Mathematician, b. 25 1anuary 1736 (Turin, Sardinia-Piedmont, Italy), d. 10 April 1813 (Paris, France).
Lagrange came from a wealthy French family that lost its fortune through speculation. His father had been treasurer to the king of Sardinia (Italy). The young Guiseppe Luigi had to find employment and taught mathematics at the artillery school of Turin before he turned 20.
Lagrange's interest in mathematics began with the reading of a work by the English astronomer Edmond Halley. He soon showed an extraordinary gift, was praised by Euler and at the age of 25 already recognized as one of the greatest mathematicians of his time. He was instrumental in setting up the Academy of Science of Turin.
The Paris Academy of Sciences regularly offered prizes for essays on selected difficult problems. Lagrange was awarded the prize in 1764, 1766, 1772, 1774 and 1778. Euler recommended Lagrange as his successor when he left Berlin in 1766. The Prussian king Frederick promptly invited Lagrange to his capital so that "the greatest king in Europe" could have "the greatest mathematician in Europe" at his court.
Lagrange worked in Berlin until the death of Frederick the Great in 1787. He then moved to Paris, following an invitation of Louis XVI, and lived in an apartment in the Louvre. During the French Revolution he served on the committee for a metric system of units and joined the mathematician Gaspar Monge one of the first professors of mathematics at the École Polytechnique shortly after it opened in 1794. Napoleon honoured Lagrange by making him a senator and a count of the empire. Lagrange died in Paris on 10 April, 1813.
Lagrange left a wealth of articles and books, most of them in French, on subjects as various as the principles of mechanics, the theory of analytic functions, prime-number theory and generalized coordinates. The equations which form the basis for classical mechanics now bear his name. Among his most important works are
The last two works were the result of Lagrange's lecturing activity at the École Polytechnique, still one of the most prestigious teaching institutions of France.
His Méchanique Analytique became the standard textbook for the field. In it he developed a method for the description of flow in fluids and gases based on the technique of following particles. The method is complementary to the method developed by Euler and widely used in fluid dynamics today.
Although continuously honoured throughout his life, Lagrange remained the quiet, unobtrusive and kind man he was when he began his lecturing career at the artillery school. When Lavoisier was sent to the guillotine, Lagrange remarked: "It required only a moment to sever his head, and perhaps a century will not be sufficient to produce another like it."
Lagrange's outstanding achievements are more the result of an extraordinary gift for mathematics then strong motivation. Looking back on his life, he said: "If I had been rich, I probably would not have devoted myself to mathematics."
Struik, D. J. (1995) Joseph-Louis Lagrange. Encyclopaedia Britannica 15th ed.
Portrait: engravong by Robert Hart, British Museum; public domain (Wikipedia)