A kilometer is about .621 miles. The U.S. uses the imperial system, but it is widely accepted around the world that the metric system is much simpler in terms of conversion: one kilometer is 1,000 meters, one kilogram is 1,000 grams, etc. Many countries didn’t always have the imperial system, like Britain. However, strong advocacy led to their eventual switch to the metric system, and Joseph-Louis Lagrange was a strong advocate for that change.

A French but self-considered Piedmontese scientist, Lagrange has made significant contributions to the field of mathematics. Born into an aristocratic family in Turin, Piedmont, on January 25, 1736, Lagrange had never found interest in mathematics as a child; it bored him. He planned to be like his father and study law. However, once he read a paper regarding lenses and algebra, he began to research and, at only 14 years old, became a student at the University of Turin. He quickly developed a habit of staying up for long hours of work through the aid of coffee and tea. At age 18, Lagrange published his first mathematical work, called Letter to Giulio Carlo de Fagnano. In this work, he described his discovery that the binomial expansion and the formula for the differential of a product have identical coefficients. Only a year later, he sent a paper to Leonhard Euler (at the time, the world’s greatest mathematician). He described his new method for finding maxima and minima of functions, a development that was crucial to calculus. A month later, in September of 1755, Euler wrote back and expressed his great admiration for Langrage’s work. 

A few days later, Lagrange accepted an offer from the Royal Military Academy to be an assistant professor of mathematics, leaving the University of Turin without a degree. His students were all older than him, and he had a rough start teaching. He was timid and held lectures too advanced for his students. Despite this work, he continued his advancements and developed his theory of sound and solved various dynamic problems, and in 1764, he won the French Academy of Sciences’ Prize for his study on why only one face of the moon is seen. Two years later, he won the same award again, but this time for explaining the orbit of Jupiter’s moons.

At the age of 30, Lagrange moved to Berlin and replaced Euler as the Director of Mathematics at the Prussian Academy of Sciences. The Academy had been trying to attract him since he was 19, but he continually refused because he felt like he would be in Euler’s shadow. Later, in the early 1780s, he completed his masterpiece, Analytical Mechanics, producing his Lagrangian function, but was unable to find a publisher for several years. Lagrange also created the notation f’(x) for the derivative of a function and the word derivative itself, also introducing the concept of a generalized coordinate system and potential fields like gravity fields. 

Sophie Germain, excluded from the Polytechnique because she was a woman, obtained his Analysis lecture notes and was astonished. Writing letters to him, he responded and spread the word about her brilliance.

Lagrange died at the age of 77 on April 10, 1813. He had a wife of 45 years named Renée-Françoise-Adélaide Le Monnier. Lagrange’s contributions to the field of mathematics were so influential that when the Eiffel Tower opened in 1889, Lagrange was one of the 72 French scientists, engineers, and mathematicians whose names were engraved on plaques on the tower. If you ever travel to Britain, remember that Lagrange is a large reason for their adoption of the metric system…and that a kilometer is shorter than a mile.