Nicholas Kemmer was a theoretical physicist whose most famous contribution to science was the prediction in 1938 of the existence of three kinds of particle—one positive, one negative and one neutral—coupled to protons and neutrons in a symmetrical way so as to produce nuclear forces independent of charge. Three particle species were discovered experimentally 10 years later and found to have the nuclear couplings specified by Kemmer. They are the particles now known as π mesons or pions. Other sets of three species with the same symmetry were discovered later. The long interval between prediction and verification was caused by World War I, which interrupted the progress of particle physics in general and Kemmer’s career in particular. After the war he devoted his life to teaching rather than research, and became a beloved mentor and friend to several generations of younger physicists. Among the scientists that he launched into successful research careers are Abdus Salam FRS (Nobel laureate), Paul Matthews FRS, Richard Dalitz FRS and the present writer. In the American Mathematical Society Mathematical Genealogy Project, which includes physicists as well as mathematicians, Kemmer is academic ancestor to 217 descendants.
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