Jean le Rond d’Alembert

Jean le Rond d’Alembert (1717–1783) was a French mathematician, physicist, and Enlightenment philosopher who co-edited the Encyclopédie and developed influential work on mechanics, waves, and mathematics.

D’Alembert’s principle: A mechanics principle that treats ideal constraints through virtual displacements and transforms dynamics into equilibrium-like equations. This principle is his signature contribution to analytical mechanics.
Vibrating string: A stretched string whose transverse motion produces waves and musical tones. Its motion prompted his influential derivation of the wave equation.
Paris Academy of Sciences: A French scientific institution founded in 1666 to advance and assess research. D’Alembert became a leading member and contributed to its mathematical culture.
Denis Diderot: A French philosopher, writer, and art critic who co-edited the Encyclopédie. Diderot and d’Alembert jointly led the Encyclopédie’s early editorial project.
Encyclopédie: An expansive French reference work edited by Denis Diderot and Jean le Rond d’Alembert from 1751 to 1772. D’Alembert co-edited its early volumes and wrote its influential preliminary discourse.
Wave equation: A partial differential equation describing how waves propagate through space and time. D’Alembert derived the one-dimensional wave equation while studying vibrating strings.
Three-body problem: The problem of predicting the motion of three mutually gravitating bodies. D’Alembert studied celestial mechanics and sought mathematical solutions to gravitational problems.
Collège des Quatre-Nations: A Paris college founded by Cardinal Mazarin and opened in 1688. He studied there before turning to mathematics and natural philosophy.
Voltaire: A French Enlightenment writer known for satire, plays, histories, and advocacy of civil liberties. D’Alembert corresponded with Voltaire and shared his challenges to religious authority.
Discours préliminaire de l’Encyclopédie: D’Alembert’s 1751 introduction to the Encyclopédie, presenting an account of knowledge and its history. It set out the intellectual program for the encyclopedia he co-edited.

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