Sergei Alexander Korff was born in Helsingfors, Finland, in 1906. Immigrating to the United States with his family in 1917, he became a citizen in 1927. Korff attended Princeton receiving his A.B. in 1928, M.A. in 1929 and Ph.D. in 1931. Between 1932 and 1940, he completed research fellowships at the Mt. Wilson Observatory, the California Institute of Technology, the Carnegie Institute of Washington, and the Bartol Research Foundation. Collaborating with eminent physicists in his early work, Korff investigated topics such as optical dispersion, proportional counters and neutron measurements in cosmic radiation. Korff began his tenure at New York University in 1941, and continued there until his death in 1989. He helped train at least three generations of students, taking many on research expeditions as far away as the North Pole and the South Seas.

In addition to his teaching and research, Korff lent his efforts to the international scientific community. He compiled the report of the Joint Commission on High Altitude Research for ICSU-UNESCO; served on the Cosmic Ray Technical Panel for the International Geophysical Year, 1957-58; organized the pole-to-pole Rockwell Scientific Round-the-World Flight in 1965; and encouraged and secured support for scientific work around the world, particularly in Central and South America. Notable among his numerous professional affiliations were his terms as president of the Explorer's Club (1955-1958); the American Geographical Society (1966-1971); and New York Academy of Science (1972). For his efforts to transfer surplus scientific equipment to the decimated laboratories of France after World War II, in 1952 Korff was decorated Chevalier of the Legion of Honor. For the contribution of his radiation detection devices to the study of cancer, he was awarded the Curie Medal of the International Union Against Cancer.

Korff's Counter Project and Cosmic Ray Project attracted numerous students to NYU; many later achieved prominence as physicists. The project also brought the university substantial funding from government agencies, such as the National Air and Space Agency and the National Science Foundation. Author of over 150 scientific papers and books, as well as a number of works on exploration, geology and stamps, Korff's contributions to science went beyond the study of cosmic rays. His ability to render complex scientific issues exciting and clear to the general public in encyclopedia and newspaper articles, and to expose the subtleties of science to his students and peers, marked Korff as an outstanding figure in 20th century physics.