Fermi's paradox, Extraterrestrial Life and the Future of Humanity: a Bayesian Analysis
Journal article, 2017

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.

Bayesian analysis

Fermi paradox

great filter


extraterrestrial life


Vilhelm Verendel

Chalmers, Energy and Environment, Physical Resource Theory

Olle Häggström

Chalmers, Mathematical Sciences, Applied Mathematics and Statistics

University of Gothenburg

International Journal of Astrobiology

1473-5504 (ISSN)

Vol. 16 1 14-18

Driving Forces

Sustainable development

Subject Categories

Astronomy, Astrophysics and Cosmology

Probability Theory and Statistics


Basic sciences



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