Came across an interesting Gizmodo article on the Fermi Paradox, or the idea that given the statistics we know about habitable planets and Sun-like stars and the age of the universe and the speed of evolution, the universe should be absolutely overflowing with intelligent life, so where the hell are all the aliens? There are apparently a lot of different theories currently in play among top physicists and astronomers, and the article gave a good overview of them, from least-scary to most-scary.
http://gizmodo.com/the-fermi-paradox...ths-1580345495