As important as the question of what we will do is, we should think about how likely finding extraterrestrial intelligence is. One man has done just that - Dr. Frank Drake, the President of the SETI Institute. While working as a radio astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, Dr. Drake thought up a way to estimate the number of technological civilizations that might exist among the stars.

R_* equals the rate of formation of suitable stars, or more specifically, the rate of formation of stars with a large enough "habitable zone" and long enough lifetime to be suitable for the development of intelligent life.

f_p equals the fraction of those stars with planets. The fraction of Sun-like stars with planets is currently unknown, but evidence indicates that planetary systems may be common for stars like the Sun.

n_e equals the number of "earths" per planetary system. All stars have a habitable zone where a planet would be able to maintain a temperature that would allow liquid water. A planet in the habitable zone could have the basic conditions for life as we know it.

f_l equals the fraction of those planets where life develops. Although a planet orbits in the habitable zone of a suitable star, other factors are necessary for life to arise. Thus, only a fraction of suitable planets will actually develop life.

f_c equals the fraction of planets where technology develops. This is the fraction of planets with intelligent life that develop technological civilizations, i.e., technology that releases detectable signs of their existence into space.

L equals the "Lifetime" of communicating civilizations or the length of time such civilizations release detectable signals into space.

Let’s run an example of the equation. Let’s set R_* at 100 billion, about the number of stars in the Milky Way Galaxy. With f_p we’ll "generously" say 1 star in 10,000 forms planets, which considering the number of extra solar planets discovered in our neighborhood is probably way too high. Next, we’ll say only 1 star in 1,000 with planets has planets in the habitable zone, hence n_e is .001. Now we’ll say 1 planet in 1,000 in the habitable zone forms life, so f_l also = .001, although experiments with creating the basic building blocks of life suggest this could be much lower. We’ll say that with enough time (like 4.5 billion years) life will always develop intelligence, therefore f_i is 1. Likewise, generously we’ll assume that intelligence always leads to technology, f_c is also 1. Lastly, we’ll use ourselves for the lifetime number. We’ve been broadcasting signals for 60 years and there are no indications we’ll stop in the next 40 (but after that I won’t speculate), so we’ll set L at 100. What does the Drake equation say? Under this example, there are no less than 1,000 intelligent civilizations in our galaxy alone! Now multiply this by 100 trillion galaxies in the universe....