|Fig. 1: An image of James Chadwick. (Source: Wikimedia Commons)|
In tandem with the MAUD Report, James Chadwick is one of the most notable men responsible for this report but also has many other attributions to his name. Most remarkably is his discovery of the neutron in 1932, where he won a Nobel Prize in 1935 for his work. In addition, he is known for his role in the Manhattan Project on the British team. His role as a researcher and physicist and the work that he produced throughout his career has profoundly influenced the direction of physics, science, and especially nuclear energy over time.
James Chadwick, seen in Fig. 1, was born to parents John Joseph Chadwick and Anne Mary Knowles in Cheshire, England on October 20th, 1891. For his education, he attended his local High School of Manchester High School and went on to further his education at Manchester University, where he graduated in 1911 from the Honours School of Physics. His next couple of years consisted of working under the famous Professor (later Lord) Rutherford.  Rutherford was one of the leading people in the study of radioactivity and even won a Nobel Prize himself in Chemistry.  He continued to work under prominent names, such as Professor H. Geiger, before the First World War broke out. From there, his work in the domain of nuclear science would become revolutionary.
His work with Geiger did not last long. As a result of the war, Chadwick spent four years in a prison camp; however, that did not stop his scientific curiosity. He worked with as little resources as possible, only having tin foil and a type of chemical toothpaste. After the First World War, he was able to return to Cambridge to complete his PhD. Throughout all of this time, he had before observed the proton and understood that there was something in the nucleus in addition to protons. This observation and study persisted more than a decade with many experiments and combined research with other physicists. One experiment conducted by Frédéric and Irène Joliot-Curie really paved the way for this discovery. This experiment was the way in which radiation knocked loose particles as heavy as protons from the wax target that was hit by beryllium.  Joliot-Curie believed the radiation that was knocking these protons free must be high-energy gamma photons, but Chadwick had an inkling otherwise. His succeeding experiments brought him to the conclusion that this radiation that was being emitted was something about the same size mass of a proton but with neutral charge. Thus, in February of 1932, he released his first paper, titled "The Possible Existence of a Neutron". After more research, he later changed the name to "The Existence of a Neutron". This work is important because of how it contradicts his predecessor, Rutherford's, conclusion of what a neutron was. It was deemed in fact a new particle, rather than the combination of an electron and proton as Rutherford had once suggested.
In the last decade of his career, he served as Master of Gonville and Caius College for a decade, before retiring in 1959. Chadwick's discovery of the neutron first and foremost changed the way scientists did their work. It changed their inherent views on the atom and led to many more substantial projects, such as, the atomic bomb itself. Chadwick got to study and learn under some of the most notable people in the history of scientific discovery: H. G. J. Mosely, Charles Darwin, Kasimir Fajans, and others just to name a few. These people were in fact influential in his own discoveries.  He even, as mentioned above, added to some of their own work, especially that of Rutherford. He passed peacefully in his sleep in 1974.
© Keller Chryst. 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.
 A. Brown, The Neutron and the Bomb: A Biography of Sir James Chadwick (Oxford University Press, 1997).
 P. J. Westwick, "Selected Bibliography," Hist. Stud. Phys. Biol. 28, 353 (1998).
 M. Leone and N. Robotti, "Frédéric Joliot, Irène Curie and the Early History of the Positron (1932-33)," Eur. J. Phys. 31, 975 (2010).