Meitner and Frisch Explain Nuclear Fission
A uranium atom splits in Berlin, and physicists in exile are the ones who work out why
Quick facts
- Experimental discovery
- Otto Hahn, Fritz Strassmann, December 1938, Berlin
- Theoretical explanation
- Lise Meitner, Otto Frisch
- Published
- Nature, February 1939
- Nobel recognition
- 1944 Nobel Prize in Chemistry, Hahn only
What happened
In December 1938 in Berlin, chemists Otto Hahn and Fritz Strassmann bombarded uranium with neutrons and found what looked like barium among the products, a baffling result since barium is roughly half the mass of uranium. The U.S. National Park Service's account of the discovery notes that Hahn achieved nuclear fission during an experiment but did not realize it, and asked Meitner for help in explaining his puzzling results. Lise Meitner, a physicist who had fled Nazi Germany for Sweden earlier that year because she was Jewish, worked out the answer with her nephew, physicist Otto Frisch: the uranium nucleus was splitting into two lighter nuclei, releasing enormous energy in the process. The National Park Service credits the pair directly: Meitner and Frisch were the first to call the process fission, and in 1939 they published a scientific paper explaining the process, appearing in the journal Nature in February 1939.
Why it matters
The discovery of fission showed that splitting a heavy atomic nucleus released far more energy than any known chemical reaction, a fact that made both nuclear power and nuclear weapons physically possible within years. Otto Hahn alone received the 1944 Nobel Prize in Chemistry for the discovery; Meitner, who provided the theoretical explanation and had done nuclear research with Hahn for three decades, was left off the prize entirely, a case widely cited today as one of the starkest omissions in Nobel Prize history.
How we know
Hahn and Strassmann published their puzzling experimental results in Naturwissenschaften in January 1939, and Meitner and Frisch's theoretical explanation appeared in Nature the following month; both papers survive in the scientific literature and are corroborated by Meitner's correspondence with Hahn from the same weeks, held in archival collections and quoted directly in National Park Service historical materials.
Sources
- U.S. National Park Service. B Reactor History Room: Nuclear Fission · Primary source (author-declared)nps.gov · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
- U.S. National Park Service. Women of the Manhattan Project: Lise Meitner · Primary source (author-declared)nps.gov · Cited as a "primary" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
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