The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way Galaxy.

Frank Drake began as a radio astronomer, studying the planets of our System. He went on for the search for extraterrestrial intelligence (SETI), then the Project Ozma in 1960, an attempt at extraterrestrial communications.

UFOdB.com believes that its important to understand the possibilities of extra-terrestrial life around our planet earth.

The other aspect to keep in mind is the amount of life with a considerable level of intelligence for which the drake equation take in consideration.

N = number of civilizations with which humans could communicate

R_* = mean rate of star formation

f_P = fraction of stars that have planets.

n_e = mean number of planets that could support life per star with planets.

f_l = fraction of life-supporting planets that develop life.

f_i = fraction of planets with life where life develops intelligence.

f_c = fraction of intelligent civilizations that develop communication.

L = mean length of time that civilizations can communicate.