Siméon-Denis Poisson (1781-1840), French mathematician and physicist, born in Pithiviers. He is best known for his contributions to theories of electricity and magnetism. Poisson also published extensively on other topics, such as the calculus of variations, differential geometry, and probability theory. The “Poisson distribution” is a special case of the binomial distribution in statistics.

Poisson studied at the École Polytechnique in Palaiseau and was strongly influenced by the French mathematicians Joseph Louis Lagrange and Pierre Simon Laplace. In 1802 Poisson became the assistant of French mathematician Jean Baptiste Fourier, whose Chair he assumed in 1808. Later Poisson became the first professor of mechanics at the Sorbonne and a leading member of the French scientific establishment. In his work on electricity that was published in 1812, he adopted the same two-fluid model of electricity that French physicist Charles Augustin Coulomb had used before him: like fluids repelled and unlike attracted, according to the inverse-square law. A body became electrified either positively or negatively when the uniform distribution of both fluids was disturbed. He used Lagrange's potential function to mathematically formulate the distribution of electric charges on the surface of conductors. This work was important in the eventual development of the theory of absolute measurement, and such concepts as electrical potential. In 1824, Poisson demonstrated that these formulations were equally applicable to magnetism. In astronomy he worked on the mathematics of the motion of the moon and the dependence of the force of gravity on the distribution of mass within a planet. Poisson also studied the theory of elasticity.