Estimate the number of intelligent civilizations in our galaxy with the Drake Equation

The Drake equation (also sometimes called the "Green Bank equation," the "Green Bank Formula," or erroneously labeled the "Sagan equation") is a famous result in the fields of exobiology and the search for extraterrestrial intelligence (SETI).

This equation was devised by Dr. Frank Drake (now Professor Emeritus of Astronomy and Astrophysics at the University of California, Santa Cruz) in 1960, in an attempt to estimate the number of extraterrestrial civilizations in the Milky Way (our galaxy) with which we might come into contact. The main purpose of the equation is to allow scientists to quantify the uncertainty of the factors that determine the number of such extraterrestrial civilizations.