Fritz Zwicky

Fritz Zwicky (1898–1974) was a Swiss astronomer and physicist, born in Varna, Bulgaria, to Swiss parents, who spent most of his career at the California Institute of Technology and the Mount Wilson and Palomar observatories. Brilliant, prolific, and famously abrasive, he made a string of predictions decades ahead of their confirmation — and was routinely ignored or dismissed in his own time.

In 1933 Zwicky applied the virial theorem to the Coma cluster of galaxies. By measuring the galaxies' velocity dispersion — about 1000 km/s — and estimating the cluster's luminous mass, he found a glaring discrepancy: the visible matter supplied only a small fraction of the gravity needed to keep the fast-moving galaxies bound. He concluded that the cluster must contain far more mass than meets the eye, and named the missing ingredient dunkle Materie — dark matter. The claim sat largely unexamined for forty years until Vera Rubin's rotation curves brought it back.

In 1934, with Walter Baade, Zwicky coined the term 'supernova' and proposed — astonishingly, only two years after the neutron was discovered — that supernovae mark the transition of an ordinary star into a neutron star, releasing enormous energy as gravitational binding energy. The same papers suggested that supernovae are the source of cosmic rays. Both ideas were decades ahead of their acceptance. He also pioneered the use of gravitational lensing by galaxies as a tool, another idea vindicated long after his death.

Zwicky's relationship with his colleagues was legendarily hostile; he dismissed many of them as 'spherical bastards' — bastards, he explained, no matter which way you looked at them. His prickliness, his foreign accent, and the boldness of his claims combined to keep his ideas marginal during his lifetime. History has been far kinder: dark matter, neutron stars, supernovae as their origin, and galaxy lensing are all now central to astrophysics, and all trace to Zwicky in the 1930s.