Fritz Zwicky

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Fritz Zwicky
BornFebruary 14, 1898
DiedFebruary 8, 1974(1974-02-08) (aged 75)
Alma mater Swiss Federal Polytechnic
Known for Dark matter, supernovae, galaxies as gravitational lenses, neutron stars
AwardsPresident's Medal of Freedom (1949)
Gold Medal of the Royal Astronomical Society (1972)
Scientific career
Fields Astronomy
Institutions California Institute of Technology
Doctoral advisor Peter Debye and Paul Scherrer

Fritz Zwicky ( /ˈtsvɪki/ ; [1] German: [ˈtsvɪki] ; February 14, 1898 – February 8, 1974) was a Swiss astronomer. 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 infer the existence of unseen dark matter, describing it as "dunkle (kalt) Materie". [3] [4]



Fritz Zwicky was born in Varna, Bulgaria, to a Swiss father. His father, Fridolin (b. 1868), was a prominent industrialist in the Bulgarian city and also served as ambassador of Norway in Varna (1908–1933). [5] The Zwicky House in Varna was designed and built by Fridolin Zwicky. Fritz's mother, Franziska Vrček (b. 1871), was an ethnic Czech of the Austro-Hungarian Empire. Fritz was the oldest of the Zwicky family's three children: he had a younger brother named Rudolf and a sister, Leonie. Fritz's mother died in Varna in 1927, and his father Fridolin remained in Bulgaria until 1945, when he returned to Switzerland. His sister Leonie married a Bulgarian from Varna and spent her entire life in the city. [6]

In 1904, at the age of six, Fritz was sent to his grandparents in the family's ancestral canton of Glarus, Switzerland, to study commerce. [7] His interests shifted to math and physics and he received an advanced education in mathematics and experimental physics at the Swiss Federal Polytechnic (today known as ETH Zurich) in Zurich. In 1925, he immigrated to the United States to work with Robert Millikan at California Institute of Technology (Caltech) with an office down the hall from Robert Oppenheimer after receiving the "international fellowship from the Rockefeller Foundation." [7]

He was responsible for positing numerous cosmological theories that have a profound impact on the understanding of our universe today. He coined the term "supernova" during his fostering the concept of neutron stars. It would be five years later when Oppenheimer would publish his landmark paper announcing "neutron stars". Fritz 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 holds over 50 patents, many in jet propulsion, and is the inventor of the Underwater Jet (TIME March 14, 1949), the Two Piece Jet Thrust Motor and Inverted Hydro Pulse. [8]

In April 1932, Fritz Zwicky married Dorothy Vernon Gates (1904-1991), a member of a prominent local family and a daughter of California State Senator Egbert Gates. Her money was instrumental in the funding of the Palomar Observatory during the Great Depression. Nicholas Roosevelt, cousin of President Theodore Roosevelt, was his brother-in-law by marriage to Tirzah Gates. Zwicky and Dorothy divorced amicably in 1941. [9] In 1947 Zwicky was married in Switzerland to Anna Margaritha Zurcher and they had three daughters, Margrit, Franziska, and Barbarina. 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, and was buried in Mollis, Switzerland.

Zwicky was an atheist. [10]

He is remembered as both a genius and a curmudgeon. [11] One of his favorite insults was to refer to people he did not approve of as "spherical bastards", because, he explained, they were bastards no matter which way one looked at them. [12]

A recent biography in English was published by the Fritz Zwicky Foundation: Alfred Stöckli & Roland Müller: Fritz Zwicky – An Extraordinary Astrophysicist. Cambridge Scientific Publishers, Cambridge, 2011. A review of the book is available from Acta Morphologica Generalis.

Scientific work

The memorial plaque on the house in Varna where Zwicky was born. His contributions to the understanding of the neutron stars and the dark matter are explicitly mentioned. Fritz Zwicky Memorial Plate - Varna.jpg
The memorial plaque on the house in Varna where Zwicky was born. His contributions to the understanding of the neutron stars and the dark matter are explicitly mentioned.

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

Ionic crystals and electrolytes

His first scientific contributions pertained to ionic crystals and electrolytes.

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. In 1934 he and Baade coined the term "supernova" and hypothesized that supernovae were the transition of normal stars into neutron stars, [13] as well as the origin of cosmic rays. [14] [15] This was an opinion which contributed to determining the size and age of the universe subsequently.

