Laplace set out to show the Solar System needed no divine repairs
Isaac Newton suspected the planets' tugs on one another would slowly wreck the Solar System unless God stepped in now and then. Pierre-Simon Laplace spent much of his life trying to prove otherwise, carrying the mathematics further than Euler or Lagrange had and explaining why Jupiter and Saturn seemed to drift.
Laplace was born on 23 March 1749 in Beaumont-en-Auge, Normandy. An old story made him a poor farm boy, but his father owned a small estate and also sold cider. Sent at sixteen to the University of Caen to train for the priesthood, he was won over to mathematics by two teachers there, and before turning twenty he was writing to Lagrange in Turin, whose journal printed his first paper.
He arrived in Paris in 1771 with an introduction to Jean d'Alembert, the leading scientist of the day. By one family account, d'Alembert handed him a fat mathematics book to be rid of him, doubted he could have mastered it days later, then questioned him and took him on. A teaching job at the École Militaire followed, where in 1785 he examined a graduating cadet named Napoleon. The Academy of Sciences passed him over twice before electing him in 1773, at 24.
Planetary orbits had puzzled Euler and Lagrange, who dropped small terms from their equations. Laplace saw that tiny effects can accumulate over long spans, and by keeping terms up to the cubic he concluded that each pair of planets and the Sun stay in balance. In 1775 he produced a dynamic theory of tides that allowed for friction and the resonances of ocean basins. From 1780 he and Antoine Lavoisier built their own apparatus to measure specific heats and how metals expand when warmed.
His five-volume Celestial Mechanics recast Newtonian physics in the language of calculus. He shaped the Bayesian view of probability, proposed an early form of the black hole idea, imagined an all-knowing intellect later called Laplace's demon, and left his name on an equation, a transform and an operator. Napoleon made him a count in 1806, the restored Bourbons a marquis in 1817. Many of his papers burned with a family château in 1925. He died in 1827.
Source: Pierre-Simon Laplace
