The German Genius

Hahn, lecturing at Cornell. 45 That left Lise Meitner in charge at the KWI for Chemistry back in Berlin. She was Jewish but Austrian and so, for the time being, did not come under the racial laws. 46 She watched as former colleagues were dismissed or left on their own initiative, including Otto Frisch, her nephew, with whom she had often played piano, who was dismissed from his post in Hamburg, and Leo Szilard, Hungarian-Jewish, who left for England “with his life’s savings hidden in his shoes.” 47 It was to be Szilard, famously, who, when safely in London that September and crossing Southampton Row at some traffic lights, had the idea of a chain reaction, which would be self-sustaining and produce an explosion. (He patented the idea and assigned it to the British Admiralty on condition that it be kept secret.) Meanwhile Enrico Fermi, an Italian physicist based in Rome, had, without knowing it, split the uranium atom, though it was two Germans, Ida and Walter Noddack, at Freiburg-im-Breisgau, who first recognized this.
    In 1936 Hahn and Meitner were nominated for the Nobel Prize by Max Planck, Heisenberg, and Laue, apparently in an attempt to protect their Jewish colleagues. * But when the Anschluss occurred in March 1938, Meitner and Hahn’s protection was removed at a stroke. Carl Bosch, who had worked on the nitrate-fixation process with Haber, managed to get Meitner permission to travel and she went to the Netherlands, with just two suitcases and a diamond ring Hahn had given her so she would have something to sell. 48
    The climax of physics was achieved by these personalities in the run-up to and in the immediate wake of the outbreak of war. In Berlin, Otto Hahn found that if he bombarded uranium with neutrons he repeatedly got barium. In a letter he shared these bewildering results with Meitner, now in exile in Göteborg. As luck would have it, Meitner was visited that Christmas by her nephew Otto Frisch, also in exile, with Bohr in Copenhagen. The pair went cross-country skiing in the woods, which were covered in snow. Meitner told her nephew about Hahn’s letter, and they turned the barium problem over in their minds as they moved between the trees. Until then, physicists had considered that when the nucleus was bombarded, it was so stable that at most the odd particle could be chipped off. Now, huddled on a fallen tree in the Goteburg woods, Meitner and Frisch wondered whether, instead of being chipped away by neutrons, a nucleus could in certain circumstances be cleaved in two.
    They had been in the cold woods for three hours. Nonetheless, they did the calculations before turning for home. What the arithmetic showed was that if the uranium atom did split, as they thought it might, it could produce barium (56 protons) and krypton (36)—56+36=92. As the news sank in around the world, people realized that, as the nucleus split apart, it released energy, as heat. If that energy was in the form of neutrons, and in sufficient quantity, then a chain reaction, and a bomb, might well be possible. But how much U 235 was needed? 49
    The pitiful irony of this predicament was that it was still only early 1939. Hitler’s aggression was growing, but the world was, technically, still at peace. The Hahn/Meitner/Frisch results were published openly in Nature, and thus read by physicists in Nazi Germany, in Soviet Russia, and in Japan, as well as in Britain, France, Italy, and the United States. The problem that now faced the physicists was: how likely was a chain reaction? America, with the greatest resources, and now the home of so many of the exiles, was a nonbelligerent after war broke out in Europe. How could she be persuaded to act? It was only after Frisch and Rudolf Peierls, two German exiles now working at the University of Birmingham in England, and walking the blacked-out streets of the city at night, calculated (in a three-page paper), that about one kilogram of uranium was sufficient (as opposed to 13–40 tons, according to earlier calculations), that movement began. 50 Mark Oliphant, Frisch and Peierls’s professor at Birmingham, traveled to America and persuaded the Americans to explore whether a bomb could be built. Without informing Congress, President Roosevelt, motivated by a letter from Einstein (drafted by Szilard) found the money “from a special source available for such an unusual purpose.” Thus German-Jewish physicists played a full role in bringing into existence the bomb that would