In support of this hypothesis, Zwicky started looking for supernovae, and found a total of 120 by himself (and one more, SN 1963J, in concert with Paul Wild) over 52 years (SN 1921B through SN 1973K), [16] a record which stood until 2009 when passed by Tom Boles. 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.

Gravitational lenses

In 1937, Zwicky posited that galaxies could act as gravitational lenses by the previously discovered Einstein effect. [17] It was not until 1979 that this effect was confirmed by observation of the so-called "Twin Quasar" Q0957+561. [18]

Dark matter

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 (kalt) Materie 'dark matter'. [3] The gravitational anomaly surfaced due to the excessive rotational velocity of luminous matter compared to the calculated gravitational attraction within the cluster. 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. 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 was correctly inferred to be dark. [19]

Tired light

When Edwin Hubble discovered a somewhat linear relationship between the distance to a galaxy and its redshift expressed as a velocity, [20] Zwicky immediately pointed out that the correlation between the calculated distances of galaxies and their redshifts had a discrepancy too large to fit in the distance's error margins. 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. He considered the most likely candidate process to be a drag effect in which photons transfer momentum to surrounding masses through 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. [21]

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. [22] Cosmological redshift is now conventionally understood to be a consequence of the expansion of space; a feature of Big Bang cosmology. [23]

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. [24] He wrote a book on the subject in 1969, [25] 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 Technology.

  1. Zwicky, F.; Herzog, E.; Wild, P. (1961), Catalogue of Galaxies and of Clusters of Galaxies, 1, California Institute of Technology,
  2. Zwicky, F.; Herzog, E.; Wild, P. (1963), Catalogue of Galaxies and of Clusters of Galaxies, 2, California Institute of Technology,
  3. Zwicky, F.; Herzog, E.; Wild, P. (1966), Catalogue of Galaxies and of Clusters of Galaxies, 3, California Institute of Technology,
  4. Zwicky, F.; Herzog, E., Catalogue of Galaxies and of Clusters of Galaxies, 4, California Institute of Technology
  5. Zwicky, F.; Karpowicz, M.; Kowal, C.T. (1965), Catalogue of Galaxies and of Clusters of Galaxies, 5, California Institute of Technology,
  6. Zwicky, F.; Kowal, C.T. (1968), Catalogue of Galaxies and of Clusters of Galaxies, 6, California Institute of Technology, Bibcode:1968cgcg.bookR....Z

Galaxies in the original catalog are called Zwicky galaxies, and the catalog is still maintained and updated today. [26] 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", Guemligen: Zwicky,

Original thinker

Zwicky was an 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: [27]

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. [28] 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. [29]

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". [30] Zwicky later admitted that he had been mistaken.

He was also very proud of his work in producing the first artificial meteors. [31] 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 October 16, 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 launched into a solar orbit. [27]

Zwicky also considered the possibility of rearranging the universe to our own liking. In a lecture in 1948 [32] 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. [33]


Zwicky 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 war-ravaged scientific libraries in Europe and Asia. [34] [35]

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. [34]

Zwicky loved the mountains, and was an accomplished alpine climber. [27]

He was critical of political posturing by all sides in the Middle East, and of the use of nuclear weapons in World War II. He considered that hope for the world lay with free people of good will who work together as needed, without institutions or permanent organizations. [36] [37]



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.

Related Research Articles

Dark matter Hypothetical form of matter comprising most of the matter in the universe

Dark matter is a form of matter thought to account for approximately 85% of the matter in the universe and about a quarter of its total energy density. Its presence is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained by accepted theories of gravity unless more matter is present than can be seen. For this reason, most experts think that dark matter is abundant in the universe and that it has had a strong influence on its structure and evolution. Dark matter is called dark because it does not appear to interact with observable electromagnetic radiation, such as light, and so it is undetectable by existing astronomical instruments.

Galaxy Gravitationally bound astronomical structure

A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek galaxias (γαλαξίας), literally "milky", a reference to the Milky Way. Galaxies range in size from dwarfs with just a few hundred million stars to giants with one hundred trillion stars, each orbiting its galaxy's center of mass.

