Publisher's description: During a lunchtime conversation at Los Alamos more than 50 years ago, four world-class scientists agreed, given the size and age of the Universe, that advanced extraterrestrial civilizations simply had to exist. The sheer numbers demanded it. But one of the four, the renowned physicist and back-of-the-envelope calculator Enrico Fermi, asked the telling question: If the extraterrestrial life proposition is true, he wondered, "Where is everybody?" In this lively and thought-provoking book, Stephen Webb presents a detailed discussion of the 50 most cogent and intriguing answers to Fermi's famous question, divided into three distinct groups: Aliens are already here among us. Here are answers ranging from Leo Szilard's, that they are already here and we know them as Hungarians, to those who claim that aliens built Stonehenge and the Easter Island statues. Aliens exist, but have not yet communicated. The theories in this camp range widely, from those who believe we simply don't have the technologies to receive or interpret their signals, to those who believe the enormities of space and time work against communication, to those who believe they're actively hiding from us. Aliens do not exist. Here are the doubters' arguments, from the Rare Earth theory to the author's own closely argued and cogently stated skepticism. The proposed solutions run the gamut from the crackpot to the highly serious, but all deserve our consideration. The varieties of arguments -- from first-rate scientists, philosophers and historians, and science fiction authors -- turn out to be astonishing, entertaining, and vigorous intellectual exercises for any reader interested in science and the sheer pleasure of speculative thinking