[bwolf]

Originally Posted by ninty9

Their unknown yes, but they can be estimated. And whatever the estiates are the equation still simply states that there is probably a good chance that we are not alone. Therefore the equation is still a valid tool in the scientific cuommunity.

But our estimates of things like "fraction of planets in ne where life evolves" are pretty much shots in the dark... we could just as easily simply guess the number of communicating civilizations in the galaxy. Also, I don't think this equation is used too often in the serious scientific community... you can find a info about it on a bunch UFO sites and high-school-student-made-looking sites, but if you go to serous physics sites, astrology, astrophysics, cosmology, you'll see it isn't used much because we only know values of a few variables and a few, most especially the duration of the civilization... we have absolutely no idea.