Extraterrestrial Intelligence

For many years I have been interested in "what's out there". The television series created by Carl Sagan, Cosmos and the book by the same name opened my eyes to the incredible universe we inhabit. One of the most interesting parts of the book deal with 'The Drake Equation' (also called the Green Bank Equation). Here it is:

The Drake Equation


(from Cosmos by Carl Sagan)

N (sub *) = the number of stars in the Milky Way Galaxy;
f (sub p) = the fraction of stars that have planetary systems;
n (sub e) = the number of planets in a given system that are ecologically suitable for life;
f (sub l) = the fraction of otherwise suitable planets on which life actually arises;
f (sub i) = the fraction of inhabited planets on which an intelligent form of life evolves;
f (sub c) = the fraction of planets inhabited by intelligent beings on which a communicative technical civilization develops;
f (sub L) = the fraction of a planetary lifetime graced by a technical civilization.

Astronomers plug in the appropriate numbers in each of these fractions, and Voila! they come up with "N", the number of extraterrestrial civilizations in the Milky Way Galaxy. That's where we live. (Of course, The Milky Way is only one of ***billions*** of galaxies in the universe.) Unfortunately, some of the numbers are very difficult to assess. For instance,

f (sub i).

We only know of one planet that has evolved intelligence, Earth, and I'm not totally convinced of that yet. . . Anywho, it's fun to play around with this little equation.

By the way, this information was taken directly from Cosmos by Carl Sagan, copyright 1980 by Carl Sagan Productions. Hope you don't mind, Carl. Farewell and goodbye.
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Last update: June 2006 - Missoula, MT