Fritz Zwicky
(1898-1974)
Fritz Zwicky was a most innovative astrophysicist who saw strange possibilities for astronomical objects in his years at Cal Tech.
In 1934, working with his Cal Tech colleague
Walter Baade, Zwicky imagined exploding stars that could throw off most of their matter, but crush their cores to form tiny stars made entirely of neutrons. He and his colleague Zwicky and Baade called such an exploding star a "supernova."
Using measures of the radial velocities of galaxies in the great Coma cluster of galaxies, Zwicky estimated the total kinetic energy T of the cluster. By the virial theorem, T should equal to minus 1/2 times the total gravitational potential energy V. The potential energy must equal twice the kinetic energy. But Zwicky found there is not enough observable matter to provide the gravitational potential energy V needed to satisfy the virial theorem. Zwicky was thus the first to infer the existence of unseen dark matter that he called "dunkle Materie."
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