French mathematician, astronomer, and physicist Marquis Pierre-Simon de Laplace (1749–1827) was one of the first to work out the gravitational mechanics of the solar system using mathematics. In his *Mécanique Céleste (Celestial Mechanics),* Laplace translated the geometrical study of mechanics used by Isaac Newton to one based on calculus (or physical mechanics). He also proved the stability of the solar system, but only on a short time scale. Laplace is also known for his theory about the formation of the planets. He believed they originated from the same primitive mass of material, a theory now known as Laplace’s nebular hypothesis. His other studies included major contributions to differential equations and to the theory of probability.