by Rod Kennedy

Created on: March 18, 2008

The question of life elsewhere in the universe has occupied mankind's thoughts for hundreds of years. The idea has only grown in the collective consciousness in the years since humans first stepped off this planet. Yet the question of life in the universe, versus that of intelligent life, draws the most heated debate. After all, knowing that there is another planet out there teeming with thousands of species of protozoa is not nearly as intriguing to the mind as knowing if there is life that we might make contact with. However, the question of life elsewhere in the universe is rather academic in light of the sheer size of the universe.

Ironically the question of contact with an alien civilization may have been settled as far back as the 1920's. It was then that astronomer Edwin Hubble first collected data that ultimately led to an approximation of the size and age of the universe. Hubble's measurements allowed astronomers to refine techniques used to measure stellar distances. Those distances turned out to be staggering.

The closest star system to our own, Proxima Centauri, is approximately 4.5 light years away. This seems a relatively small distance until one understands the distance a light year actually represents. The speed of light is 186,000 miles/second. This means that in the course of one year light travels a distance equaling roughly 6 trillion miles; that is a six with 12 zeros after it. A little simple arithmetic tells us that Proxima Centauri is 24 trillion miles away; and this is the closest star. Certainly this form o f notation is too cumbersome for stars further away.

Yet distance does not in any way preclude the possibility of extra solar planets. In the last ten to fifteen years astronomers have discovered over 100 extra solar planets. Many of these are gigantic worlds like Jupiter, but to date our technology is not quite good enough to detect smaller, Earth-like planets. In decades to come it is possible that a means will be found to detect smaller planets. Then the hunt will be on for planets that are not only small enough, but also are at the right distance to support liquid water, a pre-requisite for life as we know it.

If astronomers do discover a distant planet capable of supporting liquid water, what are the odds that that planet will have life? The answer to that question was first proposed by astronomer Frank Drake in 1960. The equation itself is expressed as:

N = R* x f(p) x n(e) x f(l) x f(i) x f(c) x L

In this theoretical equation,

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