Presents a detailed discussion of the 50 most cogent and intriguing answers to Fermi's famous question, divided into three groups: Aliens are already here among... » 

Presents a detailed discussion of the 50 most cogent and intriguing answers to Fermi's famous question, divided into three groups: Aliens are already here among us; Aliens exist, but have not yet communicated; and Aliens do not exist. The proposed solutions run the gamut from the crackpot to the highly serious. The variety of arguments turn out to be astonishing, entertaining and vigorous intellectual exercises for any reader interested in science and the pleasure of speculative thinking. «