Fritz Zwicky

Fritz Zwicky (February 14, 1898February 8, 1974) was an American-based Swiss astronomer. He was an original thinker, with many important contributions in theoretical and observational astronomy.

Biographical sketch

Fritz Zwicky was born in Varna, Bulgaria, to Swiss parents. His father was the Bulgarian ambassador to Norway. He received an advanced education in mathematics and experimental physics at the Swiss Federal Institute of Technology, located in Zürich, Switzerland and in 1925 emigrated to the United States to work with Robert Millikan at California Institute of Technology (Caltech). He was responsible for positing numerous cosmological theories that have a profound impact on understanding of our universe today. He was appointed Professor of Astronomy at Caltech in 1942 and also worked as a research director/consultant for Aerojet Engineering Corporation (1943-1961) and staff member of Mount Wilson Observatory and Palomar Observatory for most of his career. He developed some of the earliest jet engines and is known as the "father of the modern jet engine." Fritz Zwicky holds over 50 patents, many in jet propulsion, and is the inventor of Two Piece Jet Thrust Motor, Inverted Hydro Pulse, Ram Jet and Jet-Assisted Take-Off (JATO).

In April 1932, Fritz Zwicky married Dorothy Vernon Gates, the daughter of a prominent local family and Senator Egbert Gates. Her money was instrumental in the funding of the Palomar Observatory during the Great Depression. Zwicky and Dorothy divorced amicably in 1941, and she admired his intellect until her death in 1988[1]. He remained a life-long friend of his former brother-in-law, Nicholas Roosevelt, cousin of Franklin Delano Roosevelt, and U.S. Minister to Hungary. In 1947 Zwicky was married in Switzerland to Anna Margaritha Zurcher, and they had three daughters, Margrit, Franziska, and Barbarina. His grandchildren are Christian Thomas Pfenninger, Ariella Frances Pfenninger, and Christian Alexander Fritz Zwicky. The Zwicky Museum at the Landesbibliothek, Glarus, houses many of his papers and scientific works, and the Fritz Zwicky Stiftung (Foundation) in Switzerland carries on his ideas relating to "morphological analysis".

Zwicky died in Pasadena on February 8, 1974, just six days before his 76th birthday, and was buried in Mollis, Switzerland, the village where he grew up.

Scientific work

Fritz Zwicky was a prolific scientist and made important contributions in many areas of astronomy.

Supernovae and neutron stars

Together with colleague Walter Baade, Zwicky pioneered and promoted the use of the first Schmidt telescopes used in a mountain-top observatory in 1935. He hand-carried the Schmidt lens from Germany, which had been polished by the optician, Bernard Schmidt. In 1934 he and Baade coined the term "supernova" and hypothesized that they were the transition of normal stars into neutron stars, as well as the origin of cosmic rays[2][3]. It was a prescient insight that had tremendous impact in determining the size and age of the universe in subsequent decades.

In support of this hypothesis, Zwicky started hunting for supernovae, and found a total of 120 by himself (and one more, SN 1963J, in concert with P. Wild) over a stretch of 52 years (SN 1921B through SN 1973K)[4], a record which still stands as of 2006 (the current runner-up is Jean Mueller, with 98 discoveries and 9 co-discoveries).

Standard candles

In 1938, Zwicky's colleague Walter Baade proposed using supernovae as standard candles to estimate distances in deep space[5]. Because light curves of many type Ia supernovae show a common peak luminosity, they establish a cosmological distance scale by a well known intrinsic brightness. Zwicky had been working closely with Baade in supernova investigations at this same time, but their relationship was strained by Zwicky's mandate that Baade not seek credit for Zwicky's work. Baade named a galaxy after himself, that was in fact discovered by Zwicky. Correspondence from Edwin Hubble to Zwicky corrects this nomenclature error and intellectual property theft. Baade feared accountability from Zwicky, and the exposure of his professional misconduct.

Distant Type IA supernovae show a non linear Hubble relationship and scientists have explained this in terms of an acceleration in the expansion rate for the universe[6].

Gravitational lenses

In 1937, Zwicky posited that galaxy clusters could act as gravitational lenses by the previously discovered Einstein effect[7]. It was not until 1979 that this effect was confirmed by observation of the so-called "Twin Quasar" Q0957+561[8].

Dark matter

While examining the Coma galaxy cluster in 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen matter, what is now called dark matter[9]. He was able to infer the average mass of galaxies within the cluster, and obtained a value about 160 times greater than expected from their luminosity, and proposed that most of the matter was dark. The same calculation today shows a smaller factor, based on greater values for the mass of luminous material; but it is still clear that the great majority of matter is dark[10].

