Today is the birthday of mathematician and astronomer Joseph-Louis Lagrange, who was born in Turin, Italy, in 1736. By age 18, Lagrange had published his first mathematical paper; by age 19, he was professor of mathematics at the Royal Artillery School in Turin. Because of his significant contributions in such areas as the calculus of variations, celestial mechanics (including the three-body problem), and the propagation of sound, Lagrange soon established a reputation as one of the greatest mathematicians in Europe. In 1766 Lagrange succeeded his academic adviser, Leonhard Euler, as director of mathematics at the Berlin Academy, where he would stay for the next two decades. In 1787 Lagrange moved from Berlin to Paris, where he became a member the French Academy of Sciences. The next year, he published one of his most important texts, Mécanique analytique, a groundbreaking synthesis of the 100 years of research in mechanics since Newton. In 1808, Napoleon named Lagrange to the Legion of Honor and made him a count of the empire. Today physics students learning mechanics are taught the Lagrangian, which describes the state of a dynamic physical system. Some space probes, including the soon-to-be-launched James Webb Space Telescope, are parked at Lagrangian points, where three bodies can orbit each other yet stay in the same relative positions.
