Concepts
Fermi Paradox
FEHR-mee
Also Known As Hart-Tipler argument
Citation Formats
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The tension between the seemingly high a priori likelihood of extraterrestrial civilizations existing, given the size and age of the universe, and the total absence of observed evidence for them. Traditionally traced to an informal 1950 conversation involving physicist Enrico Fermi, it was not committed to print until a 1963 paper by Carl Sagan, and it has since spawned dozens of competing proposed resolutions.
Facts
Concept Domain Formulated YearTraced to an informal 1950 conversation involving Fermi at Los Alamos; it first appeared in print in a 1963 paper by Carl Sagan. Some historians, including Robert Gray, dispute how much of the modern framing should be credited to Fermi himself. Proposed ByAttribution rests on an informal 1950 lunch conversation at Los Alamos recalled by colleagues; Fermi himself never published on it, and some scientists have questioned how directly the paradox as now framed traces to that conversation. Cross-Tradition Connections
Associated With
Drake Equation, Concepts The Drake equation is the standard attempt to quantify the terms behind the Fermi paradox.
In the Other Atlases
Sources
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationFermi paradox, lead paragraph sectionQuote, Fermi paradox, lead paragraph section
The seeming inconsistency between the lack of evidence of extraterrestrial civilizations and the apparently high likelihood of their existence.
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationFermi paradox, History sectionQuote, Fermi paradox, History section
In 1950, Fermi visited Los Alamos National Laboratory in New Mexico and, while walking to the Fuller Lodge for lunch, casually talked with fellow physicists
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationFermi paradox, Los Alamos conversation sectionQuote, Fermi paradox, Los Alamos conversation section
In 1950, Fermi visited Los Alamos National Laboratory in New Mexico and, while walking to the Fuller Lodge for lunch, casually talked with fellow physicists Emil Konopinski, Edward Teller, and Herbert York about reports of flying saucers and the feasibility of faster-than-light travel.
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationEnrico Fermi, Wikipedia - lead section IPA (respelled to ASCII)Quote, Enrico Fermi, Wikipedia - lead section IPA (respelled to ASCII)
Fermi
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationFermi paradox, Criticism sectionQuote, Fermi paradox, Criticism section
alternative terms like the 'Hart-Tipler argument' or 'Tsiolkovsky-Fermi-Viewing-Hart paradox' have been proposed
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Drake Equation
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Habitable Zone
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Great Filter
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Dyson Sphere
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Von Neumann Probe
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Drake Equation
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Great Filter
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Dyson Sphere
1. Wikipedia (space and spaceflight articles)
Wikimedia FoundationAssociated With: Von Neumann Probe
Open Questions (1 open question)
Why has no evidence of extraterrestrial intelligent civilizations been detected despite the high estimated probability of their existence implied by the size and age of the observable universe?
Every proposed resolution (the Great Filter, limits on interstellar travel and communication, short civilization lifespans, or simply insufficient search effort) remains unconfirmed; no direct evidence distinguishes between them, and SETI searches to date cover only a tiny fraction of the sky, frequency range and time.
What would resolve this A confirmed detection of an extraterrestrial technosignature, or a rigorous, evidence-backed narrowing of the terms in the Drake Equation (especially the odds of abiogenesis, the odds of intelligence evolving, and typical civilization lifetime) would resolve or substantially reframe the question.
Astrobiology and SETIWikipedia (space and spaceflight articles)
Dissenting Readings (1 dissenting reading)
Description
Astrophysicist Milan M. Cirkovic, in 'The Great Silence: The Science and Philosophy of Fermi's Paradox' (2018), argues that many popular framings of the paradox oversimplify the astrobiological, technological and observational uncertainties involved, and that the apparent absence of detected civilizations is far less surprising, and far less paradoxical, once realistic uncertainty in the relevant probabilities and the very limited scope of searches conducted so far are taken into account.
A dissenting reading, from Milan M. CirkovicWikipedia (space and spaceflight articles), Wikimedia Foundation
Frequently Asked Questions
What is the most widely favored solution to the Fermi Paradox?
No consensus; leading candidates include the Great Filter, limits on interstellar travel, and short civilization lifespans.
There is no single solution scientists agree on. Proposed explanations range from the Great Filter, the idea that some step between lifeless chemistry and a detectable spacefaring civilization is extremely rare, to the possibility that interstellar travel and communication are simply harder or slower than imagined, that civilizations tend to be short-lived, or that we have not searched long enough or in the right way to have found anything yet. Some researchers, including Milan Cirkovic, argue the paradox is less paradoxical once realistic uncertainty in the numbers is taken seriously.
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