Jean le Rond d’Alembert

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Jean le Rond d'Alembert bigraphy, stories - French mathematician, physicist and philosopher

Jean le Rond d’Alembert : biography

16 November 1717 – 29 October 1783

Jean-Baptiste le Rond d’Alembert () (16 November 1717 – 29 October 1783) was a French mathematician, mechanician, physicist, philosopher, and music theorist. Until 1759 he was also co-editor with Denis Diderot of the Encyclopédie. D’Alembert’s formula for obtaining solutions to the wave equation is named after him.D’Alembert (1747) (Researches on the curve that a tense cord forms [when] set into vibration), Histoire de l’académie royale des sciences et belles lettres de Berlin, vol. 3, pages 214-219. See also: D’Alembert (1747) (Further researches on the curve that a tense cord forms [when] set into vibration), Histoire de l’académie royale des sciences et belles lettres de Berlin, vol. 3, pages 220-249. See also: D’Alembert (1750) Histoire de l’académie royale des sciences et belles lettres de Berlin, vol. 6, pages 355-360. The wave equation is sometimes referred to as D’Alembert’s equation.

Legacy

In France, the fundamental theorem of algebra is known as the d’Alembert/Gauss theorem (an error in d’Alembert’s proof was caught by Gauss).

He also created his ratio test, a test to see if a series converges.

The D’Alembert operator, which first arose in D’Alembert’s analysis of vibrating strings, plays an important role in modern theoretical physics.

While he made great strides in mathematics and physics, d’Alembert is also famously known for incorrectly arguing in Croix ou Pile that the probability of a coin landing heads increased for every time that it came up tails. In gambling, the strategy of decreasing one’s bet the more one wins and increasing one’s bet the more one loses is therefore called the D’Alembert system, a type of martingale.

Death

He suffered bad health for many years and his death was as the result of a urinary bladder illness. As a known unbeliever, D’Alembert was buried in a common unmarked grave.

Studies and adult life

D’Alembert first attended a private school. The chevalier Destouches left d’Alembert an annuity of 1200 livres on his death in 1726. Under the influence of the Destouches family, at the age of twelve d’Alembert entered the Jansenist Collège des Quatre-Nations (the institution was also known under the name "Collège Mazarin"). Here he studied philosophy, law, and the arts, graduating as baccalauréat en arts in 1735. In his later life, D’Alembert scorned the Cartesian principles he had been taught by the Jansenists: "physical promotion, innate ideas and the vortices".

The Jansenists steered D’Alembert toward an ecclesiastical career, attempting to deter him from pursuits such as poetry and mathematics. Theology was, however, "rather unsubstantial fodder" for d’Alembert. He entered law school for two years, and was nominated avocat in 1738.

He was also interested in medicine and mathematics. Jean was first registered under the name Daremberg, but later changed it to d’Alembert. The name "d’Alembert" was proposed by Johann Heinrich Lambert for a suspected (but non-existent) moon of Venus.

Early years

Born in Paris, d’Alembert was the illegitimate child of the writer Claudine Guérin de Tencin and the chevalier Louis-Camus Destouches, an artillery officer. Destouches was abroad at the time of d’Alembert’s birth, and a couple of days after birth his mother left him on the steps of the Saint-Jean-le-Rond de Paris church. According to custom, he was named after the patron saint of the church. D’Alembert was placed in an orphanage for found children, but was soon adopted by the wife of a glazier. Destouches secretly paid for the education of Jean le Rond, but did not want his paternity officially recognized.

Music theories

D’Alembert’s first exposure to music theory was in 1749 when he was called upon to review a Mémoire submitted to the Académie by Jean-Philippe Rameau. This article, written in conjunction with Diderot, would later form the basis of Rameau’s 1750 treatise Démonstration du principe de l’harmonie. D’Alembert wrote a glowing review praising the author’s deductive character as an ideal scientific model. He saw in Rameau’s music theories support for his own scientific ideas, a fully systematic method with a strongly deductive synthetic structure.