Louis Marcel Brillouin (French: [b?ilw?~]; 19 December 1854 – 16 June 1948) was a French physicist and mathematician.
Born in Saint-Martin-lès-Melle, Deux-Sèvres, France, his father was a painter who moved to Paris when Marcel was a boy.
He became a physics assistant to Eleuthere Mascart (his future father-in-law) at the Collège de France, while at the same time working for his doctorates in mathematics and physics, which he gained in 1880 and 1882, respectively.
Later, he was Professor of Mathematical Physics at the Collège de France from 1900 to retirement in 1931.
In 1911 he was one of only six French physicists invited to the first Solvay Conference.
He was an officer of the Legion of Honour.During his career he was the author of over 200 experimental and theoretic papers on a wide range of topics which include the kinetic theory of gases, viscosity, thermodynamics, electricity, and the physics of melting conditions.
Most notably he:
built a new model of the Eötvös balance,
wrote on Helmholtz flow and the stability of aircraft,
worked on a theory of the tides.Brillouin died in Paris (16 June 1948).