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| Fig. 1: James Chadwick (Source: Wikimedia Commons) |
James Chadwick was born on October 20, 1891 to Anne Mary Knowles and John Joseph Chadwick in Cheshire, England (See Fig. 1). [1] He was born into a poor family, with his father working in the cotton industry. At the age of 4, James and his family moved from Cheshire to Manchester in search of work for his father. Despite their move to Manchester, the Chadwick's financial challenges did not cease. As a result, James was sent to live with his grandparents for many years. One of Chadwick's teachers took particular interest in him and helped him apply to college. Chadwick ultimately chose to study at Manchester University, where he worked under Ernest Rutherford. This is where his presence in the world of physics started. Chadwick graduated from Manchester University in 1911 and then went on a fellowhip to Berlin to work with Hans Geiger on beta radiation. He was in Germany when WWI broke out. He was sent to the Ruhlebel Internment Camp and remained there for the duration of the war. [2]
James Chadwick proved the existence of neutrons in 1932. [2] This discovery came from his theory that there was a neutron that accounted for the discrepancies found with the protons and electron atomic number and mass. Around the same time, Irene and Frederic Joliot-Curie were also conducting similar experiments but thought that the reaction was caused by γ rays. Chadwick followed their experiments but came to the different conclusion that the reaction was not an product of γ rays but of neutrons. He recreated the Joliot-Curie experiment with the element beryllium in 1932 and published his research 3 weeks later with his discovery of the neutron. [3] His publication reported the mass of a neutron as 1.008701 amu and the mass of a proton as 1.007316 amu. [4] Today, scientists still believe in the work he did and accept his theories of the neutron.
James Chadwick was awarded a Nobel prize in 1935 for his discovery of the neutron. His discovery of the neutron had tremendous impact on the academic study of astrophysics. Scientists like Walther Baade and Fritz Zwicky and their discovery of the supernova and Jocelyn Bell and Anthony Hewish and their discovery of radio pulse emission from a distant object are a few examples of the impact Chadwick's discovery has had on modern scholarship. [2]
© Zach Sehgal. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] A. Brown, The Neutron and the Bomb: A Biography of Sir James Chadwick (Oxford University Press, 1997).
[2] J. D. Rogers, "The Neutron's Discovery - 80 Years On," Physics Procedia 43, 1 (2013).
[3] J. Chadwick, "The Existence of a Neutron," Proc. R. Soc. Lond A 136, 692 (1932).
[4] M. Kuppermann, "James Chadwick: The Man Behind the Neutron, Physics 241, Stanford University, Winter 2018.
