In October 1992, on the occasion of the 500th anniversary of Christopher Columbus' arrival in America, the US, space agency NASA launched a major project to search for extraterrestrial intelligent life. Known by its acronym of SETI -- Search for Extraterrestrial Intelligence -- the project employs radio telescopes around the world to "eavesdrop" on thousands of target star systems in the hope of detecting radio signals of artificial origin.
Project Columbus, now renamed Project Phoenix, is the latest in a long history of attempts to find life and intelligence beyond the Earth. The idea that we may not be alone in the universe is not a new one. In the fourth century BC the Greek philosopher Epicurus wrote in a letter to Herodotus:
There are infinite worlds both like and unlike this world of ours. For the atoms being infinite in number . . . are