The unexplained parameters are the factors of the Drake equation: The number of civilizations, N, is assumed to be equal to the mathematical product of - th

The unexplained parameters are the factors of the Drake equation: The number of civilizations, N, is assumed to be equal to the mathematical product of - the average rate of star formation, R∗, in our galaxy, - the fraction of formed stars, *fp*, that have planets, - for stars that have planets, the average number of planets *ne* that can potentially support life, - the fraction of those planets, *fl*, that actually develop life, - the fraction of planets bearing life on which intelligent, civilized life, *fi*, has developed, - the fraction of these civilizations that have developed communications, *fc*, i.e., technologies that release detectable signs into space, and - the length of time, *L*, over which such civilizations release detectable signals. https://en.wikipedia.org/wiki/Drake_equation https://en.wikipedia.org/wiki/Drake_equation