Probability 1: Why There Must Be Intelligent Life in the Universe Aczel, A.D. 1998
In a universe infinitely large, what is the probability of intelligent life on another planet? Sounds like a trick question, but for anyone versed in cosmology and statistics, the answer is 1; that is, there must be life on at least one other planet in the universe. This is Amir Aczel’s theorem. But, as physicist Enrico Fermi once asked, if that’s true, where is everyone? Aczel tackles that paradox after he goes through the statistical calculations for the probability of intelligent life, considering factors such as how many stars are in a galaxy, how many of those stars might be hospitable, how many might have planets, and how many planets might have environments suitable to support life as we know it (or as we don’t). Aczel also provides an overview of the relevant developments in astronomy and biology—laying the groundwork to show that the universe’s chemistry must add up to life. Whether life was spread through the universe by chunks of debris like ALH84001—the enigmatic meteorite from Mars that contained tantalizing hints of the possibility of life—or arose independently, Aczel is sure it is out there. After teasing readers with scientific history, Probability 1 delivers on its promise to prove Aczel’s conjecture through a clearly explained application of known statistical theory to the chaos of the universe.—Therese Littleton

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