Gravitational lens Matter distribution between distant light source and observer

A gravitational lens is a distribution of matter between a distant light source and an observer, that is capable of bending the light from the source as the light travels towards the observer. This effect is known as gravitational lensing, and the amount of bending is one of the predictions of Albert Einstein's general theory of relativity.

Astronomy Scientific study of celestial objects and phenomena

Astronomy is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates outside Earth's atmosphere. Cosmology is a branch of astronomy. It studies the Universe as a whole.

Andromeda Galaxy spiral galaxy within the Local Group

The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula, is a spiral galaxy approximately 2.5 million light-years from Earth, and the nearest major galaxy to the Milky Way. The galaxy's name stems from the area of the Earth's sky in which it appears, the constellation of Andromeda.

Astronomical object Large natural physical entity in space

An astronomical object or celestial object is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms object and body are often used interchangeably. However, an astronomical body or celestial body is a single, tightly bound, contiguous entity, while an astronomical or celestial object is a complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures.

In astronomy, the term compact star refers collectively to white dwarfs, neutron stars, and black holes. It would grow to include exotic stars if such hypothetical, dense bodies are confirmed to exist. All compact objects have a high mass relative to their radius, giving them a very high density, compared to ordinary atomic matter.

Messier 87 Galaxy in the Virgo Galactic Cluster

Messier 87 is a supergiant elliptical galaxy in the constellation Virgo. One of the most massive galaxies in the local universe, it has a large population of globular clusters—about 12,000 compared with the 150–200 orbiting the Milky Way—and a jet of energetic plasma that originates at the core and extends at least 1,500 parsecs, traveling at a relativistic speed. It is one of the brightest radio sources in the sky and a popular target for both amateur and professional astronomers.

Stellar population Grouping of stars by similar metallicity

During 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. By the way, in the abstract of the article by Bade, he recognizes that Jan Oort originally conceived this type of classification in 1926: "[...] The two types of stellar populations had been recognized among the stars of our own galaxy by Oort as early as 1926". Baade noticed that bluer stars were strongly associated with the spiral arms and yellow stars dominated near the central galactic bulge and within globular star clusters. Two main divisions were defined as Population I and Population II, with another newer division called Population III added in 1978, which are often simply abbreviated as Pop I, II or III.

Astronomical spectroscopy science of temporal, spatial, and spectral distributions of radiation

Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light and radio, which radiates from stars and other celestial objects. A stellar spectrum can reveal many properties of stars, such as their chemical composition, temperature, density, mass, distance, luminosity, and relative motion using Doppler shift measurements. Spectroscopy is also used to study the physical properties of many other types of celestial objects such as planets, nebulae, galaxies, and active galactic nuclei.

Walter Baade German astronomer

Wilhelm Heinrich Walter Baade was a German astronomer who worked in the United States from 1931 to 1959.

Messier 84 galaxy

Messier 84 or M84, also known as NGC 4374, is an elliptical or lenticular galaxy in the constellation Virgo. Charles Messier discovered Messier 84 on 18 March 1781 in a systematic search for "nebulous objects" in the night sky. The object is the 84th in the Messier Catalogue. M84 is situated in the heavily populated inner core of the Virgo Cluster of galaxies.

Coma Cluster cluster of galaxies in the constellation Coma Berenices

The Coma Cluster is a large cluster of galaxies that contains over 1,000 identified galaxies. Along with the Leo Cluster, it is one of the two major clusters comprising the Coma Supercluster. It is located in and takes its name from the constellation Coma Berenices.

History of supernova observation

The known history of supernova observation goes back to 185 AD, when supernova SN 185 appeared, the oldest appearance of a supernova recorded by humankind. Several additional supernovae within the Milky Way galaxy have been recorded since that time, with SN 1604 being the most recent supernova to be observed in this galaxy.

Tidal tail thin, elongated region of stars and interstellar gas that extends into space from a galaxy

A tidal tail is a thin, elongated region of stars and interstellar gas that extends into space from a galaxy. Tidal tails occur as a result of galactic tide forces between interacting galaxies. Examples of galaxies with tidal tails include the Tadpole Galaxy and the Mice Galaxies. Tidal forces can eject a significant amount of a galaxy's gas into the tail; within the Antennae Galaxies, for example, nearly half of the observed gaseous matter is found within the tail structures. Within those galaxies which have tidal tails, approximately 10% of the galaxy's stellar formation takes place in the tail. Overall, roughly 1% of all stellar formation in the known universe occurs within tidal tails.

