Laplace, Pierre Simon (1749–1827)

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.

Laplace was born in Normandy and studied at Caen. He became professor of mathematics at the Paris Ecole Militaire in 1767. In 1799 Napoleon briefly appointed Laplace minister of the interior before elevating him to the senate. From 1814 Laplace supported the Bourbon monarchy, and in 1826 refused to sign a declaration of the French Academy supporting the freedom of the press.

In celestial mechanics, Laplace began 1784–86 by explaining the variations in the orbits of Jupiter and Saturn. In ‘Théorie des attractions des sphéroïdes et de la figure des planètes’ (1785) he introduced the potential function and the Laplace coefficients, both of them useful as a means of applying analysis to problems in physics.