[ExI] for the fermi paradox fans

[BillK]

On Tue, Jun 10, 2014 at 6:01 PM, John Clark wrote:
> When you look at a picture like that or the Hubble Ultra deep field
> http://wallpaperpanda.com/wallpapers/jio/ekA/jioekAKKT.jpg  we know that
> even the smallest dots in it are not stars but galaxies consisting of
> millions or billions of stars, and yet we also know that life can not exist
> anywhere in that picture. We know this for 2 reasons:
>
> 1) This picture is of things as they were only a few hundred million years
> after the Big Bang, and that's not enough time for life, much less complex
> intelligent life, to evolve.
>
> 2) There wasn't even enough time for stars to cook up the elements that life
> needs, life Carbon or Oxygen or Nitrogen; what you're looking at in pictures
> like that are just Hydrogen and Helium and a very very small trace of
> Lithium. And you can't do much interesting chemistry with nothing but that.
>
>

That's correct. But the point of that photo is to impress us with the
unbelievable size of the universe. Life will almost certainly have
happened in these galaxies in the intervening billions of years since
the original photons started their journey towards us. We will never
detect it, but we now know the huge size of the small part of the
universe within our light cone.

The Fermi paradox concerns our own galaxy. Why hasn't our galaxy been
colonised already? Where are the signs of life in our galaxy?  Where
is everybody?

Whatever they are doing must be pretty fascinating to keep them so quiet.  :)

BillK