Frank Friedman Oppenheimer (August 14, 1912 – February 3, 1985) was an American particle physicist, cattle rancher, professor of physics at the University of Colorado, and the founder of the Exploratorium in San Francisco. A younger brother of renowned physicist J. Robert Oppenheimer, Frank Oppenheimer conducted research on aspects of nuclear physics during the time of the Manhattan Project, and made contributions to uranium enrichment. After the war, Oppenheimer's earlier involvement with the American Communist Party placed him under scrutiny, and he resigned from his physics position at the University of Minnesota. Oppenheimer was a target of McCarthyism and was blacklisted from finding any physics teaching position in the United States until 1957, when he was allowed to teach science at a high school in Colorado. This rehabilitation allowed him to gain a position at the University of Colorado teaching physics. In 1969, Oppenheimer founded the Exploratorium in San Francisco, and he served as its first director until his death in 1985. Early life and education Frank Friedman Oppenheimer was born in 1912 in New York City to Julius Oppenheimer and Ella Friedman. During his childhood, he studied painting. He also studied the flute under nationally known teacher George Barrera, becoming competent enough at the instrument to consider a career as a flautist. Frank began his schooling at the Ethical Culture School, where he attended until seventh grade. The remainder of his high school education was completed at Fieldston School in Riverdale; a school operated by the Ethical Culture Society. Frank eventually followed the advice of his older brother Robert, and became a professional physicist. He entered into studies at Johns Hopkins University in 1930, graduating three years later with a BS in physics. Afterwards, Frank studied for a year and a half at the Cavendish Laboratory in Cambridge, England, where he also earned a pilot's license. In 1935, he worked on the development of nuclear particle counters at the Institute di Arcetri in Florence, Italy. While completing his PhD work at the California Institute of Technology, Oppenheimer became engaged to Jacquenette Quann, an economics student at the University of California, Berkeley; she was also active in the Young Communist League. In spite of Robert's recommendations, Frank and Jackie were married in 1936 and soon both joined the American Communist Party, also against the older brother's advice. Both Frank and his wife were atheists. Frank Oppenheimer received his PhD in