Michael Chrichton explains why Drake Equation is NOT SCIENCE
In 1960, Drake organizes the first SETI conference, and came up with the now-famous Drake equation: N=N*fp ne fl fi fc fL
[where N is the number of stars in the Milky Way galaxy; fp is the fraction with planets; ne is the number of planets per star capable of supporting life; fl is the fraction of planets where life evolves; fi is the fraction where intelligent life evolves; and fc is the fraction that communicates; and fL is the fraction of the planet's life during which the communicating civilizations live.]
This serious-looking equation gave SETI a serious footing as a legitimate intellectual inquiry. The problem, of course, is that none of the terms can be known, and most cannot even be estimated. The only way to work the equation is to fill in with guesses. And guesses-just so we’re clear-are merely expressions of prejudice.
Nor can there be “informed guesses.” If you need to state how many planets with life choose to communicate, there is simply no way to make an informed guess. It’s simply prejudice.
Hence, citing the Drake Equation, which amounts to what seems like a logical approach to quantifying a probability that many people want to know, IS NOT EVIDENCE AND NOT SCIENTIFIC for the simple reason that MOST of the factors involved in the equation cannot possibly be known to even 50% confidence...and that is being generous.