In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space.

Nicholas Mayall American astronomer

Nicholas Ulrich Mayall was an American observational astronomer. After obtaining his doctorate from the University of California, Berkeley, Mayall worked at the Lick Observatory, where he remained from 1934 to 1960, except for a brief period at MIT's Radiation Laboratory during World War II.

MACS J1149 Lensed Star 1 blue supergiant, the most distant star detected at 9 billion light years from Earth

MACS J1149 Lensed Star 1, also known as Icarus, is a blue supergiant star observed through a gravitational lens. It is the most distant individual star detected, at approximately 14 billion light-years from Earth, as of April 2018. Light from the star was emitted 4.4 billion years after the Big Bang. According to co-discoverer Patrick Kelly, the star is at least a hundred times more distant than the next-farthest non-supernova star observed, SDSS J1229+1122, and is the first magnified individual star seen.


  1. "Zwicky". Random House Webster's Unabridged Dictionary .
  2. Arp, Halton (June 1974). "Fritz Zwicky". Physics Today. 27 (6): 70–71. Bibcode:1974PhT....27f..70A. doi:10.1063/1.3128662. Archived from the original on 2013-09-27.
  3. 1 2 Zwicky, F. (1933), "Die Rotverschiebung von extragalaktischen Nebeln", Helvetica Physica Acta, 6: 110–127, Bibcode:1933AcHPh...6..110Z See also Zwicky, F. (1937), "On the Masses of Nebulae and of Clusters of Nebulae", Astrophysical Journal, 86: 217, Bibcode:1937ApJ....86..217Z, doi:10.1086/143864
  4. de Swart, J. G.; Bertone, G.; van Dongen, J. (2017). "How dark matter came to matter". Nature Astronomy. 1 (59): 0059. arXiv: 1703.00013 . Bibcode:2017NatAs...1E..59D. doi:10.1038/s41550-017-0059.
  5. "Организират конференция, посветена на родения във Варна астроном Фриц Цвики" (in Bulgarian). Днес+. 2008-02-13. Archived from the original on 1 February 2010. Retrieved 18 March 2010.
  6. Ivanova, Natasha (2008), "110th anniversary of the astrophysicist Fritz Zwicky", Bulgarian Astronomical Journal (in Bulgarian), 10: 135, Bibcode:2008BlgAJ..10..135I
  7. 1 2 Richard Panek, The Father of Dark Matter. Discover. 2009. pp. 81-87.
  8. U.S. Patent # 3044252
  9. Muller, R. (1986), Fritz Zwicky: Leben und Werk des grossen Schweizer Astrophysikers, Raketenforschers und Morphologen (1898-1974) (in German), Verlag Baeschlin
  10. Swiss-American Historical Society (2006). Newsletter, Volumes 42-43. The Society. p. 17. Zwicky has dealt critically with religion during his whole life. A 1971 diary entry states: "To base the inexplainabilty and the immense wonder of nature upon another miracle, God, is unnecessary and not acceptable for any serious thinker." According to one story, Zwicky once discussed the beginning of the universe with a priest. The priest, quoting Scriptures, stated that the universe had started with "and there is light." Zwicky replied that he would buy this, if instead God had said "and there is electromagnetism".
  11. "The Father of Dark Matter Still Gets No Respect -".
  12. Ken Freeman, Geoff Mcnamara, In Search of Dark Matter p22-23 ISBN   978-0-387-27616-8
  13. Osterbrock, D. E. (2001). "Who Really Coined the Word Supernova? Who First Predicted Neutron Stars?". Bulletin of the American Astronomical Society . 33: 1330. Bibcode:2001AAS...199.1501O.
  14. Baade, W.; Zwicky, F. (1934), "On Super-Novae", Proceedings of the National Academy of Sciences, 20 (5): 254–259, Bibcode:1934PNAS...20..254B, doi:10.1073/pnas.20.5.254, PMC   1076395 , PMID   16587881
  15. Baade, W.; Zwicky, F. (1934), "Cosmic Rays from Super-novae", Proceedings of the National Academy of Sciences, 20 (5): 259–263, Bibcode:1934PNAS...20..259B, doi:10.1073/pnas.20.5.259, PMC   1076396 , PMID   16587882
