Louis Dunoyer


Louis Dunoyer
Versailles, France
Death date
Fields of study


Louis Dunoyer was a French physicist known for his contributions to the study of vacuums and meterology, and for inventing the first electromagnetic compass.

Dunoyer was born in Versailles in 1880. As a youth, he excelled in physics, winning admission to École Normale Supérieure. While at university, he worked with Paul Langevin as a research assistant. His first research focused on the problem of creating compasses for iron and iron-clad ships. This work led to his doctoral thesis and his development of the electromagnetic compass that Charles Lindbergh mounted in his plane, Spirit of St. Louis. In 1908, he won the Prix Extraordinare de la Marine for this research on magnetism.

In 1909, Dunoyer became a Carnegie scholar in Marie Curie’s laboratory. There, he conducted a critical experiment on molecular beams in 1912 that both verified the kinetic theory of gases and showed how thin films of alkali metals could be produced by thermal vaporization. This research earned Dunoyer awards and a professorship.

During World War I, he was wounded in his role as an aviation officer and inspector. He conducted wartime research into meteorology and aerial navigation and invented a bombsight. Dunoyer also won recognition, in 1918, for his work on radiant phenomena.

After the war, Dunoyer advanced through a series of physics professorships and researched new techniques in illuminating atomic beams, glassblowing, and measuring very low temperatures. He also pursued research on building photoelectric cells, which he applied to talking movies in 1925. His work on thermal vaporization in a vacuum allowed him to create the first aluminum mirrors in 1935. His contributions led one French scientific society to call him “Grandfather of the Vacuum.”