Laplace, Pierre Simon

French astronomer and mathematician. In 1796 he theorized that the Solar System originated from a cloud of gas (the nebular hypothesis). He studied the motion of the Moon and planets, and published a five-volume survey of celestial mechanics, Traité de méchanique céleste (1799–1825). Among his mathematical achievements was the development of probability theory.

Traité de mécanique céleste contained the law of universal attraction – the law of gravity as applied to the Earth – and explanations of such phenomena as the ebb and flow of tides and the precession of the equinoxes. He became Marquis in 1817.