EMILIO SEGRE VISUAL ARCHIVES / AMERICAN INSTITUTE OF PHYSICS / SCIENCE PHOTO LIBRARY EMILIO SEGRE VISUAL ARCHIVES / AMERICAN INSTITUTE OF PHYSICS / SCIENCE PHOTO LIBRARY
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John Cockcroft (1897-1967). Portrait of the British physicist John Cockcroft. In 1932, Cockcroft performed the first artificial disintegration of an atomic nucleus. He bombarded a lithium nucleus with protons in a particle accelerator, and observed two alpha particles (helium nuclei) being produced. Study of the energies of these particles verified Einstein's theory of mass-energy equivalence. He was awarded the 1951 Nobel Prize for Physics for this work, along with Ernest Walton. Photographed in 1951.
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