KAPLAN, JOSEPH (1902–1991), geophysicist. Kaplan was born in Tapolcza, Austro-Hungary, and moved with his family to Baltimore at the age of eight. He received his B.Sc. in chemistry in 1924 and his Ph.D. in physics in 1927 at Johns Hopkins University, Baltimore, after which he was a research fellow at Princeton University before moving to the University of California at Los Angeles (ucla) in 1928. He remained at ucla for the rest of his life. At ucla he was a full professor from 1940, chairman of the Department of Physics (1939–44), and director of the Institute of Geophysics (1946–47). Kaplan's laboratory work simulated the atomic and molecular reactions which occur in the earth's upper atmosphere. His subsequent work characterized the physical nature of nitrogen in the upper atmosphere and the atmospheric bands of oxygen which contribute to the light of the night sky. With colleagues he founded the science of "aeronomy," which studies the physics of the planetary atmosphere. Kaplan was an enthusiastic undergraduate and graduate teacher. He also contributed to the World War ii program training U.S. Army Air Force weather officers. He was an outstanding contributor to international organizations concerned with geophysics, including the presidency of the International Union of Geodesy and Geophysics (1963). His many honors included membership in the U.S. National Academy of Sciences (elected 1957). He was an honorary member of the Board of Governors of the Hebrew University of Jerusalem and a member of the Board of Governors of the Weizmann Institute of Science.
[Michael Denman (2nd ed.)]