The Fermi Paradox, named after the Italian-American physicist Enrico Fermi, is a contradiction between the lack of evidence for extraterrestrial civilizations elsewhere in the Milkyway galaxy and various high estimates for their probability. In outline, the argument for extraterrestrial life runs as follows:
- The Milky Way comprises hundreds of billions of stars and billions of them are similar to the sun.
- It is highly probable that some of these stars will have planets like Earth.
- Via the Copernican principle if we assume that Earth is not particularly special, then the intelligent life should also exist on some fraction of these Earth-like planets.
- There are chances that some of these intelligent life-forms might develop advanced technology and even interstellar travel.
- Interstellar travel would take a long time, but as they are many sun-like stars that are billion years older, there has been plenty of time for such travel to have occurred.
- Given all this, why haven’t we met any trace of aliens? Where is everybody?