His suggestion was not taken very seriously at first, until some forty years later when studies of motions of stars within galaxies also implied the presence of a large halo of unseen matter extending beyond the visible stars. Zwicky's dark matter proposal is now confirmed also by studies of gravitational lensing and cosmological expansion rates. Zwicky portrays the hostility and resistance of the scientific community that he continually encountered as a scientific prophet and visionary. "The Catalogue of Galaxies and Subcompact Galaxies", "The Red Book" addresses the mediocracy of so many in the scientific community, who failed to comprehend his theories, thus hindering the advancement of science for many years by rejecting the very theories they now so readily embrace.

Tired light

When Edwin Hubble discovered a linear relationship between the distance to a galaxy and its redshift expressed as a velocity[11], Zwicky immediately speculated that the effect was due not to motions of the galaxy, but to some inexplicable phenomena that mysteriously caused photons to lose energy as they traveled through space. He considered the most likely candidate process to be a drag effect in which photons transfer momentum to surrounding masses though gravitational interactions; and proposed that an attempt be made to put this effect on a sound theoretical footing with general relativity. He also considered and rejected explanations involving interactions with free electrons, or the expansion of space. [12]

Zwicky was skeptical of the expansion of space in 1929, because the rates measured at that time seemed too large. 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.[13]. Cosmological redshift is now conventionally understood to be a consequence of the expansion of space; a feature of Big Bang cosmology[14].

Morphological analysis

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[15]. He wrote a book on the subject in 1969[16], and claimed that he made many of his discoveries using this method.

Catalog of Galaxies and Clusters

Zwicky devoted considerable time to the search for galaxies and the production of catalogs. From 1961 to 1968 he and his colleagues published a comprehensive six volume Catalogue of galaxies and of clusters of galaxies. They were all published in Pasadena, by the California Institute of Techology.

1. Zwicky, F.; Herzog, E. & Wild, P. (1961), Catalogue of Galaxies and of Clusters of Galaxies (vol 1), <>

2. Zwicky, F. & Herzog, E. (1963), Catalogue of Galaxies and of Clusters of Galaxies (vol 2), <>

3. Zwicky, F. & Herzog, E. (1966), Catalogue of Galaxies and of Clusters of Galaxies (vol 3), <>

4. Zwicky, F. & Herzog, E. (1968), Catalogue of Galaxies and of Clusters of Galaxies (vol 4), <>

5. Zwicky, F.; Karpowicz, M. & Kowal, C.T. (1965), Catalogue of Galaxies and of Clusters of Galaxies (vol 5), <>

6. Zwicky, F. & Kowal, C.T. (1968), Catalogue of Galaxies and of Clusters of Galaxies (vol 6), <>

Galaxies in the original catalog are called Zwicky galaxies, and the catalog is still maintained and updated today[17]. Zwicky with his wife Margaritha also produced an important catalog of compact galaxies, sometimes called simply The Red Book.

Zwicky, F. & Zwicky, M.A. (1971), Catalogue of selected compact galaxies and of post-eruptive galaxies, <>

Guns and goblins

Zwicky was an extraordinarily original thinker, and his contemporaries frequently had no way of knowing which of his ideas would work out and which would not. In a retrospective look at Zwicky's life and work, Stephen Maurer said[18]:

When researchers talk about neutron stars, dark matter, and gravitational lenses, they all start the same way: “Zwicky noticed this problem in the 1930s. Back then, nobody listened . . .”

He is celebrated for the discovery of neutron stars. He also went on to consider nuclear goblins, which he proposed as "a body of nuclear density ... only stable under sufficient external pressure within a massive and dense star". He considered that goblins could move within a star, and explode violently as they reach less dense regions towards the star's surface, and serve to explain eruptive phenomena, such as flare stars[19]. This idea has never caught on.

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. He told his assistant to fire a gun out through the telescope slit, in the hope it would help to smooth out the turbulence. No effect was noticed, but the event shows the kind of lateral thinking for which Zwicky was famous[20]. This valid experiment has been distorted over the years, and despite the best efforts of his night assistant, Ben Traxler, to correct the record shortly before his death, the deliberate embellishments continue.

He was also very proud of his work in producing the first artificial meteors[21]. He placed explosive charges in the nose cone of a V2 rocket, to be detonated at high altitude and fire high velocity pellets of metal through the atmosphere. The first attempts appeared to be failures, and Zwicky sought to try again with the Aerobee rocket. His requests were denied, until the Soviet Union launched Sputnik 1. Twelve days later, on 16 October 1957, Zwicky launched his experiment on the Aerobee, and successfully fired pellets visible from the Mount Palomar observatory. It is thought that one of these pellets may have escaped the gravitational pull of the Earth and become the first object lauched into a solar orbit[18].

