The Drake equation (sometimes called the Green Bank equation or the Green Bank Formula) is an equation used to estimate the potential number of extraterrestrial civilizations in the Milky Way galaxy. It is used in the fields of exobiology and the search for extraterrestrial intelligence (SETI). The equation was devised by Frank Drake in 1962.
The Drake equation states that:
N = R* x fp x ne x fl x fi x fc x L
where:
N = the number of civilizations in our galaxy with which communication might be possible;
and
R* = the average rate of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fℓ = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
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.
Current estimates:
R* = 7/year, fp = 0.5, ne = 2, fl = 0.33, fi = 0.01, fc = 0.01, and L = 10,000 years
NOTE - this is just in our galaxy not the whole of the universe. With the vast numbers involved when we consider the universe it is almost impossible that there is not intelligent life somewhere else in the Universe.
The Drake equation (sometimes called the Green Bank equation or the Green Bank Formula) is an equation used to estimate the potential number of extraterrestrial civilizations in the Milky Way galaxy. It is used in the fields of exobiology and the search for extraterrestrial intelligence (SETI). The equation was devised by Frank Drake in 1962.
The Drake equation states that:
N = R* x fp x ne x fl x fi x fc x L
where:
N = the number of civilizations in our galaxy with which communication might be possible;
and
R* = the average rate of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fℓ = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
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.
Current estimates:
R* = 7/year, fp = 0.5, ne = 2, fl = 0.33, fi = 0.01, fc = 0.01, and L = 10,000 years
N = 7 × 0.5 × 2 × 0.33 × 0.01 × 0.01 × 10,000 = 2.31
So two communicative civilizations exist in our galaxy at any given time, on average, plus two hundred more that are not trying to communicate.
http://en.wikipedia.org/wiki/Drake_equation
NOTE - this is just in our galaxy not the whole of the universe. With the vast numbers involved when we consider the universe it is almost impossible that there is not intelligent life somewhere else in the Universe.