Fermi Paradox
The contradiction between the high probability of extraterrestrial life and the lack of evidence for it, generating numerous proposed solutions from the Great Filter to the Zoo Hypothesis.
INVESTIGATION OVERVIEW
The Fermi Paradox is the apparent contradiction between the high probability estimates for the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations. The paradox is named after physicist Enrico Fermi, who reportedly asked 'But where is everybody?' during a 1950 conversation about UFOs. The Milky Way galaxy is estimated to contain 100–400 billion stars, many with Earth-like planets. The Drake Equation estimates the number of communicative civilizations. Solutions to the paradox include: the Great Filter (some step in evolution is extremely difficult), the Zoo Hypothesis (ETIs are deliberately avoiding contact), the Dark Forest (civilizations hide to avoid destruction), and the possibility that we are alone.
KEY CLAIMS
The galaxy should be teeming with civilizations, yet we see no evidence
The Great Filter may be ahead of us (we are doomed) or behind us (we are rare)
The Zoo Hypothesis suggests ETIs are observing us without interfering
The Dark Forest theory suggests civilizations hide to avoid destruction
The lack of evidence may be because we haven't looked properly
SUPPORTING EVIDENCE
The Drake Equation estimates N (communicative civilizations) could be in the thousands
Kepler and TESS have confirmed thousands of exoplanets, many in habitable zones
The age of the galaxy (13.6 billion years) allows time for civilizations to spread
No confirmed evidence of extraterrestrial technology has been found
SETI has been searching for 60+ years with no confirmed signal
COUNTER ARGUMENTS
The Drake Equation's variables are highly uncertain; N could be 1 (us)
The galaxy may be too large for civilizations to have reached us
Technological civilizations may be short-lived (self-destruction hypothesis)
We may not recognize ETI signals or technology
The paradox assumes ETIs would want to expand and communicate
TIMELINE
Fermi poses the paradox during a lunch conversation
Drake formulates the Drake Equation
Hart publishes formal analysis of the paradox
Exoplanet discoveries sharpen the paradox
KEY FIGURES
Enrico Fermi
Physicist who posed the paradox
Frank Drake
Astronomer who developed the Drake Equation
Michael Hart
Physicist who formalized the paradox
ORGANIZATIONS
SETI Institute
Research
Breakthrough Listen
Research
SOURCES
RELATED ENTITIES
PEOPLE
Enrico Fermi
Frank Drake
Michael Hart
ORGANIZATIONS
SETI Institute
Breakthrough Listen
EVENTS
Fermi poses the paradox during a lunch conversation
1950
Drake formulates the Drake Equation
1961
Hart publishes formal analysis of the paradox
1975
Exoplanet discoveries sharpen the paradox
2000s–present