# Fritz Zwicky

> Swiss astronomer who posited dark matter (1898–1974)

**Wikidata**: [Q115462](https://www.wikidata.org/wiki/Q115462)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Fritz_Zwicky)  
**Source**: https://4ort.xyz/entity/fritz-zwicky

## Summary

Fritz Zwicky was born on February 14, 1898, in Varna [1][2][3][4][5][6][7][8] and died on February 8, 1974, in Pasadena [1][2][3][4][5][6][9][10][11]. He worked as an astronomer, physicist, university teacher, and astrophysicist [12][13], earning his education at ETH Zurich [14]. Zwicky was employed by the California Institute of Technology from 1927 to 1968 [15][14], where his research focused on astrophysics .He received numerous accolades, including the Gold Medal of the Royal Astronomical Society, the Medal of Freedom, and recognition as a Fellow of the American Physical Society [14][16][17][18][19]. Zwicky was also inducted into the International Space Hall of Fame [14][16][17][18][19] and was a member of the American Physical Society [20]. He is buried in Mollis [21].

## Summary

Fritz Zwicky (1898–1974) was a Swiss astronomer and astrophysicist who pioneered groundbreaking research in extragalactic astronomy and became the first scientist to propose the existence of dark matter. Working primarily at the California Institute of Technology, Zwicky discovered numerous galaxy clusters, developed methods for estimating their masses, and famously calculated that visible matter accounted for only a small fraction of the universe's total mass. His work fundamentally transformed our understanding of cosmic composition and laid the foundation for one of modern cosmology's greatest mysteries.

## Biography

- **Born**: February 14, 1898, in Varna, Bulgaria
- **Died**: February 8, 1974, in Pasadena, California, USA
- **Nationality**: Swiss (citizenship: Switzerland)
- **Education**: ETH Zurich (PhD/degree completed)
- **Known for**: First proposal of dark matter in the universe; discovery of galaxy clusters; supernova classification
- **Employer(s)**: California Institute of Technology (Caltech), ETH Zurich
- **Field(s)**: Astronomy, Astrophysics, Physics, University Teaching

## Contributions

Fritz Zwicky made numerous significant contributions to astronomy and astrophysics throughout his career:

1. **Dark Matter Hypothesis (1933)**: While studying the Coma galaxy cluster, Zwicky calculated the total mass of the cluster based on the velocities of its member galaxies. He found that the mass required to keep the cluster gravitationally bound was far greater than the mass visible in stars and gas. He coined the term "dark matter" (originally "dunkle Materie" in German) to describe this invisible substance, estimating it constituted about 90% of the universe's mass.

2. **Galaxy Cluster Discovery**: Zwicky discovered over 120 galaxy clusters and was instrumental in cataloguing them. His work with Fritz Hermann and others led to the identification of the Zwicky catalog of galaxies and clusters.

3. **Supernova Classification**: He developed a classification system for supernovae and discovered or co-discovered numerous supernovae, contributing to the understanding of stellar death and the creation of neutron stars.

4. **Palomar Observatory Work**: At Caltech's Palomar Observatory, Zwicky conducted extensive surveys of the night sky, photographing thousands of galaxies and documenting their properties.

5. **Morphological Classification**: He developed morphological classification systems for galaxies that contributed to the later Hubble sequence.

6. **Jet Propulsion Laboratory**: During World War II, Zwicky worked at the Jet Propulsion Laboratory (then part of Caltech) on rocket propulsion research.

7. **Publications**: Authored numerous scientific papers and books, including works on galaxies, supernovae, and cosmology.

## FAQs

**What did Fritz Zwicky discover about the universe?**

Fritz Zwicky discovered that the visible matter in galaxy clusters was insufficient to account for their gravitational binding, leading him to propose the existence of dark matter in 1933. This revolutionary hypothesis suggested that most of the universe's mass was invisible—a concept that took decades to gain widespread acceptance.

**Where did Fritz Zwicky work?**

Zwicky worked primarily at the California Institute of Technology (Caltech) in Pasadena, California, where he had access to the Palomar Observatory. He was also affiliated with ETH Zurich in Switzerland, his alma mater, and served as a member of the American Physical Society.

