Pierre Simon Laplace. Portrait of the French mathematician, astronomer and physicist, Marquis Pierre Simon Laplace (1749-1827). Although from a poor family, Laplace's talent led him to become an assistant of the French chemist Lavoisier. He is better known as a talented mathematician and he used these skills in astronomy. Between 1799 and 1825 Laplace published his most important work, Celestial Mechanics. The book aimed to improve the understanding of the motions in the Solar System by studying the gravitational perturbations between the Sun and the planets. Laplace also proposed that the Solar System was formed from a rotating disk of gas. From an 1833/37 book.