by the use of the atom bomb in Hiroshima, Morrison became a champion of nuclear nonproliferation. He wrote for the Bulletin of the Atomic Scientists, and helped found the Federation of American Scientists and the Institute for Defense and Disarmament Studies. He testified before Congress on the need for civilian control of nuclear energy, and participated in the Civil Rights Congress in New York and the Cultural and Scientific Conference for World Peace in 1949. That year, Life magazine included his image in a gallery of "America's 50 most eminent dupes and fellow travellers". Morrison had joined the Communist Party while he was at Berkeley. The House Un-American Activities Committee devoted four pages of a 1951 report to his activities, and in 1953, he was called before the Senate Internal Security Subcommittee. Theodore Paul Wright, the Acting President of Cornell, was put under great pressure from board members and alumni to fire Morrison, but Bethe remained supportive, and Robert R. Wilson declared that Morrison had "demonstrated his patriotism by the distinguished role he played in the wartime development of the atomic bomb." Deane Malott, who became president of Cornell in 1951, was much less sympathetic, and instructed Morrison to curtail all activities beyond his academic field. Morrison agreed to do so in 1954. Nonetheless, he was one of the few ex-communists to remain employed and academically active throughout the 1950s. In 1999, writer Jeremy Stone alleged that Morrison had been the Soviet spy Perseus, a charge that Morrison strongly and credibly rebutted. Stone accepted his rebuttal. Academic work Morrison co-wrote a paper with Leonard I. Schiff in 1940 in which they calculated the gamma rays emitted by the process of K-electron capture. Initially at Cornell after the war, Morrison continued working in nuclear physics, collaborating with Bethe on a textbook, Elementary Nuclear Theory (1952), one of the early treatments of the relatively new field. Following his political stances, Morrison's attention began drifting towards the stars. In 1954, he published a paper with Bruno Rossi and Stanislaw Olbert in which they explored Enrico Fermi's theory of how cosmic rays travel through the galaxy. Morrison followed this up with a review of theories of the origins of cosmic rays in 1957. A 1958 paper in Nuovo Cimento is considered to mark the birth of gamma ray astronomy. In collaboration with Giuseppe Cocconi, Morrison published a paper in 1959 proposing the potential of