One of the fundamental topics in Astrobiology is the study of the distribution of Life in the Universe. The very existence of Life elsewhere is putative – we are, of course, yet to find any solid proof for that. Nevertheless with the power of mathematics, and with our ever-increasing knowledge of the world around us we are able to estimate the probability of the existence of an extraterrestrial civilization with which we would be able to communicate.
Frank Drake’s equation is a wonderful product of thought and is one of the fundamentals of SETI (Search for Extraterrestrial Intelligence). The following is an excerpt from the article on their own website (http://www.seti.org/page.aspx?pid=336)
The equation is usually written:
N = R* • fp • ne • fl • fi • fc • L
N = The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable.
R* =The rate of formation of stars suitable for the development of intelligent life.
fp = The fraction of those stars with planetary systems.
ne = The number of planets, per solar system, with an environment suitable for life.
fl = The fraction of suitable planets on which life actually appears.
fi = The fraction of life bearing planets on which intelligent life emerges.
fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
L = The length of time such civilizations release detectable signals into space.