* Astronomy

Title: A joint analysis of the Drake equation and the Fermi paradox
Authors: Nikos Prantzos (Institut d'Astrophysique de Paris and Universite P. et M. Curie)

I propose a unified framework for a joint analysis of the Drake equation and the Fermi paradox, which enables a simultaneous, quantitative study of both of them. The analysis is based on a simplified form of the Drake equation and on a fairly simple scheme for the colonization of the Milky Way. It appears that for sufficiently long-lived civilizations, colonization of the Galaxy is the only reasonable option to gain knowledge about other life forms. This argument allows one to define a region in the parameter space of the Drake equation where the Fermi paradox definitely holds (Strong Fermi paradox).

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Compelling evidence suggests we are not alone in universe

Astronomers fiddling with the Drake equation have come up with wildly varying estimates for ET civilizations in our galaxy, from millions to none (Drake himself estimated 100,000). But this month the odds became a bit less rubbery. Working from a miniscule section of the sky, the Kepler Space Observatory has revealed data on 1,235 potential extrasolar planets, with 54 in the life-friendly "Goldilocks Zone" (not too hot, not too cold). There may be up to 50 billion planets in our galaxy alone, astronomers say.
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The famous American astronomer and astrophysicist Carl Sagan explains the Drake equation.
The Drake equation (rarely also called the Green Bank equation or the Sagan equation) is a famous result in the speculative fields of xenobiology, astrosociobiology and the search for extraterrestrial intelligence.

The Drake equation states that:
N = R* x fp x ne x fl x fi x fc x L, where:

N is the number of civilizations in our galaxy, with which we might hope to be able to communicate;

R* is the rate of star formation 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
fl 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.