If the Universe Is Teeming with Aliens ... Where is Everybody?

Given the immense size of the universe, it is logical to assume that somewhere out there are intelligent life forms. With so many stars—maybe 400 billion in our galaxy alone—and galaxies—maybe 400 billion in the universe—there should be at least one civilization that's as advanced as ours. Either no extraterrestrial civilizations have ever formed or they've been destroyed before they could communicate with us. Perhaps they don't want to communicate with us because they're aware of our violent nature. The sheer enormity of the numbers makes it almost certain that we're not alone. So why haven't we found any evidence of them? It's possible that they live underground. Or perhaps it's because we've only been looking for radio signals; maybe they communicate using some form of communication technology more advanced than radio waves. In this significantly revised and expanded second edition, Webb explores in detail the (for now!) 75 most cogent and intriguing solutions to Fermi's famous paradox: If there are so many intelligent civilizations out there, why haven't we found any evidence of them?