I'm a science fiction nut. Ever since I've learned how to read my mind has been wandering to one fantasy place or another. When I was a kid I made up my own world of fantasy and now that I'm an adult I fill them with somewhat more realistic version of what I dreamt of as a kid.
Add in my love of RPGs and an inherent nature to fill the gamer worlds I created with believable life and you can probably begin to understand my obsession with the Drake Equation.
If you don't know what the Drake Equation is then let me explain; it is an evolving mathematic formula used to estimate the approximate number of intelligent communicating civilizations in our galaxy.
You multiply the number of stars in our galaxy by the fraction that have planets, the fraction of those planets that are capable of sustaining life, the fraction of those where life actually develops, the fraction of those where intelligent life develops, the fraction of inteligent life that communicates and the final factor is the length of time the civilization lasts.
At this point in science the entire equation is little more than an educated guess. We're little more than galactic upstarts and know very little about the real numbers the equation represents. After all we only have our sun, our planet Earth, our biology, our race and current civilization to go on. We're largely clueless on what the real numbers are like.
But back to science fiction and RPGs. The Drake Equation is good for another reason. We can guess how many world exist that are habitable and with life on them. It's actually pretty easy, just stop short of the full equation. I came up with nearly 2 and a half billion habitable world in the Milky Way galaxy even when I used rather pessimistic numbers. When I used generally agreed upon accurate numbers I came up with 24 billion habitable worlds to explore.
No matter how you look at it there are a lot of habitable world out there. Too bad NASA canceled the telescope we were going to use to find them. Those 24 billion habitable worlds will have to stay in our science fiction and Role Playing Games.