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Drake Equation

(estimate of advanced life in the Milky Way)

The Drake Equation is a well-known example of a model to estimate the number of detectable extraterrestrial advanced civilizations in the Galaxy. It was formulated by astronomer Frank Drake in 1961. The equation:

N = R* × fp × ne × fl × fi × fc × L


  • R* is the average rate of Star Formation in the galaxy
  • fp is the fraction of those stars with planets
  • ne average number of life-supportable planets in such systems, i.e., in the Habitable Zone and so forth
  • fl fraction of those that actively develop life
  • fi fraction of those that develop intelligent life
  • fc fraction of those that develop technology that can release detectable signals
  • L - length of time for which such systems release detectable signals