James Chadwick
James Chadwick discovered the neutron and led the British contribution to the atomic bomb. Born near Manchester in 1891 into a poor family — his father ran a laundry — he intended to study mathematics and joined the wrong queue at enrolment, was too shy to correct it, and read physics instead, under Ernest Rutherford. He went to Berlin in 1913 to work with Hans Geiger and was interned as an enemy alien for the whole of the First World War at a racecourse near Berlin, where he and other prisoners improvised a laboratory using materials smuggled in by sympathetic Germans. He returned to Rutherford at Cambridge and spent a decade searching for a neutral particle that Rutherford had postulated in 1920 to explain why atomic masses exceeded the sum of their protons. The evidence came from abroad. Bothe and Becker found that beryllium bombarded with alpha particles emitted a penetrating radiation, and the Joliot-Curies showed in early 1932 that it could knock protons out of paraffin, interpreting it as gamma rays. Chadwick saw that gamma rays could not carry enough momentum. In about three weeks of continuous work in February 1932 he measured the recoil of nuclei of several elements and showed the radiation consisted of neutral particles of roughly a proton's mass. The neutron explained isotopes and, because it is uncharged and can enter a nucleus unrepelled, made fission possible. He received the Nobel Prize in 1935, wrote the MAUD report that convinced Britain and then America a bomb was feasible, and headed the British mission at Los Alamos. He died in 1974.
- Lived: 1891 CE – 1974 CE
- Nationality: British
- Roles: physicist, scientist
