Drake equation and planet finding I've just finished reading a Discover mag article on the Drake equation. It suggests that - despite the 45 year difference wherein many terms have been changed or anchored with more precision - the final number is about the same as it always was; there should be about 1 intelligent, radio-capable civilisation within 1000ly of us. The Drake equation: [tex]N = R^*f_pn_ef_lf_if_cL[/tex] where [tex]R^*[/tex] = # of life-friendly stars born each year (~10) [tex]f_p[/tex] = the fraction that have planets (~.9) [tex]n_e[/tex] = the number of habitable planets in the system (~2-3) [tex]f_l[/tex] = the fraction that have life (~.1) [tex]f_i[/tex] = the fraction that have achieved intelligence (~1) [tex]f_c[/tex] = the fraction that have achieved radio (~1) [tex]L[/tex] = the duration of the civilisation (~50,000) But considering the amount of hype in planet finding going on these days, I think we'd be happy finding any kind of life. That would mean we could ignore terms 5 and 6 and drastically incease term 7. Well, since terms 5 and 6 are =1 anyway, they have no effect. I guess it simply boils down to term 7 - how long life exists at all on that planet. Here, it existed for what? 3.5Gy? So, that's 70,000 times longer. I don't know the math they do to get from the final Drake number to a number within 1000ly, but it seems to me that all I have to do is use my multiplying factor. Which means that, according the the Drake equation, there could/should be about 70,000 planets within 1000ly of us that have with some form of (chemically detectable) life. And to boot, this number is significantly more accurate than the traditonal Drake equation, since the margin for error dramatically increases as we move to the right of the equation. Eliminating 2/2 and nailing 1/7 of the right-most terms goes a long way to getting a mroe accurate number. Hm, well, looking even further, it all boils down to term 4: the percent of habitable planets that actually spawn life. That's the big question isn't it? Basically, we can throw the Drake equation away and simply ask what is the likelihood of life on any given habitable planet we find. They say 10%.