I know Fermi paradox is a popular topic, but when I saw the POB word of the week to be paradox, I couldn't help myself as this is my favourite paradox.
Fermi Paradox - what is it?
It all started with a casual conversation at lunch, with Enrico Fermi (who was a physicist and some colleagues), discussions varied amongst the physicists, and discussion about faster than travel light came up, and much later, Fermi came up with the outburst... "but where is everybody?"
So why did he say this? well, if faster than light travel was possible then shouldn't we be have been visited by aliens already?
But the implications are broader than just faster than light travel, it comes down to life itself, and how rare life is, according to some, the probability that life exists elsewhere is so astronomically high that its almost certainty. This usually arises out of an analysis of the drake equation, which looks at the number of stars in the universe, and then how many planets around those stars and then chance of life starting, and then evolution to intelligent life.
but all this deeps mathematical analysis on probabilities are cut down by three words, "where are the aliens"
Because if life is such a certainty, then we should have met aliens by now.
Arguments to explain Fermi Paradox
Well, so in order to reconcile the near certainty of the drake equation and the probability of life, and the fermi paradox a number of explanations are possible.
- Faster than light travel is impossible, so they can't reach us
- Civilizations blow themselves up with nuclear weapons before reaching out to the stars
- The chance of life evolving from nothing is near zero
- the chance of evolving intelligent life from life is near zero
Lets have a look at each of these
Faster than light travel is impossible, so they can't reach us
even if faster than light travel is impossible, generation ships could be built and quite possibly it might take 100 years to travel a light year, but even then over millions of years the civilization could explore the whole galaxy, so this doesn't seem like an answer.
Civilizations blow themselves up
I don't think this is a credible argument for the Fermi paradox, as some civilizations might, but all? this seems quite implausible. Also we as the human race are not very far off becoming an interplanetary species, and we have had nuclear weapons and other technologies for almost 100 years, so its likely we might get through this period ourselves.
The chance of life evolving is near zero
This is interesting, and we haven't yet found life starting out anywhere else apart from earth, and even on earth all organisms that have survived so far can be traced back genetically to the same basic forms of life. So its is possible that the probability of life starting is astronomically small (aka infinitesimal), and earth is the only place its happened, I personally don't buy this, as random experiments with electricity and primitive earth atmosphere have shown amino acids do form quite easily in this environment.
The chance of intelligent life forming is near zero
This is harder to understand, we can see that evolution seems to be a natural process, that life evolves too, but does it always create intelligent life...I must admit I don't have a view on this, but interested in yours.
Conclusion
So on the one hand, the vast number of extra solar planets and galaxies and stars is so big, that it almost seems certain that life exists, but where are the aliens, all logically thought concludes that we should have met them by now, so its a really puzzling thing, and perhaps life is unique, and perhaps not... and we will meet aliens in the future? I look forward to all the future astrobiology discoveries that are bound to come up in the future.
Sources: Eric M. Jones "Where is everybody, an account of Fermi's Question"