1 article for "Lagrange, Joseph"

**Lagrange, Joseph Louis Comte de**[Astro*Index]

(la-grahnzh')

(1736-1813) Italian-French astronomer and mathematician. Born at Turin, Piedmont; died at Paris, France.

He was born and raised in Italy, although of French ancestry. He taught geometry at the Royal Artillery School in Turin at age 18. He sent Euler a memorandum on the Calculus of Variations; Euler was greatly impressed and delayed publication of his own work in this area, in order to allow Lagrange to publish first. Lagrange and D'Alembert were appointed to the Berlin Academy, at the recommendation of Euler. With the aid of the Calculus of Variations, Lagrange formulated generalized equations from which all the problems in mechanics could be solved, summarizing his techniques in Analytical Mechanics, which was published in Paris in 1788. This work is unique, as it contained no geometric diagrams; it was completely algebraic (i.e., analytic). In astronomy, Lagrange studied the movement of bodies in systems containing more than two bodies (e.g., Earth-Moon-Sun or Jupiter with 4 moons). His investigation of 3-body systems showed that a stable condition exists at the two libration points which form equilateral triangles with the two most massive bodies; if a third body (of small mass) is located at either of these points, it will remain there. The Trojan System, which consists of the Sun, Jupiter, and certain asteroids is such a system. Astronomers have delighted in publishing papers on this subject, which is known as the Restricted Three-Body Problem. Lagrange's work on Perturbations did much to advance the field of Celestial Mechanics. His mathematical contributions were extensive, and include an important formula known as Lagrangian Interpolation. At the end of the French Revolution, he was appointed to head a commision to design a new system of weights and measures. With other members, which included Laplace and Lavoisier, they devised the Metric System, which is now used in virtually all countries. Although the United States has made some conversions to this system, it lags the remainder of the world in this area.

See also:

♦ Euler, Leonhard ♦ Laplace, Pierre Simon ♦ Libration ♦ Lagrangian Points

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