Pierre-Simon Laplace

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Lore & Background

Laplace was born in Beaumont-en-Auge, Normandy on 23 March 1749, to Pierre Laplace and Marie-Anne Sochon, from comfortable families. His father was a cider merchant and syndic of the town. Laplace attended a Benedictine priory school, his father intending that he be ordained in the Roman Catholic Church. At sixteen, he was sent to the University of Caen to read theology. There, teachers Christophe Gadbled and Pierre Le Canu awakened his zeal for mathematics, and he wrote a memoir, Sur le Calcul integral aux differences infiniment petites et aux differences finies, which led to correspondence with Lagrange. Recognizing no vocation for the priesthood, he left for Paris with a letter of introduction to d'Alembert. According to his great-great-grandson, d'Alembert initially received him poorly, giving him a thick mathematics book, saying to come back when he had read it; when Laplace returned a few days later having read it, d'Alembert took him under his care. Another account says Laplace solved overnight a problem that d'Alembert set him for submission the following week, then solved a harder problem the following night, impressing d'Alembert, who recommended him for a teaching place in the École Militaire. From 1771 to 1787, Laplace produced much of his original work in astronomy. From 1780 to 1784, he collaborated with French chemist Antoine Lavoisier on several experimental investigations, designing their own equipment. In 1783 they published their joint paper, Memoir on Heat, discussing the kinetic theory of molecular motion, and measured the specific heat of various bodies, the expansion of metals with increasing temperature, and the boiling points of ethanol and ether under pressure. Laplace was elected associate member of the French Academy of Sciences on 31 March 1773 at age 24, after earlier rejections. On 15 March 1788, at age thirty-nine, he married Marie-Charlotte de Courty de Romanges, an eighteen-year-old girl from a 'good' family in Besançon; they had a son, Charles-Émile (1789–1874), and a daughter, Sophie-Suzanne (1792–1813). Laplace became a Count of the Empire in 1806 and was named a marquis in 1817, after the Bourbon Restoration.

Reader's Guide

Laplace's significance lies in his synthesis and extension of prior work into a coherent mathematical framework. His five-volume Mécanique céleste (1799–1825) transformed celestial mechanics by replacing geometric methods with calculus, enabling the solution of broader problems. He formulated Laplace's equation and pioneered the Laplace transform, which appears in many branches of mathematical physics, a field he took a leading role in forming. The Laplacian differential operator, widely used in mathematics, is also named after him. He restated and developed the nebular hypothesis of the origin of the Solar System and was one of the first scientists to suggest an idea similar to that of a black hole, with Stephen Hawking stating that 'Laplace essentially predicted the existence of black holes.' He originated Laplace's demon, a hypothetical all-predicting intellect. He also refined Newton's calculation of the speed of sound to derive a more accurate measurement. In statistics, the Bayesian interpretation of probability was developed mainly by Laplace. His work on probability and statistics was interlinked with his celestial mechanics; he took probability as an instrument for repairing defects in knowledge. Laplace is regarded as one of the greatest scientists of all time, sometimes referred to as the French Newton or Newton of France, possessing a phenomenal natural mathematical faculty superior to that of almost all of his contemporaries. He was Napoleon's examiner when Napoleon graduated from the École Militaire in Paris in 1785.

Did You Know?

• Laplace was Napoleon's examiner when Napoleon graduated from the École Militaire in Paris in 1785.
• He collaborated with chemist Antoine Lavoisier from 1780 to 1784, designing their own equipment for experiments on heat.
• Laplace's great-great-grandson reported that d'Alembert initially gave Laplace a thick mathematics book to read; Laplace returned a few days later having read it.
• He became a Count of the Empire in 1806 and was named a marquis in 1817 after the Bourbon Restoration.
• Stephen Hawking stated that 'Laplace essentially predicted the existence of black holes.'