jan 26, 1939 - Discovery of nuclear fission

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In December 1938, over Christmas vacation, physicists Lise Meitner and Otto Frisch made a startling discovery that would immediately revolutionize nuclear physics and lead to the atomic bomb. Trying to explain a puzzling finding made by nuclear chemist Otto Hahn in Berlin, Meitner and Frisch realized that something previously thought impossible was actually happening: that a uranium nucleus had split in two.After the split, the two drops would be driven apart by their mutual electric repulsion at high energy, about 200 MeV, Frisch and Meitner figured. Where would the energy come from? Meitner determined that the two daughter nuclei together would be less massive than the original uranium nucleus by about one-fifth the mass of a proton, which, when plugged into Einstein’s famous formula, E=mc2, works out to 200 MeVMeitner and Frisch sent their paper to Nature in January. Frisch named the new nuclear process "fission" after learning that the term "binary fission" was used by biologists to describe cell division. Hahn and Strassmann published their finding separately, and did not acknowledge Meitner’s role in the discovery.
Scientists quickly recognized that if the fission reaction also emitted enough secondary neutrons, a chain reaction could potentially occur, releasing enormous amounts of energy. Many scientists joined the efforts to produce an atomic bomb, but Meitner wanted no part of that work, and was later greatly saddened by the fact that her discovery had led to such destructive weapons. She did continue her research on nuclear reactions, and contributed to the construction of Sweden's first nuclear reactor. Hahn won the Nobel Prize in chemistry in 1944, but Meitner was never recognized for her important role in the discovery of fission.

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