What's the chance of life beyond Earth?

If science fiction authors and Star Trek writers can envision life as we don't know it ... then surely the Universe is equally creative.

- Michael Lemonick

It was recently estimated that there are 70 thousand million million million observable stars in the universe, not to mention those that are beyond our detection. Given this, it is my personal belief is that we are not alone in the universe. There's no real science behind this belief, but to me the size and numbers involved seem to indicate that there is more than a fair chance that there is life, intelligent or otherwise, somewhere out there. Otherwise, it would be an incredible waste of space.


Frank Drake and his famous equation.
There are, of course, many people who are more scientific in their approach to determining the existence of life beyond earth than I am. One such person is Frank Drake. Currently Chairman of the Board of the SETI Institute, in 1961 he developed the now famous Drake equation, which for the first time attempted to quantify the probability of detecting life (in this case, intelligent life) beyond Earth.


The Drake equation basically states that the number of civilizations we could detect will depend on the rate at which stars like our sun form, then the fraction of these stars that form planets, then the number of these planets that are hospitable to life, then the number of these planets where life actually emerges, then the number of these planets were life evolves to develop intelligence, then the fraction of these planets where interstellar communication evolves and, finally, the time that communication is carried on for before these intelligent civilizations die out or stop trying. More succinctly, the equation looks like:

The Drake equation - N=R*FpNeFlFiFcL
Where:
N the number of detectable civilizations
R* the rate at which Sun-like stars form
Fp the fraction of stars that form planets
Ne the number of planets per solar system hospitable to life
Fl the fraction of planets where life emerges
Fi the fraction of life bearing planets where intelligence evolves
Fc the fraction of such planets where the inhabitants develop interstellar communication
L the length of time such civilizations continue to communicate before they end


Not only does the Drake equation convert the question of the existence of extraterrestrial neighbours from one of metaphysics to hard science, but it gives those looking for life beyond Earth a place to start.