The Drake Equation

As far as completely useless equations go, my favorite is probably the Drake Equation. This may or may not be because it's the only completely useless equation that I know. It's kind of neat, anyway. Basically, the Drake Equation (thought up by Frank Drake--he's got two first names--in 1961) is to calculate the number of detectable aliens in the universe. It goes something like:

Where 

N = number of alien civilizations

R* = avg. rate of star formation

f_P = fraction of stars with planets

n_e = avg number of life-supporting planets per star

f_l = fraction of potentially life-supporting planets that actually develop life

f_i = fraction of f_l  that actually develop into intelligent life forms.

f_c = fraction of f_i that develop technology that make it easier for us to find them

L = length of time that civilizations have had above technology

So why is it useless? Because almost all of the above are unknowns. We can get a pretty decent number for average star formation, and even for fraction of stars with planets, but the rest? So far, the only criterion for life we have is water. How many planets have water? No one actually knows. It just gets more questionable from there.

Essentially, you can turn N into whatever number you want, depending on how optimistic you're feeling that day. It's a kind of neat idea, sure. But does it actually give us any sort of useful information at all? Nope. None, whatsoever. But who cares. Because aliens. And Frank Drake is just a pretty cool name.

References:

Drake Equation: Wikipedia.org

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