<P> The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy . </P> <P> The equation was written in 1961 by Frank Drake, not for purposes of quantifying the number of civilizations, but as a way to stimulate scientific dialogue at the first scientific meeting on the search for extraterrestrial intelligence (SETI). The equation summarizes the main concepts which scientists must contemplate when considering the question of other radio - communicative life . It is more properly thought of as a Fermi problem rather than as a serious attempt to nail down a precise number . </P>

The drake equation is used to predict the number of