1. The Drake equation is a probabilistic argument used to arrive at an estimate of the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.
  2. It was written in 1961 by Frank Drake as a way to stimulate scientific dialogue at a meeting on the search for extraterrestrial intelligence (SETI).
  3. This is the equation
  4. N = The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable
  5. R* = The rate of formation of stars suitable for the development of intelligent life
  6. fp = The fraction of those stars with planetary systems
  7. ne = The number of planets, per solar system, with an environment suitable for life
  8. fl = The fraction of suitable planets on which life actually appears
  9. fi = The fraction of life bearing planets on which intelligent life emerges
  10. fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space
  11. L = The length of time such civilizations release detectable signals into space