The Fermi paradox
January 24th 2009 07:44
The Fermi paradox is the apparent contradiction between optimistic projections made from the famous Drake equation - which predicts that there should be hundreds of thousands of technological civilisations in our galaxy, even if only a small fraction of all planets within it are habitable, and only a small fraction of those have witnessed the evolution of intelligent life - and the lack of evidence for any such civilisations. Surely, if there are so many aliens out there, shouldn't we have detected their presence in some form or other by now? Some scientists have taken this cosmic silence as evidence that ET simply isn't there. Others have tried to resolve the paradox by devising some scheme in which these civilisations do exist, but where we're somehow overlooking them. In this fascinating lecture (titled "Why aren't the aliens everywhere?") by Seth Shostak, an astronomer who works with the SETI (Search for Extra-Terrestrial Intelligence) Institute, some of the possible answers to Fermi's conundrum are considered. To my mind, I think that the most plausible solutions - assuming that the galaxy is inhabited by beings with the capability of travelling interstellar distances - are those that try to find analogues of ecological processes limiting exponential growth, or that consider how some pieces of galactic real estate might be less valuable than others and that advanced civilisations tend to cluster around energy and resource rich areas and perhaps have little incentive to colonise elsewhere.
There is another possibility. This could be that the probabilities that for the emergence of intelligent life that have yielded high estimates for the number of technological civilisations are too optimistic. It could well be that the evolution of intelligence is exceedingly rare on those planets that do spawn life. In fact, it could be exceedingly rare for other "milestones of evolution" to occur even well before that, like the evolution of multicellularity and nervous systems. We might just happen to be the only planet in the galaxy (if not the universe) in which intelligent life emerged, part of that small subset of planets on which nervous systems have evolved, on the still small subset of planets on which multicellular organisms evolved, and so on. In that case, the galaxy could be teaming with life, just not the sort that is privy to producing electromagnetic emissions that could be detected by our radio telescopes.
So, what does everyone think? Can you think of your own resolution to Fermi's paradox? (a funny one I thought of was that that every civilisation eventually produces its own Large Hadron Collider and gets sucked into a black hole, but scaremongering aside, that's not at all likely to happen).
There is another possibility. This could be that the probabilities that for the emergence of intelligent life that have yielded high estimates for the number of technological civilisations are too optimistic. It could well be that the evolution of intelligence is exceedingly rare on those planets that do spawn life. In fact, it could be exceedingly rare for other "milestones of evolution" to occur even well before that, like the evolution of multicellularity and nervous systems. We might just happen to be the only planet in the galaxy (if not the universe) in which intelligent life emerged, part of that small subset of planets on which nervous systems have evolved, on the still small subset of planets on which multicellular organisms evolved, and so on. In that case, the galaxy could be teaming with life, just not the sort that is privy to producing electromagnetic emissions that could be detected by our radio telescopes.
So, what does everyone think? Can you think of your own resolution to Fermi's paradox? (a funny one I thought of was that that every civilisation eventually produces its own Large Hadron Collider and gets sucked into a black hole, but scaremongering aside, that's not at all likely to happen).
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