Harold Calvin Marston Morse (March 24, 1892 – June 22, 1977) was an American mathematician best known for his work on the calculus of variations in the large, a subject where he introduced the technique of differential topology now known as Morse theory. The Morse–Palais lemma, one of the key results in Morse theory, is named after him, as is the Thue–Morse sequence, an infinite binary sequence with many applications. In 1933 he was awarded the Bôcher Memorial Prize for his work in mathematical analysis. Biography He was born in Waterville, Maine to Ella Phoebe Marston and Howard Calvin Morse in 1892. He received his bachelor's degree from Colby College (also in Waterville) in 1914. At Harvard University, he received both his master's degree in 1915 and his PhD in 1917. He wrote his PhD thesis, Certain Types of Geodesic Motion of a Surface of Negative Curvature, under the direction of George David Birkhoff. Morse was a Benjamin Peirce Instructor at Harvard in 1919–1920, after which he served as an assistant professor at Cornell University from 1920 to 1925 and at Brown University in 1925–1926. He returned to Harvard in 1926, advancing to professor in 1929, and teaching there until 1935. That year, he accepted a position at the Institute for Advanced Study in Princeton, where he remained until his retirement in 1962. He spent most of his career on a single subject, now known as Morse theory, a branch of differential topology that enables one to analyze the topology of a smooth manifold by studying differentiable functions on that manifold. Morse originally applied his theory to geodesics (critical points of the energy functional on paths); these techniques were used in Raoul Bott's proof of his periodicity theorem. Morse theory is a very important subject in modern mathematical physics, such as string theory. He died on June 22, 1977, at his home in Princeton, New Jersey. Marston Morse should not be confused with either his 5th cousin twice removed Samuel Morse, famous for Morse code, nor Anthony Morse, famous for the Morse–Sard theorem. Selected publications Articles Books with Stewart Cairns: Film "Pits, Peaks, and Passes: A Lecture on Critical Point Theory", Mathematical Association of America Lecture Films, 1966 Notes Biographical references . References . (e-book: ). 1892 births 1977 deaths 20th-century American mathematicians Colby College alumni Cornell University faculty Differential geometers Harvard University alumni Harvard University faculty Institute for Advanced