French mathematician and astronomer, also known as Marquis de Laplace (1806 - 1817) or Compte de Laplace, b. 23 March 1749 (Beaumont-en-Auge, Normandy, France), d. 5 March 1827 (Paris).
Laplace was the son of a peasant farmer. He showed mathematical ability during his time at the military academy in Beaumont and moved to Paris to embark on a mathematical career when he was 18. Having submitted an example of his ability (a discourse on principles of mechanics) to the mathematician Jean d'Alembert he was recommended for a professorship at the École Militaire.
The theme of Laplace's work throughout his illustrious career was the application of Newton's law of gravitation to the solar system. The interactions between the various planets and the sun itself are quite complicated and lead to astonishing effects, such as an apparent shrinking or expansion of orbits. Laplace showed in 1773 that these effects were the result of eccentricities and inclinations of orbits and therefore periodic; in other words, the solar system is in a stable configuration. In 1786 he showed that these eccentricities and inclinations will always be small and self-correcting.
In 1796 Laplace published a popular treatise on celestial mechanics, still regarded as a model of French prose, Exposition du système du monde (Explanation of the System of the World). This was followed in 1814 by a book in even more popular style, Essaie philosophique sur les probabilités (Philosphical Essay on Probability). During the same time he published his main scientific work Traité de mécanique céleste (Celestial Mechanics) in five volumes between 1798 and 1827.
In mathematics Laplace's name is remembered through the Laplace transform, an integral transformation useful for solving boundary value problems, and through the Laplace equation, a second order differential equation. He expressed his admiration for the unknown inventors of the position value number system.
During the French Revolution Laplace was president of the board of longitude and assisted in the organization of the metric system.
Whitrow, G. J. (1995) Pierre-Simon Laplace. Encyclopaedia Britannica 15th ed.
Portrait: French postage stamp; public domain