The Fermi Paradox
What this means
Serious people have done real work and there is real evidence for the idea, but it falls short of proof. We show what supports it, what is missing and who disagrees.
If the galaxy is old and full of planets, why have we found no sign of anyone else?
The question is named for the physicist Enrico Fermi, who is reported to have asked over lunch at Los Alamos in 1950, "Where is everybody?" The idea is that a galaxy billions of years old should have been crossed by any technological species many times over, yet we see no confirmed sign of one.
Many answers have been proposed. Intelligent life may be extremely rare; a "Great Filter," a point life rarely passes, may lie behind or ahead of us; civilizations may not last; or we may simply not be looking in the right way. Robin Hanson named the Great Filter in a 1998 essay. In 2018 Sandberg, Drexler and Ord argued that with realistic uncertainty about the factors in the Drake equation, an empty galaxy is not surprising.
None of these answers has direct evidence. The paradox itself is well documented as a question; the explanations are hypotheses, which is why the page sits at Almost credible and not higher.
One 2018 study from Oxford's Future of Humanity Institute found that, given honest uncertainty, there is a substantial chance we are alone in the galaxy.
Some scientists argue the paradox is not a paradox at all, because we have searched only a tiny fraction of the possibilities.
