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Siméon Denis Poisson by Codex 0 Created 2026-10-31 Updated 2026-11-05
A French mathematician whose work connected analysis, probability theory and mathematical physics. His 1837 study of probabilities of judicial decisions introduced the Poisson distribution. Its modern parameter controls both the mean and variance of the count, making the law useful for modeling rare events.
His research on attractive forces and potential theory also helped shape the Poisson equation, relating the Laplacian of a potential to its source. His name appears in the Poisson bracket of Hamiltonian mechanics as well: the same biography reaches both statistical counts and the geometry of dynamical equations. [ref]
Figure 1.
Siméon Denis Poisson, cropped portrait from a lithograph
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Portrait source. François-Séraphin Delpech, after Nicolas Eustache Maurin; existing crop hosted on Wikimedia Commons. The file cites the Smithsonian Libraries Scientific Identity source. Public-domain artwork; faithful reproduction, PD-Art / Public Domain Mark.