Fermi paradox

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Fermi paradox
Enrico Fermi , Italian-American physicist, received the 1938 Nobel Prize in physics for identifying new elements and discovering nuclear reactions by…
Enrico Fermi , Italian-American physicist, received the 1938 Nobel Prize in physics for identifying new elements and discovering nuclear reactions by… Photo: Department of Energy-Office of Public Affairs, restored by Yann · Public domain · via Wikimedia Commons
TypeTerm
Also known asWhere is everybody

The Fermi paradox is the apparent contradiction between the high likelihood that intelligent life exists elsewhere in the galaxy and the lack of any clear evidence of it. It is named after physicist Enrico Fermi, whose question "Where is everybody?" arose from a 1950 lunchtime conversation about flying saucers.[1]

Origin

Edward Teller , in 1958, as Director of Lawrence Livermore National Laboratory. Note that the picture at his top left is of the UC Radiation…
Edward Teller , in 1958, as Director of Lawrence Livermore National Laboratory. Note that the picture at his top left is of the UC Radiation… Photo: Lawrence Livermore National Laboratory, restored by w:User:Greg L , Papa Lima Whiskey · CC BY-SA 3.0 · via Wikimedia Commons

In 1950 at Los Alamos, Fermi was walking to lunch with Emil Konopinski, Edward Teller and Herbert York, talking about recent flying saucer reports and whether faster-than-light travel was possible. After the talk had moved on, Fermi suddenly asked where everybody was. York recalled that Fermi then calculated that Earth should have been visited long ago and many times over; Teller remembered only a remark that the distances might be very great.[1]

Fermi never published on the subject, and some scientists argue the idea has been misattributed. Carl Sagan first mentioned it in print in 1963, and in 1975 Michael Hart published a detailed study concluding that humans are probably the first civilisation in the galaxy. Hart grouped possible answers into four kinds: travel is impossible, aliens choose not to visit, they have not had time, or they have already come.[1]

Proposed answers

This image of Earth’s city lights was created with data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS)…
This image of Earth’s city lights was created with data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS)… Photo: Data: Marc Imhoff/NASA GSFC, Christopher Elvidge/NOAA NGDC; Image: Craig Mayhew and… · Public domain · via Wikimedia Commons

Explanations fall into several broad groups:[1]

  • Rarity. Life, or intelligent life, may be extremely rare. The "Great Filter", proposed by Robin Hanson in 1996, is some step, such as the origin of life, that very few worlds get past.
  • Short lifetimes. Civilisations may destroy themselves, or may only send out detectable signals for a short time.
  • Choice. Aliens may choose not to expand, or deliberately leave Earth alone. As early as the 1930s the Russian rocket pioneer Konstantin Tsiolkovsky suggested that humanity is kept in quarantine to allow its culture to develop.

Relevance to UFOs

Illustration of official papers and files
Illustration: official papers and files. An artist's impression drawn for this site, not a photograph of the event.

Hart's fourth possibility, that extraterrestrials have already visited, is where the paradox overlaps with claims about UFOs; Fermi's question itself began with a conversation about flying saucer reports. The paradox also had political effects: in 1981 Senator William Proxmire cited it when he helped end NASA's funded search for extraterrestrial intelligence.[1]

References

This page was last edited on 31 October 2026. Articles are written in our own words from the sources listed under References; disputed claims are attributed to the people who made them.

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