**What awards did Fritz Zwicky receive?**

Zwicky received several prestigious honors, including the Gold Medal of the Royal Astronomical Society and the Medal of Freedom (awarded by the United States government between 1945–1961). The European Astronomical Society established the Fritz Zwicky Prize for Astrophysics and Cosmology in his honor in 2020.

**What is the Zwicky Prize?**

The Fritz Zwicky Prize for Astrophysics and Cosmology is awarded by the European Astronomical Society, named in honor of Fritz Zwicky. It was established in 2020 to recognize outstanding contributions to astrophysics and cosmology.

**What is named after Fritz Zwicky?**

Several astronomical features bear Zwicky's name: the Zwicky lunar impact crater (Zwicky), the Zwicky catalog of galaxies and galaxy clusters, and the Fritz Zwicky Prize. Additionally, the asteroid 1803 Zwicky and the Zwicky Transient Facility at Palomar Observatory honor his contributions to astronomy.

## Why They Matter

Fritz Zwicky's proposal of dark matter fundamentally changed cosmology and remains one of the most significant unsolved problems in physics today. His work in the 1930s was initially met with skepticism, but subsequent observations—including galactic rotation curves by Vera Rubin in the 1970s and gravitational lensing studies—confirmed that dark matter constitutes approximately 27% of the universe's mass-energy content. Without Zwicky's pioneering observations and theoretical work, the existence of dark matter might not have been discovered for decades longer. His methodological approach to estimating cluster masses through velocity dispersion also established foundational techniques still used in extragalactic astronomy. The ongoing search for dark matter particles represents one of the most active areas of astrophysical research, and Zwicky's name remains permanently associated with this cosmic mystery.

## Notable For

- First scientist to propose the existence of dark matter (1933)
- Discovered over 120 galaxy clusters
- Developed supernova classification system
- Recipient of the Gold Medal of the Royal Astronomical Society
- Recipient of the Medal of Freedom (United States)
- Namesake of the Zwicky lunar crater
- Namesake of the Fritz Zwicky Prize for Astrophysics and Cosmology (established 2020)
- ETH Zurich alumnus and Caltech professor
- Member of the American Physical Society

## Body

### Early Life and Education

Fritz Zwicky was born on February 14, 1898, in Varna, Bulgaria, to Swiss parents. His father was an accountant who had moved to Bulgaria for work. In 1904, the family returned to Switzerland, and Zwicky pursued his education in the Swiss system. He attended ETH Zurich (Eidgenössische Technische Hochschule Zürich), one of Europe's premier technical universities, where he completed his doctoral studies. ETH Zurich, founded in 1855, would remain an important affiliation throughout his career.

### Academic Career and Affiliations

Zwicky spent the majority of his professional career at the California Institute of Technology (Caltech) in Pasadena, California. Caltech, founded in 1891, is a private research university renowned for its strength in science and engineering. At Caltech, Zwicky had access to the Palomar Observatory, one of the world's most important astronomical facilities. He also maintained connections to his alma mater, ETH Zurich, and was a member of the American Physical Society, an organization founded in 1899.

### Dark Matter Discovery

The most significant contribution of Fritz Zwicky's career came in 1933 while studying the Coma galaxy cluster. Using the virial theorem to estimate the cluster's total mass based on the velocities of its member galaxies, Zwicky calculated that the cluster's mass was approximately 400 times greater than could be accounted for by visible matter alone. He concluded that a large portion of the universe must consist of "dark matter"—non-luminous material that exerts gravitational influence but does not emit or absorb light. This hypothesis, radical for its time, has been confirmed by numerous subsequent observations and remains one of the biggest mysteries in modern physics.

### Galaxy Cluster Research

Zwicky was a prolific discoverer of galaxy clusters, identifying over 120 clusters during his career. He worked to systematically catalog and classify these massive cosmic structures, developing methods for estimating their masses and studying their properties. His work contributed significantly to understanding the large-scale structure of the universe. The Zwicky catalog of galaxies and galaxy clusters remains an important reference in extragalactic astronomy.

### Supernova Research

Zwicky made substantial contributions to the study of supernovae—powerful stellar explosions that mark the death of massive stars. He developed classification schemes for supernovae and discovered or co-discovered numerous examples. His work helped establish supernovae as standard candles for measuring cosmic distances and contributed to the understanding of stellar evolution and the creation of neutron stars.

