Drake equation
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The Drake equation is a formula written by radio astronomer Frank Drake in 1961 to estimate the number of civilisations in the Milky Way that might be detectable by radio. It was intended as an agenda for discussion, not a precise calculation, and most of its terms remain highly uncertain.[1]
The equation
The equation multiplies seven factors:[1]
- the rate at which stars form in the galaxy;
- the fraction of stars with planets;
- the number of planets per system that could support life;
- the fraction of those on which life appears;
- the fraction of those on which intelligence develops;
- the fraction of civilisations that give off detectable signals;
- the length of time they keep doing so.
History
In 1959 physicists Giuseppe Cocconi and Philip Morrison suggested in Nature that radio telescopes could detect signals from other civilisations. In 1960 Drake carried out Project Ozma, listening to two nearby Sun-like stars from the National Radio Astronomy Observatory at Green Bank, West Virginia; no signals were found.[1] He then hosted the first scientific meeting on the search for extraterrestrial intelligence (SETI) at Green Bank in 1961, writing the equation as the meeting's agenda. The ten participants, including Carl Sagan, called themselves "The Order of the Dolphin".[1]
Estimates
The 1961 group's guesses gave between about 20 and 50 million civilisations, and they concluded that the number was roughly equal to the average lifetime of a communicating civilisation in years. Later writers using more pessimistic values have produced answers of less than one.[1][2] Critics point out that because several factors are pure guesses, the equation cannot give a firm answer.[1]
References
- Drake equation — Wikipedia · en.wikipedia.org · archived copy
- Fermi paradox — Wikipedia · en.wikipedia.org · archived copy
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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