The Remarkable Discoveries of Fritz Zwicky


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Fritz Zwicky. Image courtesy of Mythack

Fritz Zwicky was born in 1898. Image courtesy of Mythack

Fritz Zwicky was the first astronomer to propose the existence of dark matter, supernovas, neutron stars, galactic cosmic rays, gravitational lensing by galaxies, and galaxy clusters. However, his peers generally ignored his predictions and observations. He has been called “the most unrecognized genius of twentieth century astronomy” by many, and remains virtually unknown to the public to this day.

Fritz Zwicky: The Early Years 

Born in Bulgaria in 1898 to a Swiss father and Czech mother, Fritz Zwicky was sent to his grandparents in Switzerland to study commerce at age six. His interests soon turned to physics, and in 1916 he enrolled in Zurich Polytechnic Institute — the same college Albert Einstein attended twenty years earlier — earning his Doctorate in 1922.

Zwicky came to the U.S. in 1925  to work for Robert Millikan at the California Institute of Technology (Caltech). There, he began his collaboration with fellow German-speaking observational astronomer Walter Baade.

Astronomy Genius: Cosmic Predictions

In 1933, Zwicky proposed galaxies harbor huge quantities of unseen matter. Based on the motion of outlying galaxies in the Coma galaxy cluster, Zwicky concluded there was not enough visible matter to hold these fast-moving galaxies together. He insisted something invisible was producing additional gravity out there in the heavens. Zwicky dubbed this still unknown substance dark matter.

The Crab Nebula – Remnant from supernova visible in the sky in 1054 A.D. Neutron star is at its center. NASA Image by Chandra.

Three years earlier, nineteen-year-old Indian physicist Subrahmanyan Chandrasekhar predicted that if a dying star’s collapsed core had a mass greater than about 1.4 times the mass of the Sun, it would overcome all electron forces, and continue to collapse. In 1933, Zwicky and Baade proposed the existence of just such a collapsed core — a neutron star.

From the discovery of the neutron just a year earlier, Zwicky proposed that when a massive star runs out of fuel at the end of its life, its core is compressed by the star’s tremendous gravity to such an extreme degree that a large portion of its electrons and protons squeeze together to form neutrons. (Neutrons are particles with neutral electric charge found in the nucleus of atoms.) The result is a super-dense neutron star some 10 to 20 miles in diameter, yet 1.4X more massive than the Sun. To illustrate the concept, a single teaspoon of neutron star material weighs about 10 million tons.

Zwicky and Baade also proposed this star-core-implosion powered a massive explosion of the star’s outer layers. Zwicky dubbed it a supernova. During flare-ups, these super-bright objects can be nearly 10 billion times more luminous than the Sun. Zwicky also predicted supernova explosions produce galactic cosmic rays — high energy subatomic particles traveling at nearly the speed of light.

Physicist Kip Thorne later called the 1934 Zwicky-Baade paper on supernovas, neutron stars and cosmic rays “one of the most prescient documents in the history of physics and astronomy.

Zwicky’s Caustic Reputation

Stars made of neutrons? Unseen dark matter? Galactic cosmic ray? Astronomers at the time generally thought these extravagant claims were just another bunch of wacky ideas from Zwicky. As British/American physicist Freeman Dyson put it: Fritz Zwicky’s radical ideas and pugnacious personality brought him into frequent conflict with his colleagues at Caltech. They considered him crazy and he considered them stupid.

Zwicky has been called prickly, arrogant, abrasive, and always ready to fight. According to astronomer Jesse Greenstein, he even came in conflict with Baade. During WWII, Greenstein says, “Zwicky called Baade a Nazi, which he wasn’t, and Baade said he was afraid Zwicky would kill him.” In his introduction to a self-published catalogue of compact galaxies in 1971, Zwicky described his colleagues as “scatterbrains, sycophants, and plain thieves . . . (who) doctor their observational data to hide their shortcomings . . . (and publish) useless trash in the bulging astronomical journals.”

Zwicky was first to discover galaxies form in clusters – small portion of Coma Galaxy Cluster shown here. NASA Image by Hubble.

In defense of her father, Zwicky’s youngest daughter, Barbarina told Decoded Science:

My father encountered terrible hostility to his work during his lifetime . . . Freeman Dyson did not know or ever meet my father, and is only repeating the incessant inflammatory anecdotes for his own purposes. The continued opinions of imbeciles are repeated from the oral histories as if they hold some kind of truth, and find their genesis in the inferior minds and failure of my father’s colleagues.”

Astronomy Theories Vindicated

Over the years, nearly all of Zwicky’s theories have been verified. In the early 1970’s, American astronomer Vera Rubin (along with W.K. Ford and others) confirmed Zwicky’s dark matter findings. A number of independent observations now tell us this mysterious dark matter is the most widespread form of matter in the universe — some five times more prevalent than ordinary matter.

Zwicky himself found 129 supernovae — a personal record which still stands. The first of some 1000 known neutron stars in our galaxy were discovered by radio astronomers in the mid-1960’s. And astrophysicists now believe that most galactic cosmic rays come from supernova explosions, just as Zwicky predicted.

Zwicky’s Career and Honors

Gravitational lensing – distant galaxies distorted into giant rings around foreground galaxy, as predicted by Zwicky. NASA Image.

Over his long career, Zwicky wrote some 300 articles, was awarded over 50 patents, and published 10 books. He has been called the “father” of the jet engine, for his work in the 1940’s as Director of Research at Aerojet Engineering Corporation. Zwicky was awarded the Presidential Medal of Freedom by Truman in the 1940’s for his rocket propulsion work during WWII, and he also received the Gold Medal of Britain’s Royal Astronomical Society.

After WWII, Zwicky collected and donated 15 tons of scientific books and journals to war-ravaged scientific libraries in Europe and Asia. He also directed the Pestalozzi Foundation of America, supporting orphanages around the world.

Fritz Zwicky died in Pasadena Feb. 8, 1974, just shy of his 76th birthday. The first gravitational lens was discovered five years later, confirming yet another of his theories.

Asteroid 1803 Zwicky and lunar crater Zwicky are named in his honor.


Swedish Morphological Society. Fritz Zwicky. (2003-2012). Accessed July 2, 2012.

Panec, R. The Father of Dark Matter Still Gets No Respect. (2009). Discover Magazine. Accessed July 2, 2012.

Soter, Steven and deGrasse Tyson, Neil, eds. Fritz Zwicky’s Extraordinary Vision. (2000). American Museum of Natural History. Accessed July 2, 2012.

Maurer, S. M. Idea Man. Beam Line. Accessed July 2, 2012.

Krill, O. Supernovae, an alpine climb and space travel. (1998). Dynamical Systems. Accessed July 2, 2012.

Thorne, K. Black Holes & Time Warps, Einstein’s Outrageous Legacy. (1994). Norton.

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