Jean-Baptiste le Rond d’Alembert was a French mathematician, mechanician, physicist, philosopher, and music theorist. Until 1759 he was, together with Denis Diderot, a co-editor of the Encyclopédie. D’Alembert’s formula for obtaining solutions to the wave equation is named after him.
Jean-Baptiste le Rond d’Alemberts formula for obtaining solutions to the wave equation is named after him. The wave equation is sometimes referred to as d’Alembert’s equation, and the fundamental theorem of algebra is named after d’Alembert in French.
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. D’Alembert first attended a private school. At the age of 12 d’Alembert entered the Jansenist Collège des Quatre-Nations. Here he studied philosophy, law, and the arts, graduating as baccalauréat en arts in 1735. He entered law school for two years, and was nominated avocat in 1738. He was also interested in medicine and mathematics.
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. He was later elected to the Berlin Academy in 1746and a Fellow of the Royal Society in 1748. In 1743, he published his most famous work, Traité de dynamique, in which he developed his own laws of motion.
When the Encyclopédie was organised in the late 1740s, d’Alembert was engaged as co-editor (for mathematics and science) with Diderot. He authored over a thousand articles for it, including the famous Preliminary Discourse. D’Alembert “abandoned the foundation of Materialism”when he “doubted whether there exists outside us anything corresponding to what we suppose we see.” 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.
He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1781.D’Alembert also discussed various aspects of the state of music in his celebrated Discours préliminaire of Diderot’s Encyclopédie