Our sun is only a single star in a collection of over
400 billion we call the Milky Way galaxy. The Milky Way is only 1 of
billions of galaxies in the universe. What are the odds that life exists
somewhere in those billions of galaxies. The astronomer Frank Drake
developed a simple equation to estimate the potential number of
communicating civilizations, now called the Drake Equation, that maps out
N = R * f(p) * n(e) * f(l) * f(i) * f(c) * L
"N" here represents the number of
communicating civilizations in our Milky Way galaxy. This number depends
on several factors. "R" is the rate of "suitable" star
formation in the galaxy. "f(p)" is the fraction of stars that
have planets. "n(e)" is the number of these planets around any
star within the suitable ecosphere of the star. An "ecosphere"
is a shell that surrounds a star within which the conditions are suitable
for life to form. Too close and it's too hot; too far and it's too cold.
"f(l)" is the fraction of those planets within the ecosphere on
which life actually evolves. "f(i)" is the fraction of those
planets on which intelligent life evolves. "f(c)" is the
fraction of those planets where intelligent life develops a technology and
attempts communication. The last factor, "L," is the length of
time that an intelligent, communicating civilization lasts.
Making some assumptions about the values for each
variable based on current scientific knowledge and using our own solar
system as the proto-typical standard result in N = L. In other
words, the number of intelligent communicating civilizations in the
galaxy equals the number of years such a civilization lasts! There
should be at least 50 (the number of years WE'VE been around
communicating) and if a communicative civilization lasts for millions of
years, there may possibly be millions of civilizations we can look for.
Not convinced? Plug in your own
and see what result you get.