Simeon Denis Poisson (1781-1840), French mathematical physicist. Poisson was born at Pithiviers and educated at Paris in the Ecole Polytechnique. His first mathematical papers were published before he graduated. His work in electricity and magnetism formed the basis of mathematical physics. Poisson developed equations for use in electrostatics, particularly with regard to the force exerted by the charge on the surface of a conductor and the distribution of charge on a sphere. He also worked on theories of heat and elasticity. Studying probability theory, Poisson developed the binomial distribution that is named after him. He also made major contributions to celestial mechanics by extending the work of Lagrange on the stability of planetary orbits.