The story of atomic energy is both a tale of incredible discovery by a community of dedicated scientists and a lesson in how to adapt to a powerful new source of energy. In the first 40 years of this century theoretical and experimental physicists probed the atom to understand its secrets. These scientists operated within an international community where bits of knowledge and insight were immediately shared with colleagues. Slowly the outline of the structure of the atom was understood only to discover in an experiment by Otto Hahn in Germany in 1939 that the atom was a potential source of energy. Scientists from all over the world immediately understood the explosive potential of the atom, and many feared going further. This knowledge and the subsequent mobilization of scientists for work on an atomic weapon ended the first phase of the history of atomic energy.
Once governmental authorities in France, Germany, Great Britain, the Soviet Union, and the United States comprehended the potential of atomic energy as a military weapon, the nature of the debate over atomic energy changed dramatically. Suddenly, secrecy was the keynote rather than dissemination of information. In the beginning, this secrecy was self-imposed by scientists themselves, because they feared that German scientists might use the knowledge to give Adolf Hitler a bomb. Soon, however, the governmental agencies imposed secrecy in the interests of national security. Five countries seriously investigated the possibility of building an atomic bomb in the mid-1940s—Germany, Japan, the Soviet Union, the United Kingdom, and the United States. Only the United States, with considerable help from British and German emigrant scientists, was successful in building an atomic bomb in time for use in World War II. The detonation of two atomic bombs on the Japanese cities of Hiroshima and Nagasaki ended the second phase of the history of atomic energy.
The third phase of atomic energy lasted from 1945 to 1960. It was in