A way of estimating the number of intelligent, technological species in existence in our Galaxy.
N = the number of species described above at any given moment in our Galaxy
R = the rate of star formation in our Galaxy [stars per year] = 10 for our Galaxy
fp = the fraction of stars which have planets
ne = the number of habitable planets per system with planets
fl = the fraction of habitable planets upon which life arises
fi = the fraction of these planets upon which life develops intelligence
ft = the fraction of these planets where the intelligence develops into a technological civilization capable of communication
L = the mean lifetime of such a technological civilization [years]
- Seti Institute - Drake Equation What do we need to know about to discover life in space?