<P> In the first decades of the 20th century, physics was revolutionised with developments in the understanding of the nature of atoms . In 1898, Pierre and Marie Curie discovered that pitchblende, an ore of uranium, contained a substance--which they named radium--that emitted large amounts of radioactivity . Ernest Rutherford and Frederick Soddy identified that atoms were breaking down and turning into different elements . Hopes were raised among scientists and laymen that the elements around us could contain tremendous amounts of unseen energy, waiting to be harnessed . </P> <P> H.G. Wells was inspired to write about atomic weapons in a 1914 novel, The World Set Free, which appeared shortly before the First World War . In a 1924 article, Winston Churchill speculated about the possible military implications: "Might not a bomb no bigger than an orange be found to possess a secret power to destroy a whole block of buildings--nay to concentrate the force of a thousand tons of cordite and blast a township at a stroke?" </P> <P> In January 1933, Adolf Hitler was appointed Chancellor of Germany and it quickly became unsafe for Jewish scientists to remain in the country . Leó Szilárd fled to London where he proposed, and in 1934 patented, the idea of a nuclear chain reaction via neutrons . The patent also introduced the term critical mass to describe the minimum amount of material required to sustain the chain reaction and its potential to cause an explosion . (British patent 630,726 .) He subsequently assigned the patent to the British Admiralty so that it could be covered by the Official Secrets Act . In a very real sense, Szilárd was the father of the atomic bomb academically . Also in 1934, Irène and Frédéric Joliot - Curie discovered that artificial radioactivity could be induced in stable elements by bombarding them with alpha particles; Enrico Fermi reported similar results when bombarding uranium with neutrons . </P> <P> In December 1938, Otto Hahn and Fritz Strassmann sent a manuscript to Naturwissenschaften reporting that they had detected the element barium after bombarding uranium with neutrons . Lise Meitner and her nephew Otto Robert Frisch correctly interpreted these results as being due to the splitting of the uranium atom . (Frisch confirmed this experimentally on January 13, 1939 .) They gave the process the name "fission" because of its similarity to the splitting of a cell into two new cells . Even before it was published, news of Meitner's and Frisch's interpretation crossed the Atlantic . Scientists at Columbia University decided to replicate the experiment and on January 25, 1939, conducted the first nuclear fission experiment in the United States in the basement of Pupin Hall . The following year, they identified the active component of uranium as being the rare isotope uranium - 235 . </P>

Who came up with the idea of an atomic bomb