### World War II and Applied Research

During World War II, Zwicky contributed to the war effort through his work at the Jet Propulsion Laboratory (JPL), which was then operated by Caltech for the U.S. government. JPL, founded in 1936, later became NASA's primary center for robotic planetary exploration. Zwicky worked on rocket propulsion research during this period.

### Honors and Legacy

Zwicky received numerous honors for his contributions to astronomy and physics. He was awarded the Gold Medal of the Royal Astronomical Society, one of the most prestigious awards in astronomy, and the Medal of Freedom by the United States government. His legacy continues through the Fritz Zwicky Prize for Astrophysics and Cosmology, established by the European Astronomical Society in 2020. The lunar crater Zwicky bears his name, as does asteroid 1803 Zwicky. The Zwicky Transient Facility at Palomar Observatory continues his tradition of astronomical discovery.

### Personal Characteristics

Zwicky was known for his prolific output and sometimes contentious personality. He was a prolific writer and speaker who was not afraid to challenge prevailing scientific orthodoxies. Despite his Swiss citizenship, he spent much of his career in the United States at Caltech, where he became a central figure in the development of American extragalactic astronomy.

### Death and Posthumous Recognition

Fritz Zwicky died on February 8, 1974, in Pasadena, California, just six days before his 76th birthday. His contributions to astronomy have been recognized posthumously through the establishment of awards, the naming of astronomical features, and the continued relevance of his dark matter hypothesis to modern cosmology. The search for dark matter particles remains one of the most important endeavors in astrophysics, with experiments like the Large Hadron Collider and deep underground detectors seeking to directly detect the invisible substance Zwicky first proposed over 90 years ago.

## References

1. [Two fishes in the starry sea : deep-sky delights](http://reference.sabinet.co.za/webx/access/electronic_journals/mnassa/mnassa_v72_n7_10_a16.pdf)
2. [Editorial note to: F. Zwicky The redshift of extragalactic nebulae](http://link.springer.com/content/pdf/10.1007%2Fs10714-008-0706-5.pdf)
3. [Energy content of propellants and of explosives](http://link.springer.com/article/10.1007%2FBF02160838)
4. [Intergalactic matter](http://link.springer.com/article/10.1007%2FBF02154098)
5. MacTutor History of Mathematics archive
6. [Advancing through a decade. 2009](http://news.bbc.co.uk/nolpda/ukfs_news/hi/newsid_8435000/8435246.stm)
7. [Mine to shed light on dark matter mystery. 2009](http://www.theage.com.au/world/mine-to-shed-light-on-dark-matter-mystery-20091220-l7e9.html)
8. [Source](https://zwickymeeting.astro.phys.ethz.ch/zwicky.php)
9. Find a Grave
10. [The Gold Medal. Royal Astronomical Society](https://www.ras.ac.uk/sites/default/files/2023-04/Gold%20Medal%202023.pdf)
11. [Fritz Zwicky. MacTutor History of Mathematics archive](https://mathshistory.st-andrews.ac.uk/Biographies/Zwicky/)
12. [Fritz Zwicky. New Mexico Museum of Space History](https://www.nmspacemuseum.org/inductee/fritz-zwicky/)
13. [Space Pioneers Enshrined. Las Vegas Optic. 1976](https://www.newspapers.com/clip/29967024/las_vegas_optic/)
14. Virtual International Authority File
15. Fritz Zwicky. NNDB
16. [Zwicky, Fritz (1898-1974): Astrophysiker: Veröffentlichte Arbeiten und einzelne Briefe (Bestand). ETH Zurich University Archives](https://vls.hsa.ethz.ch/client/link/de/archiv/einheit/142c9a9d5d83486b8ab64dfd66afc1dd)
17. Encyclopædia Britannica Online
18. SNAC
19. Brockhaus Enzyklopädie
20. Great Norwegian Encyclopedia
21. BnF authorities
22. Gran Enciclopèdia Catalana
23. Croatian Encyclopedia
24. Freebase Data Dumps. 2013
25. Integrated Authority File
26. Historical Dictionary of Switzerland
27. nobelprize.org
28. IdRef
29. CONOR.SI
30. Quora
31. Catalogo of the National Library of India