# Laplace, Pierre Simon, Marquis de

### mechanics celestial newton orbits

[lahplas] (1749–1827) French mathematician, astronomer and mathematical physicist: developed celestial mechanics; suggested hypothesis for origin of the solar system.

Although from a poor family, Laplace’s talent led him to become an assistant to in thermo-chemistry. Later he moved to astronomy, and became a minister and senator, skilfully contriving to hold a state office despite violent political changes. Laplace’s most important work was on celestial mechanics. In 1773 he showed that gravitational perturbations of one planet by another would not lead to instabilities in their orbits ( Had believed that such small irregularities would, without divine intervention, eventually lead to the end of the world). He later proved two theorems involving the mean distances and eccentricities of the planetary orbits and showed that the solar system has long-term stability. In 1796 Laplace proposed in a note that the Sun and planets were formed from a rotating disc of gas; he did not know that had made a similar suggestion; modified forms of this nebular hypothesis are still accepted. Between 1799 and 1825 he published his five-volume opus *Mécanique céleste* (Celestial Mechanics), which incorporated developments in celestial mechanics since Newton as well as his own important contributions. (The book has its oddity: frequently the phrase ‘it is obvious that’ occurs, in mathematical equations, when it is far from obvious. And Napoleon is said to have remarked, critically, that it made no mention of God.) Laplace is also remembered for putting probability theory on a firm foundation, and for developing the concept of a ‘potential’ and its description by the Laplace equation. In the fields in which Laplace worked and where Newton had worked previously, he is seen as second only to Newton in his talent.

## User Comments

almost 6 years ago

This entry requires copy editing; some words or names have dropped out of some of the opening sentences. For knowledgeable readers they are not hard to surmise, but they shall hinder others. Just thought I'd mention. It's *great* to have this edition on-line!! -- KRW