Or for a longer read, David Brin gives it an excellent and lengthy treatment in Existence [1]. He even works in an exhaustive analysis of the possible answers

Or for a longer read, David Brin gives it an excellent and lengthy treatment in Existence [1]. He even works in an exhaustive analysis of the possible answers to the Fermi Paradox, as well as possible events constituting The Great Filter. I won't give spoilers but it's definitely worth reading. [1] http://www.amazon.com/Existence-David-Brin/dp/0765342626/ref=sr_1_3?ie=UTF8&qid=1428283635&sr=8-3&keywords=existence