Albuquerque, New Mexico – In the film “Oppenheimer,” General Leslie Groves questions J. Robert Oppenheimer about the potential catastrophic consequences of pressing the atomic bomb detonation button. This conversation raises the “non-zero” chance that the bomb could ignite a chain reaction in Earth’s atmosphere, a scenario that intrigued nuclear astrophysicists Michael Wiescher and Karlheinz Langanke.
Wiescher and Langanke recently published a paper exploring how Oppenheimer and his colleagues assessed the risk of atmospheric ignition during the early stages of nuclear physics. The research delved into the unexpected benefits discovered in nuclear astrophysics and radiocarbon dating as a result of the Manhattan Project.
The Manhattan Project, led by Oppenheimer at the Los Alamos Laboratory, was a monumental effort that involved numerous renowned scientists and took three years to complete. The project’s massive investment of $2 billion USD at the time led to the employment of over 125,000 individuals, with the main cost being the facilities needed to produce the bomb fuel.
The atomic bomb operates through nuclear fission, a process that splits the nucleus of a radioactive isotope into smaller nuclei by bombarding it with neutrons. During the bomb’s development, Oppenheimer’s major scientific concern was the potential ignition of the atmosphere through fusion reactions, particularly the fusion of hydrogen nuclei and nitrogen-14.
Despite these concerns, experts like Arthur H. Compton and Hans Bethe reassured Oppenheimer that the extreme event of atmospheric ignition was unlikely. Their predictions were confirmed during the Trinity Test in New Mexico, where the plutonium-239 bomb did not ignite the atmosphere.
The development of more powerful nuclear weapons, such as the hydrogen bomb, further advanced understanding of fusion reactions and led to the discovery of unexpected benefits in nuclear astrophysics and radiocarbon dating. The release of neutrons from the bomb triggered reactions that produced long-lived radioactive carbon-14, providing archaeologists with a useful tool for dating organic remains up to about 60,000 years old.
Ultimately, the fear of atmospheric ignition helped propel advancements in nuclear astrophysics, contributing to a better understanding of fusion reactions in stars and the production of heavy elements in the universe. Wiescher emphasized that while there was initial uncertainty, the reliability of the models and assumptions made during the early test program turned out to be quite good in hindsight.