Historical Figures in Astronomy   by: Carmen Rush

Joseph Louis Lagrange

Although Lagrange is more famous for his contributions to mathematics, he also did work in astronomy. I’ll talk about this after giving you some information about his background.

Joseph-Louis Lagrange was born in Turin in 1736. His father was French and was Treasurer of the Office of Public Works and Fortifications in Turin. His mother was Italian and the only daughter of a medical doctor. Lagrange was the eldest of 11 children and was one of two to live to adulthood. Though officially Italian by birth, he always felt more French and would sign his name as Lagrange rather than Lagrangia as the family was known in Italy. Despite the fact that Lagrange’s father held a position of some importance in the service of the King of Sardinia, the family was not wealthy. His father had lost a large sum of money in unsuccessful financial speculations. The family planned a career in law for the boy and it seems that Lagrange accepted this at first. He studied at the College of Turin and his favorite subject was Latin. He showed no enthusiasm for math and found Greek geometry dull. But as luck would have it, he had an excellent physics teacher and was given a copy of Halley’s work on the use of algebra in optics. This branch of math completely won him over and he decided to devote himself to the subject.

Lagrange was largely self taught and did not have the benefit of studying with leading mathematicians. By 18 he published his first work on the binomial theorem and by 19 he made important discoveries in the calculus of variations. These results were sent to Euler, and so impressed was he by Lagrange’s work that he had him appointed as professor of mathematics at the Royal Artillery School in Turin. This was quite a feat for a young man of 19! A multi-talented mathematician and scientist, Lagrange continued with work on the calculus of probabilities, dynamics, kinetic energy, sound, vibrating strings, fluid mechanics and linear differential equations. Then came astronomy!

By this time Lagrange turned his study to the orbits of Jupiter and Saturn. Then in 1762 the Academie des Sciences in Paris announced its prize competition for 1764. The topic was on the libration of the Moon, that is the motion of the Moon which causes the face that it presents to the Earth to oscillate, causing small changes in the position of the lunar features. Lagrange entered the competition and sent his entry to Paris in 1763. He decided to go there himself, accompanying the Mauquis Caraccioli, an ambassador from Naples who was moving from a post in Turin to London. No sooner had he arrived in Paris, he took ill and was bedridden for 6 weeks. Interestingly enough, it was his illness that attracted as much attention as his entry in the competition. His work did not win him a prize but it, and the fact that he was very ill, attracted the attention and sympathy of D’Alembert who remarked that such a talented man was not appreciated by his native Turin and deserved a higher position in the scientific community. D’Alembert had very powerful connections with the Berlin Academy and was friendly with Frederick II of Prussia and arranged for Lagrange to be offered a post there. Lagrange was too modest to accept, remarking that he could not possibly accept with such great names as Euler being present.

By 1766 Lagrange was busy with astronomy again. He wrote a paper on the moons of Jupiter and entered it in a competition for the Academie des Sciences prize of 1766. This prompted D’Alembert to again press him to accept the position at the Berlin Academy. Lagrange finally accepted, noting that it was now more appropriate since Euler had left for St. Petersburg. Lagrange was too modest, since as soon as he arrived he was appointed Director of Mathematics at the Berlin Academy of Science. Not everyone was pleased to see him. Many of the older scientists felt threatened by this young upstart and did not make him feel welcome. Turin had lost a great scientist. Lagrange was very active in astronomy, studying the stability of the solar system, in mathematics, notably calculus and probability, and in mechanics and fluid mechanics.

A year later Lagrange married his cousin Vittoria Conti. Unfortunately she suffered years of ill health and the couple had no children. Her death in 1783 affected him deeply and he suffered from bouts of depression and overwork. His health remained poor. Perhaps as a result, he decided to leave Berlin and accept a post at the Academie of Sciences in Paris in 1787. He was lucky to survive the French Revolution when many others did not. This was probably due to his attitude that: “one of the first principles of every wise man is to conform strictly to the laws of the country in which he is living, even when they are unreasonable.”

It was at this time, in 1788, that Lagrange published his most famous work, the Mecanique Analytique. It summarized all the work done in mechanics since the time of Newton and transformed the subject into a branch of mathematical analysis. It was unique for its time in that it had no diagrams!

Lagrange was appointed to a committee in 1790 to standardize weights and measures. The metric system was born. It was at this time that he married for the second time, his teenage wife being Renee-Francoise Le Monnier, the daughter of one of his astronomer colleagues at the Academie. In 1793 the Academie fell victim to the Reign of Terror. Fortunately only the weight and measures committee he chaired survived. Fortunately again, Lavoisier successfully intervened on his behalf when a new law was passed in 1793 ordering the confiscation of all property owned by foreigners born in enemy countries and their arrest . Lagrange survived but Lavoisier did not. He along with 27 other scientists was guillotined in 1794 after a trial that lasted less than a day.

Lagrange was again fortunate. He was appointed as the first professor of analysis at the newly formed Ecole Polytechnique. Then in 1795 The Ecole Normale was founded for training teachers, and Lagrange taught elementary mathematics there. Fourier was one of his students. Lagrange was not a good teacher, as he remarked: “His voice is very feeble, at least in that he does not become heated; he has a very pronounced Italian accent and pronounces the s like a z. The students, of whom the majority are incapable of appreciating him, give him little welcome, but the professors make amends for it.”

Unpopular as he was as a teacher, Lagrange remained a well respected and a well published scientist. So impressed was Napoleon with him that he named Lagrange to the Legion of Honor and Count of the Empire in 1808. On April 3, 1813, he was named Grand Croix of the Imperial Order. He died a week later, at the ripe old age of 77.

This page last modified: January 8, 2003