From the SETI notebook of James Brown Drakes Equation One of the first things asked when I say that I am evolved in the search for extraterrestrial life is "what makes you think there is any one else in the universe ?". That's a very good question and one that deserves an answer. It is also one that has not been successfully answered over the whole of human experience. Carl Sagan participated in a conference of people interested in the question of Communication with Extraterrestrial Intelligence (CETI) that was held in the USSR back in 1971. In his introduction address he said something that gets the whole thing in perspective. He said "..the cetaceans (whales) are undoubtedly another intelligent species inhabiting our planet, and it has been argued that if we cannot communicate with them we should not be able to communicate with extraterrestrial civilizations". Without much reflection it would seem that it should be much easier to communicate with whales than ET's. After all we share the same planet, both breath oxygen, eat plants that depend on the sun for there energy source. But since that meeting, 15 years ago, we are no closer to talking with whales than we ever were. The conference had as its agenda the task of estimating the possibility of communication with extraterrestrial intelligence and since they were all capable scientific people they felt it necessary to express there doubts and optimism in the form of mathematics. Dr. Frank Drake was at the same conference and had sometime earlier created a mathematical expression of the possibility that could be used as a framework for this and future discussions. Drakes equation became a way for experts to tackle the problem piecemeal, concentration in there own specialty without trying to understand the question as a whole. For example the evolution of technical civilizations was taken by an anthropologist, the rate of star formation in the universe by a cosmologist, etc. The equation is: N = R Fp Ne F1 Fi Fc L Where: N = Number of civilizations to look for R = Rate of star formation Fp= Fraction of stars with planetary systems Ne= Ecologically suitable planets. F1= Fraction of planets on which life occurs. Fi= Fraction of planets with life AND intelligent life Fc= Fraction with communication capabilities like ours L = Life time of such a civilization It was generally agreed on that the terms most easily estimated were the rate of star formation and the number of stars with planets. The most difficult term was "L" the life time of an intelligent civilization because we only have experience with one such civilization and it appears intent on terminating itself at the earliest possible moment. AS you would expect none of these things can be estimated with anymore than a good guess but here is what the results seem to be based on everything we now know about the problem. An optimist, like Dr Sagan would say that there is at least 300,000 civilizations that are capable of sending signals and that we could detect in our galaxy alone. A pessimist, and there were several even in that conference, would say that there can be as few as 100 possible civilizations down to and including zero. So what is the true number of civilizations? We shall never know because even when we find the first, we shall never know when we have found the last. So what is the true number of civilizations? X-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-X Another file downloaded from: NIRVANAnet(tm) & the Temple of the Screaming Electron Jeff Hunter 510-935-5845 Rat Head Ratsnatcher 510-524-3649 Burn This Flag Zardoz 408-363-9766 realitycheck Poindexter Fortran 415-567-7043 Lies Unlimited Mick Freen 415-583-4102 Specializing in conversations, obscure information, high explosives, arcane knowledge, political extremism, diversive sexuality, insane speculation, and wild rumours. ALL-TEXT BBS SYSTEMS. Full access for first-time callers. We don't want to know who you are, where you live, or what your phone number is. We are not Big Brother. "Raw Data for Raw Nerves" X-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-X