If aliens exist, why are they not here?
The speed of light limit is NOT the answer to this question - you see, an intelligent species can colonize the entire Milky Way in a few tens of millions of years and the galaxy is BILLIONS of years old.
As I see it, it may be a case that life (if it exists anywhere besides here) is not evenly distributed throughout the universe. I mean, look at the Earth, life is not evenly distributed whatsoever, though life can survive in the most unusual (from our perspective) locations. What's to say that Earth is one of the few outposts of life in our galactic/universal neck of the woods.
I find the assertation that an intelligent species can colonize the entire Milky Way in the timeframe available somewhat...unhelpful, since it implies it's the only thing that will happen with an intelligent spacefaring race. A timeframe of billions of years for the Milky Way's existance is enough time for a galaxy spanning civilization to collapse and all evidence wiped out by the passages of time. (see the amount of sci-fis with this concept of resurgences of intelligent species and it happening in cycles?)
It could be perfectly reasonable to suppose that we could be at any point in this 'cycle' where intelligent life is only restarting it's journey across the stars, and hence there is either:
-no one yet to meet out there, humanity could be the 'first', this time round.
-intelligent life is out there, we're just in a bit of a backwater and yet to be found.
The worst bit could be finding out that humanity is the first species to be hitting the stars out of this galaxy, and it's a sparsely populated, or totally uninhabited, and everywhere else is teeming with life.
It's a big place, the universe, anything is