Joseph Lagrange Biography

      Joseph Louis Lagrange, an Italian-born French mathematician, was born on January 25, 1736 and lived until April 10, 1813. Lagrange made a number of significant contributions to the fields of mathematics and astronomy. He had a propensity for math as a child and was a mostly self-taught mathematician. He also developed his own methods, which he called 'Calculus of variation'. By age 25 he was recognized as one of the greatest living mathematicians because of his papers on wave propagation and maxima and minima of curves. He became renowned for his textbook Mécanique analytique (1788), which is used today as a base for modern mathematicians. 

Diagram of Lagrangian points. L2 is the smaller satellite that
would be, in theory, stationary under the influence of the
 gravitational forces of the Earth and Moon.

      

     Joseph Lagrange largely contributed to celestial mathematics. In 1772, he created what is known as Lagrangian points (or libration points), which served as a solution to the three-body problem. Lagrangian points are the five different positions within an orbital, where a smaller celestial astronomical object could be relatively stationary to two other larger objects, for instance, a satellite relative to the Earth and Moon. The Lagrange are where the combined gravity of the two larger objects would cancel the centripetal force (the force that causes objects to follow a curved path) required to for the smaller object rotate with them. At Lagrange's time, this was merely a theory, however in 1906 Trojan Asteroids moving in Jupiter's orbit became the first examples, as the Trojans were relatively stable under the gravitational pulls of Jupiter and the Sun. Lagrangian mechanics (re-formulations of the laws of conservation of momentum and energy) were a large accomplishment as well as they simplified some earlier difficulties in mathematical equations. 

          Many other discoveries and papers are credited to Lagrange about subjects, some of which including: motion of planetary nodes, the secular equation of the Moon, stability of planetary orbits, interpolation and the attraction of ellipsoids.