Drake equation - Wikipedia, the free encyclopedia
where:
N is the number of civilizations in our galaxy with which communication might be possible;
and
R* is the average rate of star formation per year in our galaxy
fp is the fraction of those stars that have planets
ne is the average number of planets that can potentially support life per star that has planets
f***8467; is the fraction of the above that actually go on to develop life at some point
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L is the length of time such civilizations release detectable signals into space.