Otto Hahn

Otto Hahn is identified as one of the two German chemists whose demonstration of uranium fission reached J. Robert Oppenheimer in January 1939. The book presents Hahn chiefly through this discovery: a reported laboratory result that Oppenheimer initially rejected, then quickly recognized as a development with implications for both nuclear power and bombs.

Identification and Appearance

On Sunday, January 29, 1939, physicist Luis W. Alvarez read a wire-service report in the San Francisco Chronicle stating that Hahn and Fritz Strassmann had split uranium nuclei by bombarding uranium with neutrons. The account describes uranium as one of the heaviest elements and explains that its nucleus could be divided into two or more parts. Hahn’s presence in the narrative is thus tied to a specific scientific result, not to a developed personal portrait or an encounter with Oppenheimer.

From Report to Confirmation

Alvarez hurried to the Radiation Laboratory to share the news with Oppenheimer, who initially considered the result impossible and tried to show mathematically that fission could not occur. The next day, Alvarez repeated the experiment in his laboratory. He showed Oppenheimer the small natural alpha-particle pulses and the much taller fission pulses—twenty-five times larger. Oppenheimer accepted the reaction as authentic within minutes.

Significance of the Discovery

Once convinced, Oppenheimer rapidly considered what the result might make possible: extra neutrons released during fission could split further uranium atoms, yielding power or bombs. That inference belongs to Oppenheimer’s response to the discovery; the narrative identifies Hahn and Strassmann as the chemists who demonstrated the splitting of uranium. The contrast between the initial rejection and the swift reconsideration gives Hahn’s brief appearance its significance: his reported result marks the point at which an unfamiliar phenomenon became, for Oppenheimer, an urgent practical possibility.