La·place \lȧ-plȧs\ Pierre–Simon (1749–1827), French astronomer and mathematician. Laplace has often been called the Newton of France. He successfully applied the Newtonian theory of gravitation to the solar system by accounting for all of the observed deviations of the planets from their theoretical orbits. By 1786 he was able to prove that the eccentricities and inclinations of planetary orbits to each other will always remain small, constant, and self-correcting. He also investigated tides, specific heats, capillary action, electricity, and the equilibrium of a rotating fluid mass. By demonstrating that the attractive force of a mass upon a particle (regardless of direction) could be obtained directly by differentiating a single function, he established the mathematical basis for the scientific study of heat, magnetism, and electricity.