Tuesday, October 11, 2011

Keep Telling Yourself: It's Only a Cartoon ...

I very rarely disagree with XKCD's cartoons, but this one baffled me. The explanation here doesn't help.

Yes, I know, it's a cartoon, not a philosophical or scientific argument. But the cartoonist is very serious about his math and his science. And so much here is wrong.

I'm sure that gliding in a wingsuit like the one depicted is fun; I've fantasized about free flight myself, many times. But the invention of such toys hasn't interfered with humans' determination to keep fighting until we've rendered ourselves extinct, so you can't resolve the Fermi Paradox by postulating that intelligent species on other planets just got so caught up in self-powered flight that they never bothered to build spaceships or some kind of long-distance communication.

Oh yes, the Fermi Paradox. It points to the conflict between many scientists' conviction that because the universe is so vast, there should be some other intelligent, spacefaring, radio-wave beaming species out there. If they exist, some should have been around long enough that we on earth could have picked up their transmissions, and if they've developed faster-than-light travel, they should have found us and paid us a visit by now.

I used to go to the occasional observatory / planetarium presentation where an astronomer would talk about the chances of life elsewhere in the universe. After a couple of them, I realized that the numbers they would toss out ("If one in ten thousand stars has planets, and one in ten thousand of those planets are the right distance from their star and has the right conditions for the development of life, and life develops on one in five hundred, etc.") were sheer fantasy masquerading as science because a scientist was reciting them, and lost interest. We have no basis for assigning probabilities in this area, because we have no data. We know of only one star with a planet at the right distance and with the right conditions for the emergence of life -- this one. Until we know of a good many more, we can't assign any probabilities at all.

Various attempts have been made to explain why we have found no trace of other civilizations. What XKCD calls the Corliss Resolution, after a wacko who likes to jump from high places with his wingsuit, doesn't do the job. First, if (as the explanation says) it's more fun to fly than to do calculus, then everybody would be out jumping off buildings -- only we wouldn't have any tall buildings because flying/gliding is presumably more fun than building skyscrapers too -- and calculus would never have been invented.

Maybe XKCD is postulating not the invention of self-powered flight on all planets that harbor intelligent life, but the evolution of quasi-avian species on all such planets, that such species wouldn't bother to invent space travel because they were too busy flying, and no other intelligent species would evolve there. Remember the vast numbers of stars out there, just in our galaxy let alone beyond; remember that the case for life outside our solar system rests on those numbers, which make it reasonable to speculate that there must be some other earthlike planets and other intelligent species somewhere in the universe. In order to make the Corliss Resolution plausible, someone would have come up with a reason to believe that life on every other life-bearing planet is too happy gliding to do anything else. (I think it's interesting that XKCD writes of "space colonization" rather than "space exploration." Does he want us to be colonized by kindly ETs?)

This shoots down the motive of much (if not all) scientific speculation about life on other worlds: that the emergence of life on earth is not a one-in-a-jillion fluke, that other organisms like us exist, that we are not alone in the universe. Even if the Corliss Resolution did turn out to be true (and we'll never know if it is), it would mean that the earth is unique and human beings are alone. That might be a good thing, but it would be a devastating disappointment to the many science geeks who've been inventing probabilities for the existence of extra-terrestrial life, to convince themselves and others that it's out there; it would destroy a major pillar of their faith.