Quote:Given the fact that there are perhaps 400 million stars in our Galaxy alone, and perhaps 400 million galaxies in the Universe, it stands to reason that somewhere out there, in the 14-billion-year-old cosmos, there is or once was a civilization at least as advanced as our own. The sheer enormities of the numbers almost demand that we accept the truth of this hypothesis. Why, then, have we encountered no evidence, no messages, no artifacts of these extraterrestrials? Webb discusses in detail the 50 most cogent and intriguing solutions to Fermi's famous paradox: If the numbers strongly point to the existence of extraterrestrial civilizations, why have we found no evidence of them?