy is about 8 billion years old, and life on Earth about 4 billion years old, life should've existed in the galaxy for at least six or seven billion years. And intelligent life should be at least four billion years old (assuming our development is average). Even assuming faster-than-light travel is impossible, an intelligent species could colonize the entire galaxy (with colonies creating their own subsequent colonies) in well under 5 million years. The question is not just as simple as "why have aliens not landed here?" More profoundly, it is "why did aliens not colonize the Earth long before life arose here?" A similar dilemma is beginning to arise out of SETI's work: If intelligent, technological races are common in the galaxy, how come we never hear them using radio?

Mr. Webb's book tackles both of these questions, offering most of fifty answers which attempt one or the other, and a handful which attempt to answer both. Most striking to me is the litany of potential disasters which might have befallen other, potentially intelligent peers. In addition to the obvious massive asteroid strike, we can add the Earth's moving out of the surprisingly narrow habitable zone in which water is neither ice nor steam and radiation from a nearby supernova; in addition to more prosaic disasters such as disease and those of our own making.

All ET speculation boils down to two basic camps (outside the fringes of UFOlogy, of course): Either they're out there, and we can't find them (which ignores the question of why they didn't colonize Earth before we evolved), or we're basically it. It first became possible to really begin studying these topics with the advent of radio telescopy in the 1950s; it was widely assumed that evidence for Little Green Men would be forthcoming soon. But, after fifty years of research - admittedly less than eyeblink in the age of the galaxy - one must begin to wonder if, in fact, we are alone.

The solution that Mr. Webb favors is a combination of disappointment and disaster. He suggests that the values we should plug into Drake's famous Equation are small ones: "Earthlike" planets are uncommon within the water band, or many Sol-like systems may not have Jupiters to sweep asteroids out of the inner solar orbits. Life may develop frequently but not have a 4 billion-year run all that commonly due to the likelihood of massive climate change; vast swaths of life were eliminated on this planet five times in our history - had things been a little worse, it's not inconceivable we wouldn't be here at all. Of those with intelligent life, technology isn't all that common, either because the intelligence dies or, in fact, there is something unique about the human mind.

Regardless of the reasons, Mr. Webb predicts that the final number in the equation - N, the Number of communicative civilizations in the Milky Way is 1, us. I think the jury is still out on this - we are still learning so much about cosmology, space science and exobiology that it is in no way inconceivable that we'll turn up a nearby twin of Earth - complete with intelligent life - in the next fifty years. But, at the same time, our poor luck in finding our soul mates is becoming puzzling, enough so that we might indulge ourselves a little in thinking what it might mean if we did, in fact, win the cosmic lottery and are the sole tenant in a 50-billion-star multi-unit dwelling.

Such a finding should give us a dramatic sense both of how valuable human life is, and how fragile it is. Right now we are clearly vulnerable to planet-wide catastrophe, and we're beginning to suspect that may not be as unlikely as we'd like to hope. We are similarly vulnerable to system-wide catastrophe, which also may be more likely than we'd like to think. To preserve our nearly unique intelligence, we need to get self-sustaining settlements on other planets in this system as soon as possible, and be working on some sort of interstellar colonization as soon as we can.

Of course, may environmentalists consider us to be a plague upon this planet, and are not interested in our infection being spread to other - even lifeless - planets and solar systems. To which I query: If every other intelligent species in the 8 billion year history of the galaxy has failed to survive as long as we have...doesn't that make mankind the most endangered species of all?

UPDATE 02/18/04: Corrected for clarity, a mispelling and a math error. Nothing substantive.