Jan 26, 2020, 7:53 AM This list appears to omit what is possibly the most important criteria: “Fraction of those planets with a molten iron core, and a moon large enough to keep it molten, so that an electromagnetic shield can protect the atmosphere.” Rate of star formation, R” = 1 solar masses Fraction of stars with planets, fp = 1 Number of habitable planets per star, ne = 4 Fraction of those planets that develop life, fl = 0.25 Fraction of the above that develop intelligent life, fi = 1 Fraction of planets with intelligent life that send signals into space, to = 1 Lifetime of a civilisation that sends signals into space, L = 100
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