"The Drake Equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy."
The Drake Equation on Behance
BBC - Future - Science Environment - Drake equation How many alien civilizations exist -152752
[astrobiology] The famous Drake Equation put forward by Frank Drake back in the 1961. See also "Rare Earth equation" (a somewhat less trusted equation, but interesting nonetheless). ~Al. A.
The Drake Equation poster on Behance
Drake equation - probabilistic argument to estimate the number of alien civilizations in the galaxy
Fans of the Drake Equation can rejoice, because NASA just announced that the Kepler spacecraft has discovered 1,284 new planets, 9 of them could support life...