Nick Bostrom’s written a fascinating article about why he hopes the search for extraterrestrial life yields nothing.
Basically it comes down to the idea that if we discover the remains of some kind of life, then life is not as statistically improbable as we might like to think it is. And if it’s not that statistically improbable, then why haven’t we already been visited?
One possibility is that by the time a civilization has developed the technology to colonize space, they manage to destroy themselves first. Or eco-disaster wipes them out. Or whatever. The point is that a Great Filter lies ahead, a hurdle we’re extremely unlikely to leap over.
Of course, if we find nothing, we’ve got nothing to worry about. For now.
Anyway, it’s an interesting read.
The coolest thing in it that I’d never heard of: Von Neumann probes, a theoretical self-replicating spacecraft for colonizing the universe.