Joseph Louis Lagrange

Joseph Louis Lagrange (1736-1813), French mathematician and astronomer, born in Turin, Italy, and educated at the University of Turin. He was appointed professor of geometry at the Turin military academy at the age of 19, and in 1758 he founded a society that later developed into the Turin Academy of Sciences. In 1766 he was appointed director of the Berlin Academy of Sciences and 20 years later, at the invitation of King Louis XVI of France, went to Paris. During the period of the French Revolution he was in charge of the commission for establishing a new system of weights and measures (see Metric System). He was made professor in the newly established École Normale after the French Revolution, and under Napoleon he was made a member of the Senate and given the rank of count. One of the greatest mathematicians of the 18th century, he created the calculus of variations, systematized the field of differential equations, and worked on the theory of numbers. Among his investigations in astronomy were calculations of the libration of the moon and motions of the planets. His greatest work is Mécanique analytique (1788).