Forbes has an article up noting that many scientists, including Seth Shostak, are now saying that we could find intelligent extraterrestrial life in the next twenty years. I definitely think we might find extraterrestrial life in that time frame, but I’m pretty skeptical that it will be intelligent.
I’ve written about this before, but the summary is that the universe is far older than our planet. There has been plenty of time for intelligent aliens to have evolved. But if they had evolved, they should have been here long ago. Indeed, we should have been colonized many times over. But there’s no evidence of that having happened. This is known as the Fermi Paradox. If all the statistics point to pervasive intelligent life, then where are they?
There have been lots of proposed answers to the Fermi Parafox, such as the rare earth hypothesis (discovering any other world with life would falsify this one), berserkers, interstellar travel is impossible or hopelessly impractical, and many others. Personally, I think the most likely scenario is simply that intelligent life is very rare, and that the nearest extraterrestrial civilization may be millions light years away. Too far away for any of them to have reached us yet.
Of course, there are more disturbing alternatives. It might be in the nature of intelligent life to destroy itself, we are living on borrowed time, and the possibility of us encountering another intelligent species in our mutually brief existences is remote. Or intelligent life might be pervasive, and we’re staring right at it, but like a troupe of monkeys unable to recognize the significance of buildings and machinery, we might be mistaking their technology for natural phenomena.
If intelligent life is pervasive, and some form of interstellar travel is at all possible, then it’s probably reasonable to assume they have probes in the solar system right now. Our first evidence of them may be when we stumble on one of their probes on Mars or in the asteroid belt. Although with a rich biosphere on the third planet, you’d think they’d have parked themselves somewhere close to observe, but who knows? (No, there’s no good evidence for UFOs.)
So, it won’t surprise me much if, in the next few decades, we find evidence of life on an exoplanet, or possibly even in our solar system. But I’ll be pretty surprised if it attempts to start a conversation with us.