The Drake equation is a lot like the Fermi paradox. They are not revelations of some truth about the nature of intelligent life in the Universe (or even our galaxy), they are merely reflections of our utter ignorance of the subject.
Where do these figures come from? For fully 5 out of the 7 parameters to the Drake equation we have extraordinarily limited data. How common are Earth-like planets? Call back in about 5-10 years when we'll have some solid data from the Kepler mission. How common is life on Earth-like planets? Who knows? We aren't even close to being able to get solid figures on that. If we can find life on Mars or rule life out of ever having existed there then we'll have a teeny tiny bit of data. But even then such an estimate will be biased by the anthropic principle and at best only accurate to perhaps a single order of magnitude (if that). Even then that leaves half of the parameters as wild ass guesses.
Not to mention that the parameters aren't independent. If we find life on Mars existed or still exists that would make f-sub-l higher, but it would probably make f-sub-i correspondingly lower.
Worse yet, the very premise of the Drake equation is at odds with the premise behind the Fermi paradox. If even a single, slow colonizing intelligent civilization ever existed in our galaxy it would make the number of possible communicative worlds differ by perhaps even 6 or 9 orders of magnitude.
The exercise is only worthwhile when it is not taken seriously, which is a bit of a catch-22.
Where do these figures come from? For fully 5 out of the 7 parameters to the Drake equation we have extraordinarily limited data. How common are Earth-like planets? Call back in about 5-10 years when we'll have some solid data from the Kepler mission. How common is life on Earth-like planets? Who knows? We aren't even close to being able to get solid figures on that. If we can find life on Mars or rule life out of ever having existed there then we'll have a teeny tiny bit of data. But even then such an estimate will be biased by the anthropic principle and at best only accurate to perhaps a single order of magnitude (if that). Even then that leaves half of the parameters as wild ass guesses.
Not to mention that the parameters aren't independent. If we find life on Mars existed or still exists that would make f-sub-l higher, but it would probably make f-sub-i correspondingly lower.
Worse yet, the very premise of the Drake equation is at odds with the premise behind the Fermi paradox. If even a single, slow colonizing intelligent civilization ever existed in our galaxy it would make the number of possible communicative worlds differ by perhaps even 6 or 9 orders of magnitude.
The exercise is only worthwhile when it is not taken seriously, which is a bit of a catch-22.