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Fermi's paradox, extraterrestrial life and the future of humanity: a Bayesian analysis

Published online by Cambridge University Press:  11 January 2016

Vilhelm Verendel*
Department of Energy and Environment, Chalmers University of Technology, 412 96, Gothenburg, Sweden
Olle Häggström
Department of Mathematical Sciences, Chalmers University of Technology, 412 96, Gothenburg, Sweden


The Great Filter interpretation of Fermi's great silence asserts that Npq is not a very large number, where N is the number of potentially life-supporting planets in the observable universe, p is the probability that a randomly chosen such planet develops intelligent life to the level of present-day human civilization, and q is the conditional probability that it then goes on to develop a technological supercivilization visible all over the observable universe. Evidence suggests that N is huge, which implies that pq is very small. Hanson (1998) and Bostrom (2008) have argued that the discovery of extraterrestrial life would point towards p not being small and therefore a very small q, which can be seen as bad news for humanity's prospects of colonizing the universe. Here we investigate whether a Bayesian analysis supports their argument, and the answer turns out to depend critically on the choice of prior distribution.

Research Article
Copyright © Cambridge University Press 2016 

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