### Drake equation

(estimate of advanced life in the Milky Way)

The **Drake equation** is a well-known example of a
model relating the number of detectable extraterrestrial
advanced civilizations in the galaxy to quantities
with the potential for determination or some degree of estimation.
The resulting number of interest in
the field of SETI (**search for extraterrestrial intelligence**).
The equation was formulated by astronomer Frank Drake in 1961.

*N = R*_{*} × f_{p} × n_{e} × f_{l} × f_{i} × f_{c} × L

where:

- N - the resulting number.
- R
_{*} - average rate of star formation in the galaxy.
- f
_{p} - average fraction of those stars with planets.
- n
_{e} - average number of life-supportable planets in such systems, i.e., in the habitable zone and so forth.
- f
_{l} - fraction of those that actively develop life.
- f
_{i} - fraction of those that develop intelligent life.
- f
_{c} - fraction of those that develop technology that can release detectable signals.
- L - length of time for which such systems release detectable signals.

(*equation,exoplanets,life,astrobiology*)
**Further reading:**

http://en.wikipedia.org/wiki/Drake_equation

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