James Chadwick, who is remembered principally for his work in nuclear physics, received the Nobel Prize in 1935 for his discovery of the neutron. That discovery gave rise to new approaches and techniques in the physical sciences, new developments in the biological sciences, and a new form of warfare. Chadwick himself was actively involved with the development of the atomic bomb. Although he was shy and did not have the public visibility of other physicists of his time, his work in science, diplomacy, and administration left permanent marks in twentieth-century history. Knighted in 1945, Chadwick received the Medal of Merit from the United States government in 1946, and the Copley Medal of the Royal Society in 1950.

Chadwick was born in Bollington, not far from Manchester, England, on October 20, 1891, to John Joseph Chadwick and Ann Mary Knowles. Chadwick senior owned a laundry business in Manchester. At the age of sixteen, Chadwick won...