The Drake Equation is designed to estimate the number of Planets possibly having intelligent life forms existing in our Galaxy. But I don't see how it's justified. As far as we know, Earth is the only planet with (intelligent) life forms existing on it, apart from Jupiter's moon Europa and Neptune which have oceans that may or may not contain life. I wonder what Dr Frank Drake set as the criteria to obtain the estimate value. Can I get help with that?
closed as off topic by dmckee♦ May 27 '12 at 14:48
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Well, the mathematical basis for the form of the equation is the rule of product.
Which factors are taken into account can certainly be disputed, i.e. there are certainly more complicated models and more correlations you could come up with. But the Drake equation lists a couple of reasonable yes/no requirements. Certainly, some variables are fairly hard to evaluate quantitatively, which makes it harder to dismiss it as a method for a guess.