Joseph-Louis Lagrange (1736 - 1813) was an Italian-born mathematician and astronomer who became one of the leading figures of eighteenth-century science. Working across Turin, Berlin, and Paris, he made lasting contributions to the calculus of variations, number theory, celestial mechanics, and the algebraic reformulation of classical mechanics.[1]
Early life
Lagrange was born in Turin, then the capital of the Kingdom of Sardinia, on 25 January 1736. He studied at the University of Turin, where an early interest in classical geometry gave way to the new analysis of Euler and the Bernoullis. Largely self-taught in advanced mathematics, he was appointed a teacher at the Royal Artillery School in Turin while still in his late teens.[2]
Career
In his early twenties Lagrange developed methods in the calculus of variations, correspondence on which drew the admiration of Leonhard Euler. He helped found the scientific society that became the Turin Academy of Sciences and published on a wide range of problems in mechanics and analysis. In 1766, on Euler's departure, he succeeded him as director of mathematics at the Prussian Academy of Sciences in Berlin, a post he held for two decades under Frederick the Great.[2]
In 1787 Lagrange moved to Paris, joining the Academy of Sciences. He remained in France through the Revolution and the Napoleonic era, serving on the commission that established the metric system and teaching at the newly created Ecole Polytechnique and Ecole Normale.[1]
Major work
Lagrange's most influential book, Mecanique analytique (1788), reformulated the whole of mechanics using algebra and analysis, deliberately avoiding geometric diagrams. He famously noted in its preface that the work contained no figures at all.[1]
His name endures across mathematics and physics in the Lagrangian formulation of mechanics, the Euler-Lagrange equations, Lagrange multipliers, Lagrange interpolation, and the Lagrange points of the three-body problem. He also proved important results in number theory, including the theorem that every natural number is the sum of four squares.[3]
Legacy
Lagrange was elected a Fellow of the Royal Society and was honoured in France as a Grand Officer of the Legion of Honour and a count of the Empire. He died in Paris on 10 April 1813 and was interred in the Pantheon. His surname is among the 72 names of scientists and engineers inscribed on the Eiffel Tower, and his analytical approach remains foundational to modern theoretical physics.[1]