Zwicky also considered the possibility of rearranging the universe to our own liking. In a lecture in 1948[22] he spoke of changing planets, or relocating them within the solar system. In the 1960s he even considered how the whole solar system might be moved like a giant spaceship to travel to other stars. 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[23].


It is not widely known that Zwicky was one of the "kindest of men, with a deep concern for humanity" according to Cecilia Payne-Gaposchkin. She further wrote that he was "the last of the scientific individualists, a breed that is dying out in an age of teamwork," in "The Friendly Guide to the Universe", Nancy Hathaway. He was a generous humanitarian with a great concern for wider society. 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 the war ravaged scientific libraries in Europe and Asia—with the aid of departmental funds that he spent without any consultation[24][25].

He also had a longstanding involvement with the charitable Pestalozzi Foundation of America, supporting orphanages. Zwicky received their gold medal in 1955, in recognition of his services[24].

Zwicky loved the mountains, and was an accomplished alpine climber[18].

He was a strong critic of organized religion but not individual faith, and of nationalism, and was critical of political posturing by all sides in the Middle East, and of the use of nuclear weapons in World War 2. He considered that hope for the world lay with free people of good will who work together as needed, without institutions or permanent organizations[26][27].


In 1949, Truman awarded Zwicky the Presidential Medal of Freedom, for work on rocket propulsion during World War II[24]. In 1968, Zwicky was made professor emeritus at California Institute of Technology.

In 1972, Zwicky was awarded the Gold Medal of the Royal Astronomical Society, their most prestigious award, for "distinguished contributions to astronomy and cosmology"[28]. This award noted in particular his work on neutron stars, dark matter, and cataloging of galaxies.

The asteroid 1803 Zwicky, the Zwicky lunar crater, and the galaxy I Zwicky 18 were all named in his honour.


Zwicky produced hundreds of publications over a long career, covering a great breadth of topics. This brief selection, with comments, gives a taste of his work.

* Zwicky, F. (1929), "On the Red Shift of Spectral Lines through Interstellar Space", Proceedings of the National Academy of Science 15: 773–779, <>. This is the article that proposes a tired light model to explain Hubble's law. (full article)

* Baade, W. & Zwicky, F. (1934), "On Super-novae", Proceedings of the National Academy of Science 20 (5): 254–259, <>, and Baade, W. & Zwicky, F. (1934), "Cosmic Rays from Super-novae", Proceedings of the National Academy of Science 20 (5): 259–263, <>. These consecutive articles introduce the notion of a supernova and a neutron star respectively.

* Zwicky, F. (1938), "On Collapsed Neutron Stars", Astrophysical Journal 88: 522–525, <>. The idea of a neutron star, previously introduced in the supernova paper, is explained along with the idea of critical stellar mass and black holes.

* Zwicky, F. (1939), "On the Formation of Clusters of Nebulae and the Cosmological Time Scale", Proceedings of the National Academy of Science 25: 604–609, <>. Zwicky argues that the shape of nebulae indicate a universe far older than can be accounted for by an expanding universe model.

* Zwicky, F. (1941), "A Mosaic Objective Grating for the 18-inch Schmidt Telescope on Palomar Mountain", Publications of the Astronomical Society of the Pacific 53: 242–244, <>. Zwicky was a great advocate for the use of the wide angle Schmidt telescope, which he used to great effect to make many discoveries.

* Zwicky, F. (1945), Report on certain phases of war research in Germany, Aerojet Engineering Corp, <>. Zwicky did work on jet propulsion and other matters with Aerojet corporation during and after the war.

* Zwicky, F. (1957), Morphological astronomy, Springer-Verlag, <>. In this book Zwicky gives free rein to his ideas on morphological research as a tool for making discoveries in astronomy.

* Zwicky, F. (1958), "Nuclear Goblins and Flare Stars", Publications of the Astronomical Society of the Pacific 70: 506–508, <>. As well as proposing neutron stars, Zwicky also proposed unstable aggregations of neutron density matter within larger stars.

* Zwicky, F. (1969), Discovery, invention, research through the morphological approach, MacMillan, <>. Zwicky also proposed that the morphological approach could be applied to all kinds of issues in disciplines going far beyond basic science.

