Discovery of nuclear fission
- Date
- December 1938 (explained January–February 1939)
- Category
- Science, technology & invention
- Region
- Europe (Germany / Sweden)
- Era
- Modern
- Significance
In December 1938, chemists Otto Hahn and Fritz Strassmann in Berlin, bombarding uranium with neutrons, identified barium among the products — evidence that the uranium nucleus had split, a result they confirmed on 19 December 1938.
Lise Meitner, who had recently fled Nazi Germany, and her nephew Otto Frisch provided the theoretical explanation over the Christmas holiday, modelling the nucleus as a splitting liquid drop and estimating the enormous energy released; their interpretation was published in February 1939, and Frisch coined the term 'fission'. The discovery revealed that splitting heavy nuclei liberates large amounts of energy and can release additional neutrons, raising the possibility of a self-sustaining chain reaction. This insight directly motivated wartime nuclear research, including the Manhattan Project, and led to both nuclear weapons and civilian nuclear power. The discovery thus stands as one of the most consequential scientific findings of the century, reshaping international security and energy in the decades that followed.
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Empires active in December 1938 (explained January–February 1939)
- Soviet Union1922 CE – 1991 CE
- Empire of Japan1868 CE – 1947 CE
- French Colonial Empire (Second)1830 CE – 1962 CE
- British Empire1583 CE – 1997 CE
- Spanish Empire1492 CE – 1976 CE
- Portuguese Empire1415 CE – 1999 CE
Related science, technology & invention events
- Penicillin and the dawn of the antibiotic era1928 (developed for clinical use 1940–1945)
- Formulation of quantum mechanics1925–1927
- Haber-Bosch Process Industrialises Synthetic Nitrogen FertiliserSeptember 1913
- The Wright Brothers' Powered Flight17 December 1903
- Discovery of X-rays and radioactivity1895–1898
- Germ Theory of Disease Established by Pasteur and Koch1882 (Koch's tuberculosis bacillus, 24 March)
Further reading
The wider story
A Little History of Science
Warm, jargon-free tour of discovery from Babylonian stargazers to the genome.
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