Joseph Louis Lagrange

In 1767, Lagrange married his cousin Vittoria Conti. They did not have any children. From his letters to d'Alembert, some scholars have deduced that he did not wish to have any.

In 1783, Vittoria died after years of illness, leaving Lagrange very depressed.

In 1792, he married 24 year old Renee-Francoise-Adelaide Le Monnier, the daughter of his colleague, Pierre Charles Le Monnier. It is said that she insisted that he marry her and was very devoted until his death on 10 April, 1813 in Paris.

Joseph Louis Lagrange was born Giuseppe Lodovico Lagrangia on 25 January, 1736 in Turin, Italy. His father, Giuseppe Francesco Lodovico Lagrangia, worked as a Treasurer in the Office of Public Works and Fortifications in Turin. His mother, Teresa Grosso, was the daughter of a doctor from nearby town of Cambiano.

Lagrange was the eldest of his parent’s two surviving children. As a young man, he often used the French form of his family name, calling himself Lodovico LaGrange.

He enrolled at the University of Turin to study law.

Initially he did not show much interest in mathematics. In fact, he found Greek geometry rather dull and was more interested in Classic Latin. At the age of seventeen, he accidentally came across a paper on the use of algebra in optics by Edmond Halley. It opened a new world for him.

Alone and unaided, he began to study mathematics and within a year, became a skilled mathematician. On 23 July 1754, he published his first mathematical work in the form of a letter written to Italian mathematician Giulio Fagnano. In this work, he drew an analogy between the binomial theorem and the successive derivatives of the product of functions. Unfortunately, a month after the paper was published, he realized that the work had already appeared in correspondence between Johann Bernoulli and Leibniz.

On 28 September 1755, Lagrange was appointed as the ‘Sostituto del Maestro di Matematica’ (assistant professor in mathematics) at the Royal Military Academy of the Theory and Practice of Artillery by Charles Emmanuel III, the Duke of Savoy and the King of Sardinia. Thus he began his career at the age of 19.

At the Academy, he taught calculus and mechanics. Although he became well-known for the originality of his thoughts and depth of knowledge, his teaching style was not very popular. His abstract reasoning as well as his impatience with engineering applications also created problems.

In 1756, Lagrange applied calculus of variation to mechanism and sent the result to Leonhard Euler. Impressed, Euler showed the work to French mathematician, Pierre-Louis Moreau de Maupertuis, who at that time was the President of Berlin Academy.

Maupertuis was so impressed by Lagrange that he invited him to come to Prussia, offering better position than he had at Turin. However, he politely refused it, preferring to stay at Turin for the time being. Despite the refusal, Lagrange was elected to the Berlin Academy on 2nd September 1756.

In 1757, Lagrange formed a scientific society in Turin, which later came to known as Royal Academy of Sciences of Turin. It published a scientific journal called ‘Mélanges de Turin’, in which Lagrange sent regular contributions.

Lagrange is best known for his contribution to the development of the metric system. As President of la Commission des Poidset Mesures, he played a decisive role in taking up the unit system of meter and kilogram as well as their decimal subdivisions.

He is also considered as one of the founders of the calculus of variations. While working on the problem of tautochrone, he discovered a method of maximizing and minimizing functional, which led to development of calculus of variation.

‘Mécaniqueanalytique’, published in 1788, is another of his important work. He worked on this book for half a century and summarized all the work done in the field of mechanics since the time of Newton.