Definition
The Fermi paradox, attributed to Italian physicist Enrico Fermi, concerns the apparent contradiction between the lack of any evidence for the presence of extraterrestrials on Earth and the view that extraterrestrial civilizations should be rather common in the Galaxy.
History
Fermi formulated his paradox in 1950, during a casual conversation in Los Alamos Laboratory with E. Teller and colleagues, with the famous phrase “where are they?” (or “where is everybody?”). His point was that, if there are many extraterrestrial civilizations, Earth should have been visited by one or more of them, long ago and many times over. The discussion went completely unnoticed for many years. The phrase “where are they?” attributed to Fermi but without comments is first encountered in a paper published in 1963 by American astronomer Carl Sagan. Sagan referred to this problem as “Fermi’s paradox” after American astronomer Michael Hart independently rediscovered Fermi’s arguments in 1975.