Notes and references

1. ^ Muller, R. (1986), Fritz Zwicky: Leben und Werk des grossen Schweizer Astrophysikers, Raketenforschers und Morphologen (1898-1974), Verlag Baeschlin (also Excerpt of the biography of Fritz Zwicky by Roland Mueller, <>. Retrieved on 14 July 2007)

2. ^ Baade, W. & Zwicky, F. (1934), "On Super-Novae", Proceedings of the National Academy of Sciences 20: 254–259, <>

3. ^ Baade, W. & Zwicky, F. (1934), "Cosmic Rays from Super-novae", Proceedings of the National Academy of Science 20 (5): 259–263, <>

4. ^ List of Supernovae, <>. Retrieved on 10 July 2007 (provided by [CBAT])

5. ^ Baade, W. (1938), "The Absolute Photographic Magnitude of Supernovae", Astrophysical Journal 88: 285–304, <>

6. ^ Perlmutter, S. (2003), "Supernovae, Dark Energy, and the Accelerating Universe", Physics Today 56 (4): 53–60, <>

7. ^ Zwicky, F. (1937), "Nebulae as Gravitational Lenses", Physical Review 51 (4): 290, <>

8. ^ Walsh, D.; Carswell, R.F. & Weymann, R.J. (1979), "0957 + 561 A, B - Twin quasistellar objects or gravitational lens", Nature 279 (5712): 381–384, <>

9. ^ Zwicky, F. (1933). "Die Rotverschiebung von extragalaktischen Nebeln". Helvetica Physica Acta 6: 110–127.​ See also Zwicky, F. (1937). "On the Masses of Nebulae and of Clusters of Nebulae". Astrophysical Journal 86: 217.​

10. ^ Some details of Zwicky's calculation and of more modern values are given in Using the virial theorem: the mass of a cluster of galaxies, <>. Retrieved on 10 July 2007.

11. ^ Hubble, E. (1929). "A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae". Proceedings of the National Academy of Sciences 15 (3): 168–173.​

12. ^ Zwicky, F. (1929). "On the Red Shift of Spectral Lines through Interstellar Space". Proceedings of the National Academy of Sciences 15 (10): 773–779.​ (full article)

13. ^ Baade, W. (1956). "The Period-Luminosity Relation of the Cepheids". Publications of the Astronomical Society of the Pacific 68 (400): 5–16.​

14. ^ Singh, S. (2004). Big Bang. Fourth Estate.

15. ^ Ritchey, T. (2002), General Morphological Analysis: A General Method for Non-Quantified Modelling, <>. Retrieved on 2007-07-10

16. ^ Zwicky, F. (1969), Discovery, Invention, Research Through the Morphological Approach, Toronto: The Macmillian Company, <>

17. ^ The Updated Zwicky Catalog of Galaxies (UZC), <>. Retrieved on 10 July 2007 at the Harvard-Smithsonian Center for Astrophysics.

18. ^ a b c Maurer, S.M. (2001), "Idea Man", Beamline (SLAC) 31 (1), <>. Retrieved on 10 July 2007

19. ^ Zwicky, F. (1958), "Nuclear Goblins and Flare Stars", Publications of the Astronomical Society of the Pacific 70: 506–508, <>

20. ^ Knill, O. (1998), Supernovae, an alpine climb and space travel (biographical notes), <>. Retrieved on 10 July 2007

21. ^ Zwicky, F. (1946), "On the Possibility of Earth-Launched Meteors", Publications of the Astronomical Society of the Pacific 58: 260–261, <>

22. ^ Zwicky, F. (1948), "Morphological astronomy", The Observatory 68: 121–143, <>

23. ^ Zwicky, F. (1966), Entdecken, Erfinden, Forschen im morphologischen Weltbild, Muenchen: Droemer, <> (page 237). This reference was identified from a footnote provided in an online essay: Knill, Oliver (1997), Moving the Solar System, <>. Retrieved on 17 July 2007.

24. ^ a b c Greenstein, J.L. (1974), "Fritz Zwicky - Scientific Eagle (obituary)", Engineering and Science (CalTech): 15–19, <>. Retrieved on 14 July 2007

25. ^ Fritz Zwicky's Extraordinary Vision, <>. Retrieved on 16 July 2007, an extract from Soter, S. (2000), Cosmic Horizons: Astronomy at the Cutting Edge, New Press, <>

26. ^ Zwicky, F. (1949), "Free World Agents of Democracy", Engineering and Science (California Institute of Technology) 13 (2), <>

27. ^ Wilson, A. (1975), "Fritz Zwicky (obituary)", Quarterly Journal of the Royal Astronomical Society 16: 106–108, <>

28. ^ Meeting of the Royal Astronomical Society, 1972, <>. Retrieved on 14 July 2007


* Richey, T., Fritz Zwicky, <>. Retrieved on 10 July 2007

* Maurer, S.M. (2001), "Idea Man", Beamline (SLAC) 31 (1), <>. Retrieved on 10 July 2007

* Knill, O. (1998), Supernovae, an alpine climb and space travel (biographical notes), <>. Retrieved on 10 July 2007


Retrieved from ""
All text is available under the terms of the GNU Free Documentation License


Scientific Library -