I have always been bothered by the seeming perplexity that people have about the fact that we have yet to encounter intelligent life beyond planet Earth. It doesn't seem weird to me at all, even though I suspect life--even intelligent life--is not that uncommon in the universe. Enrico Fermi--a great physicist from the mid-20th century-- expressed the perplexity that many people have in what has come to be known as the "Fermi Paradox." At its most simple, the paradox is this: if the development of intelligent life is even moderately likely, why haven't we seen evidence of intelligent life elsewhere...