He worked most of his life at the California Institute of Technology in the United States of America, where he made many important contributions in theoretical and observational astronomy.

[2] In 1933, Zwicky was the first to use the virial theorem to postulate the existence of unseen dark matter, describing it as "dunkle Materie".

[3][4] Fritz Zwicky was born in Varna, Bulgaria, to a Swiss father (citizenship in Mollis, Glarus[5]) and Czech mother.

He received an advanced education in mathematics and experimental physics at the Swiss Federal Polytechnic (today known as ETH Zurich) in Zürich.

[5] In 1925, Zwicky emigrated to the United States to work with Robert Millikan at California Institute of Technology (Caltech) after receiving the Rockefeller Foundation fellowship.

[8] Zwicky developed numerous cosmological theories that have had a profound influence on the understanding of our universe in the early 21st century.

[16] The Fritz Zwicky Stiftung (Foundation) was established in Switzerland to carry on his ideas relating to "Morphological analysis".

Zwicky did his laborious work, comparing photographic plates with the human eye, which is far more challenging and difficult than Boles accomplished using modern technology for his record.

[22] While examining the Coma galaxy cluster in 1933, Zwicky was the first to use the virial theorem to discover the existence of a gravitational anomaly, which he termed dunkle Materie 'dark matter'.

He calculated the gravitational mass of the galaxies within the cluster from the observed rotational velocities and obtained a value at least 400 times greater than expected from their luminosity.

He proposed that the reddening effect was not due to motions of the galaxy, but to an unknown phenomenon that caused photons to lose energy as they traveled through space.

It was not until 1956 that Walter Baade corrected the distance scale based on Cepheid variable stars, and ushered in the first accurate measures of the expansion rate.

[27] Zwicky developed a generalised form of morphological analysis, which is a method for systematically structuring and investigating the total set of relationships contained in multi-dimensional, usually non-quantifiable, problem complexes.

[31] Zwicky with his wife Margaritha also produced an important catalog of compact galaxies, sometimes called simply The Red Book.

An anecdote often told of Zwicky concerns an informal experiment to see if he could reduce problems with turbulence hindering an observation session one night at Mount Wilson observatory.

[34] In a talk to a Caltech PhD student Frank Malina, who experienced some difficulties working on a dissertation regarding characteristics of oxygen-gasoline rocket engine, Fritz Zwicky claimed the engineer "must realize that a rocket could not operate in space as it required the atmosphere to push against to provide thrust".

Twelve days later, on October 16, 1957, Zwicky launched his experiment on the Aerobee, and successfully fired pellets visible from the Mount Palomar observatory.

He considered this might be achieved by firing pellets into the Sun to produce asymmetrical fusion explosions, and by this means he thought that the star Alpha Centauri might be reached within 2500 years.

These two sides of his nature came together in the aftermath of the Second World War, when Zwicky worked hard to collect tons of books on astronomy and other topics, and shipped them to war-ravaged scientific libraries in Europe and Asia.

He considered that hope for the world lay with free people of good will who work together as needed, without institutions or permanent organizations.

In 1934 he was featured in Literary Digest's "They Stand Out from the Crowd" column, ... and in 1935 he gave a Science Service Radio Talk titled "Stellar Guests".