Britannica
Sources used in this answer
Why is the lack of confirmed alien visits part of the Fermi paradox?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
extraterrestrial intelligence
An artist's conception depicts Kepler-186f, the first Earth-sized extrasolar planet found in its star's habitable zone.
The Fermi paradox highlights a contradiction between the high statistical probability of extraterrestrial intelligence and the total lack of evidence for its existence. The lack of confirmed alien visits is central to this paradox because, given the age and size of the Milky Way Galaxy, it is mathematically plausible that an advanced civilization could have explored or colonized the entire galaxy many times over in Earth's history.12
Physicist Enrico Fermi famously questioned, "Where is everybody?" because, assuming even modest interstellar travel speeds, the galaxy should have been traversed long ago. The absence of such contact suggests several possibilities:12
- Technological or Biological Limits: Interstellar travel may be impossible, or civilizations may not last long enough to achieve it.12
- The Great Filter: An evolutionary or technological "wall" may prevent life from reaching the stage of galactic expansion.12
- Intentional Silence: Advanced civilizations may choose not to communicate or may avoid revealing their location to potential predators.2
- Human Limitations: We may simply lack the technology or understanding to detect signals that are already present.2