The Drake Equation
It is conventional practice in
the SETI community to parse this imposing number of possible sites for life by
application of the Drake Equation.
First proposed by Frank Drake in 1961, this simple formula sets out the
factors that determine the number of contemporary broadcasting societies in our
own galaxy (this latter limitation is mere parochialism. One could easily consider the rest of the
universe, but signals from far-away galaxies are clearly more difficult to
detect.) The Drake Equation estimates
the number of suitable stars, multiplies this by the fraction with habitable
planets, then by the fraction of those planets that have developed
technologically sophisticated life. The
resulting product is then multiplied by the fraction of the galaxy’s lifetime
during which such a technologically civilization is active (this incorporates
the famous “L” term, which is the lifetime of a technological
civilization).
While a reasonable approach,
the Drake Equation makes the assumption that “they” are like “us”: evolved
upon, and living on (or near) a biologically suitable planet. This is also the assumption made by both
Hollywood and by my esteemed opponent.
Contributed by: Dr. Seth Shostak
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