Strangely enough I don't remember having a thread in the science forum about this.

Anyway, here it is.

I've been doing a lot of reading about this in the last couple of days. I've always assumed that there was an abundance of life in our galaxy, just because of the numbers argument; 10^11 is a lot of stars. I also think the multiverse theory has a lot going for it, so I assumed that, due to basic probability, it was likely that we'd find ourself in a universe with a very large number of other sentient creatures.

However I started reading properly about the Fermi paradox yesterday, and I started to realise the numbers game is a bit naive when you consider the other evidence:

http://en.wikipedia.org/wiki/Fermi_paradox

I was struck in particular by the observation that, if only 1 civilisation gained sufficient technology and had sufficient interest, it would take only a few million years to send probes to every solar system in the galaxy; and given that intelligent life could have arisen at pretty much any time in the last 10 billion or so years, this begs the question: why haven't we been contacted if such life is common?

There's also the conspicuous lack of any radio contact.

So, that's some food for thought and the general direction I'm interested in at the moment.