|Oppenheimer (ŏp'ən-hī'mər) Pronunciation Key
American physicist who directed the Los Alamos, New Mexico, laboratory during the development of the first atomic bomb (1942-1945). After World War II, he became an advocate for the peaceful use of atomic energy and opposed the development of the hydrogen bomb.
Note: In the early 1950s, Oppenheimer's opposition to building the hydrogen bomb and his past association with leftists led to a hearing regarding his security clearance. Although the committee found that he was a “loyal citizen,” his security clearance was not restored, and he was barred from government research. Oppenheimer's chief opponent in the scientific community at this time was Edward Teller.