Pierre-Simon Laplace

• 1. A Boy From Normandy

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  Pierre-Simon Laplace was born on the 23rd of March 1749 in Beaumont-en-Auge, a small village four miles west of Pont l'Évêque. His father Pierre de Laplace owned and farmed the small estates of Maarquis while also serving as a cider merchant and syndic of the town. The family belonged to comfortable circles within the region, yet their son would leave behind the fields for Paris. At sixteen years old, he attended a school run at a Benedictine priory where his father intended him to be ordained into the Roman Catholic Church. Two enthusiastic teachers named Christophe Gadbled and Pierre Le Canu awakened his true zeal for mathematics instead of theology. He wrote a memoir titled Sur le Calcul integral aux differences infiniment petites et aux differences finies while still studying at Caen. This early work provided the first correspondence between Laplace and Joseph Louis Lagrange who was thirteen years older. Lagrange had recently founded a journal named Miscellanea Taurinensia in Turin where many of Laplace's early works appeared. Recognizing that he possessed no vocation for the priesthood, the young scholar resolved to become a professional mathematician.

• 2. The Five Volumes Of Mechanics

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  Laplace set himself the task to write a work which should offer a complete solution of the great mechanical problem presented by the Solar System. The result is embodied in the five-volume Mécanique céleste published between 1799 and 1825. The first two volumes appeared in 1799 containing methods for calculating planetary motions and resolving tidal problems. The third and fourth volumes followed in 1802 and 1805 with applications of these methods and several astronomical tables. The fifth volume arrived much later in 1825 as mainly historical material but included appendices of his latest researches. Jean-Baptiste Biot assisted Laplace in revising it for the press yet often found him unable to recover details in the chain of reasoning. If satisfied that conclusions were correct, Laplace would insert the phrase Il est aisé à voir que meaning It is easy to see that. This treatise translated Newton's Principia Mathematica into the language of differential calculus. It completed parts of which Newton had been unable to fill in the details regarding orbital stability without divine intervention. Historians describe the volume's conclusions as the organized result of a century of work by other writers alongside Laplace.

• 3. The Rule Of Succession

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  In 1812 Laplace issued his Théorie analytique des probabilités laying down many fundamental results in statistics. The first half concerned probability methods while the second half dealt with statistical methods and applications. One well-known formula arising from his system was the rule of succession given as principle seven. He calculated that the probability that the sun will rise tomorrow given that it has never failed to do so in the past was extremely high. Yet he immediately wrote that this number is far greater for him who realizes nothing at the present moment can arrest its course. His proofs are not always rigorous according to later standards and his perspective slides back and forth between Bayesian and non-Bayesian views. In two important papers published in 1810 and 1811 he developed the characteristic function as a tool for large-sample theory. He proved the first general central limit theorem showing how errors distribute when combining observations. This work remained the most influential book of mathematical probability theory until the end of the 19th century.

• 4. Transforms And Spherical Harmonics

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  Laplace formulated Laplace's equation which appears ubiquitously in mathematical physics across fluid dynamics and electromagnetism. He pioneered the Laplace transform though modern development dates from the work of Gustav Doetsch in the 1920s. In 1783 he introduced spherical harmonics or Laplace coefficients into analysis extending results previously found by Adrien-Marie Legendre. The sequence of functions P0k(cos φ) allows every function on points within a circle to be expanded as a series of them. These harmonics turn out critical to practical solutions of Laplace's equation in spherical coordinates used for mapping the sky. He completely determined the attraction of a spheroid on a particle outside it in a paper read in 1783. This work developed the use of what we would now call gravitational potential in celestial mechanics. The quantity nabla squared V has been termed the concentration of V indicating excess value over its mean neighborhood.

• 5. Six Weeks As Minister

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  In November 1799 Napoleon appointed Laplace to the post of Minister of the Interior immediately after seizing power in the coup of 18 Brumaire. The appointment lasted only six weeks before Lucien Bonaparte received the post instead. Evidently once Napoleon's grip on power was secure there was no need for a prestigious but inexperienced scientist in government. Napoleon later wrote of Laplace's dismissal claiming he knew nothing about administration yet historians describe these remarks as tendentious. From 1806 to 1814 Laplace served in various capacities including being raised to the senate. In 1814 it became evident that the empire was falling and Laplace hastened to tender his services to the Bourbons. During the Restoration in 1817 he was rewarded with the title of marquis. Roger Hahn disputes portrayals of him as an opportunist noting he followed the debacle of Napoleon's Russian campaign with serious misgivings. His daughter Sophie had died in childbirth in September 1813 leaving fear for their son Émile who was on the eastern front.

• 6. The Demon And Black Holes

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  In 1814 Laplace published what may have been the first scientific articulation of causal determinism through an intellect often referred to as Laplace's demon. This intelligence would know all positions and momenta making the future present to its eyes just like the past. He suggested gravity could influence light and massive stars might exist whose gravity is so great not even light could escape from their surface. Stephen Hawking stated that Laplace essentially predicted the existence of black holes though this insight played no role in history at the time. The concept remained far ahead of its era until modern astrophysics caught up. Laplace also refined Newton's calculation of the speed of sound to derive a more accurate measurement by pointing out dependence on heat capacity ratio. His work on tidal dynamics described ocean basins taking into account friction resonance and natural periods. These equations predicted large amphidromic systems explaining tides observed worldwide today.

• 7. A Name On The Tower

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  Laplace died in Paris on the 5th of March 1827 which was the same day Alessandro Volta died. His brain was removed by his physician François Magendie and kept for many years eventually displayed in a roving anatomical museum in Britain. It was reportedly smaller than the average brain. He was buried at Père Lachaise but in 1888 his remains were moved to Saint Julien de Mailloc reinterred on the family estate. A spur of the Montes Jura on the Moon bears his name as Promontorium Laplace. The asteroid 4628 Laplace carries his designation while his name appears among the 72 inscribed on the Eiffel Tower. A train station in Arcueil bears his name alongside streets named after him in Russia. The Institute of Electrical and Electronics Engineers Signal Processing Society honors him with an Early Career Technical Achievement Award. His Mécanique céleste remains a standard authority despite containing numerous results appropriated from other writers with little or no acknowledgement.