Jean le Rond d'Alembert
"d'Alembert" redirects here. For other uses, see d'Alembert (disambiguation).
Jean-Baptiste le Rond d'Alembert (/ثŒdأ¦lة™mثˆbة›ة™r/;[1] French:*[ت’ة‘جƒ batist lة™ تپة”جƒ dalة‘جƒbة›ثگتپ]; 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.[2][3][4] The wave equation is sometimes referred to as d'Alembert's equation.

Jean le Rond d'Alembert

Jean-Baptiste le Rond d'Alembert, pastel by Maurice Quentin de La Tour
Born Jean-Baptiste le Rond d'Alembert
16 November 1717
Paris, France
Died 29 October 1783 (aged*65)
Paris, France
Nationality French
Alma*mater University of Paris
Known*for D'Alembert criterion
D'Alembert force
D'Alembert's form of the principle of virtual work
D'Alembert's formula
D'Alembert equation
D'Alembert's equation
D'Alembert operator
D'Alembert's paradox
D'Alembert's principle
D'Alembert system
D'Alembert–Euler condition
Tree of Diderot and d'Alembert
Cauchy–Riemann equations
Fluid mechanics
Encyclopédie
Three-body problem
Awards Fellow of the Royal Society
Follow of the Institut de France
Scientific career
Fields Mathematics
Mechanics
Physics
Philosophy
Notable students Pierre-Simon Laplace
Early years Edit

Born in Paris, d'Alembert was the natural son 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. Days after birth his mother left him on the steps of the Saint-Jean-le-Rond de Paris*(fr) church. According to custom, he was named after the patron saint of the church. D'Alembert was placed in an orphanage for foundling children, but his father found him and placed him with the wife of a glazier, Madame Rousseau, with whom he lived for nearly 50 years.[5] Destouches secretly paid for the education of Jean le Rond, but did not want his paternity officially recognised.

Studies and adult life Edit

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 Frederick the Great of Prussia for a suspected (but non-existent) moon of Venus.[6]

Career Edit

In July 1739 he made his first contribution to the field of mathematics, pointing out the errors he had detected in Analyse démontrée (published 1708 by Charles-René Reynaud) in a communication addressed to the Académie des Sciences. At the time L'analyse démontrée was a standard work, which d'Alembert himself had used to study the foundations of mathematics. D'Alembert was also a Latin scholar of some note and worked in the latter part of his life on a superb translation of Tacitus, for which he received wide praise including that of Denis Diderot.

In 1740, he submitted his second scientific work from the field of fluid mechanics Mémoire sur la réfraction des corps solides, which was recognised by Clairaut. In this work d'Alembert theoretically explained refraction.

In 1741, after several failed attempts, d'Alembert was elected into the Académie des Sciences. He was later elected to the Berlin Academy in 1746[7] and a Fellow of the Royal Society in 1748.[8]

In 1743, he published his most famous work, Traité de dynamique, in which he developed his own laws of motion.[9]

When the Encyclopédie was organised in the late 1740s, d'Alembert was engaged as co-editor (for mathematics and science) with Diderot, and served until a series of crises temporarily interrupted the publication in 1757. He authored over a thousand articles for it, including the famous Preliminary Discourse. D'Alembert "abandoned the foundation of Materialism"[10] when he "doubted whether there exists outside us anything corresponding to what we suppose we see."[10] In this way, D'Alembert agreed with the Idealist Berkeley and anticipated the Transcendental idealism of Kant.

In 1752, he wrote about what is now called D'Alembert's paradox: that the drag on a body immersed in an inviscid, incompressible fluid is zero.

In 1754, d'Alembert was elected a member of the Académie des sciences, of which he became Permanent Secretary on 9 April 1772.[11]

In 1757, an article by d'Alembert in the seventh volume of the Encyclopedia suggested that the Geneva clergymen had moved from Calvinism to pure Socinianism, basing this on information provided by Voltaire. The Pastors of Geneva were indignant, and appointed a committee to answer these charges. Under pressure from Jacob Vernes, Jean-Jacques Rousseau and others, d'Alembert eventually made the excuse that he considered anyone who did not accept the Church of Rome to be a Socinianist, and that was all he meant, and he abstained from further work on the encyclopaedia following his response to the critique.[12]