Thursday, July 26, 2012
Panspermia makes it more difficult because one answer heretofore is that the accidental linking together of enough items able to replicate themselves is so mathematically improbable that it is likely to happen no more than once per galaxy, perhaps once per universe.
But if any form of panspermia is correct, life is not only not that rare it must be comparatively common so that excuse goes.
The next best reason is the assumption that as our ability to manipulate energy and the environment grows our ability to destroy ourselves grows faster and that intelligent civilisations inevitable wipe themselves out.
I'll come back to that.
The only other alternative I can think of (& I am very open to ideas) is that some link in the chain other than the development of life is still so mathematically improbable in the rise to our present state that it is still in the around 1 per galaxy. I touched on that before in my essay Life, the Universe and Everything before I had looked at so seriously panspermia.I pointed to the fact that life appeared on Earth almost as soon as we had a surface cool enough to be solid. That is statistically unlikely if life is a random accident and exactly what we would expect if microbes are arriving here from space continuously. To quote myself
"0.5 bn years, or less, possibly much less for life to form.
1 bn to start photosynthesis
1 bn to develop a cell nucleus.
1 bn to produce multi-cellular life.
0.5 bn to get up to the reptiles.
0.2 bn to get to dinosaurs and mammals.
& 0.005bn - maximum time to get from the chimpanzees to us.
Looks to me like the difficult and improbable stuff wasn't the formation of life or the evolution of humans but the evolution of anything bigger than a microbe. Go figure."
So back to the "we're bound to wipe ourselves out" scenario. I have come up with a problem for that too. The human race is now at the stage where we are within decades, at most, of being able to build a civilisation of space settlements and within a century of being able to build a fully self sustaining O'Neill colony able to leave this solar system. If we hadn't been immersed in ecofascist Luddism we would probably be building the first part of that now.
When we have life off Earth the entire human civilisation cannot be destroyed by a planetary nuclear war.
When we have O'Neills able to go to other systems we cannot even exterminate everybody by novaing (my claim to fame) the Sun.
If we are within a century of that then, if alien civilisations were, or rather had been, in existence in substantial numbers at least some of them would have been bound to get a century or 2 beyond where we are now.
I don't say insist that such a civilisation would have got beyond the ability to destroy itself, though that might be the case. But I do say that to destroy itself it would have to produce some pretty spectacular side effects. A number of Novas in adjoining systems happening to stars that would not scientifically be expected to to go for billions of years would be the minimum of it.
Any society that aggressive/expansionist is not going to go quietly into that good night. The astronomers would have seen something sufficiently spectacular and anomalous to recognise, at least potentially, as intelligent action.
This is not an argument which would have been convincing during the cold war when we were quite clearly stuck on 1 planet with 50,000 nukes, but it is now.
Of course the same argument applies to any civilisation that survives and keeps growing. I don't necessarily mean growing at the 5% rate of humanity now - Growing at even a thousandth of a per cent, far slower than at any time in known prehistory would triple a society in million years - a mere eyeblink in the age of the galaxy.
I can conceive of what was a human type civilisation which had learned and done absolutely everything, though I think it would have to be a post human cybernetic one, which simply decided to switch off. But even that is a stretch.
I think, that though microbial life is very common, we are the first and only intelligent civilisation.