  16. List of Supernovae , retrieved 2007-07-10 (provided by CBAT)
  17. Zwicky, F. (February 1937), "Nebulae as Gravitational Lenses", Physical Review , 51 (4): 290, Bibcode:1937PhRv...51..290Z, doi:10.1103/PhysRev.51.290
  18. Walsh, D.; Carswell, R.F.; Weymann, R.J. (May 31, 1979), "0957 + 561 A, B - Twin quasistellar objects or gravitational lens", Nature, 279 (5712): 381–384, Bibcode:1979Natur.279..381W, doi:10.1038/279381a0, PMID   16068158
  19. Some details of Zwicky's calculation and of more modern values are given in Richmond, M., Using the virial theorem: the mass of a cluster of galaxies , retrieved 2007-07-10.
  20. 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, Bibcode:1929PNAS...15..168H, doi:10.1073/pnas.15.3.168, PMC   522427 , PMID   16577160
  21. Zwicky, F. (1929), "On the Red Shift of Spectral Lines through Interstellar Space", Proceedings of the National Academy of Sciences, 15 (10): 773–779, Bibcode:1929PNAS...15..773Z, doi:10.1073/pnas.15.10.773, PMC   522555 , PMID   16577237 (full article)
  22. Baade, W. (1956), "The Period-Luminosity Relation of the Cepheids", Publications of the Astronomical Society of the Pacific, 68 (400): 5–16, Bibcode:1956PASP...68....5B, doi:10.1086/126870
  23. Singh, S. (2004), Big Bang, Fourth Estate, archived from the original on 2007-06-30
  24. Ritchey, T. (2002), General Morphological Analysis: A General Method for Non-Quantified Modelling (PDF), retrieved 2007-07-10
  25. Zwicky, F. (1969), Discovery, Invention, Research Through the Morphological Approach, Toronto: The Macmillan Company
  26. The Updated Zwicky Catalog of Galaxies (UZC) , retrieved 2007-07-10 at the Harvard-Smithsonian Center for Astrophysics.
  27. 1 2 3 Maurer, S.M. (2001), "Idea Man" (PDF), Beamline, 31 (1), retrieved 2007-07-10
  28. Zwicky, F. (October 1958), "Nuclear Goblins and Flare Stars", Publications of the Astronomical Society of the Pacific (journal), 70 (416): 506–508, Bibcode:1958PASP...70..506Z, doi:10.1086/127284
  29. Knill, O. (1998), Supernovae, an alpine climb and space travel (biographical notes) , retrieved 2007-07-10
  31. Zwicky, F. (August 1946), "On the Possibility of Earth-Launched Meteors", Publications of the Astronomical Society of the Pacific (journal), 58 (343): 260–261, Bibcode:1946PASP...58..260Z, doi:10.1086/125840
  32. Zwicky, F. (August 1948), "Morphological astronomy", The Observatory (journal), 68: 121–143, Bibcode:1948Obs....68..121Z
  33. Zwicky, F. (1966), "Entdecken, Erfinden, Forschen im morphologischen Weltbild", Muenchen: Droemer (book), Muenchen, (page 237). This reference was identified from a footnote provided in an online essay: Knill, Oliver (November 1997), Moving the Solar System , retrieved 2007-07-17.
  34. 1 2 3 Greenstein, J.L. (March–April 1974), "Fritz Zwicky – Scientific Eagle (obituary)" (PDF), Engineering and Science: 15–19, retrieved 2007-07-14
  35. Fritz Zwicky's Extraordinary Vision, American Museum of Natural History, archived from the original on 2007-07-14, retrieved 2007-07-16, an extract from Soter, S.; Tyson, N.D. (2000), Cosmic Horizons: Astronomy at the Cutting Edge , New Press, ISBN   978-1565846029
  36. Zwicky, F. (November 1949), "Free World Agents of Democracy" (PDF), Engineering and Science, 13 (2)
  37. Wilson, A. (1975), "Fritz Zwicky (obituary)", Quarterly Journal of the Royal Astronomical Society, 16: 106–108, Bibcode:1975QJRAS..16..106.
  38. "Dr. Fritz Zwicky, Astronomer, Jet Propulsion Expert, 74, Dies". The New York Times. February 11, 1974.
  39. Meeting of the Royal Astronomical Society (PDF), February 1972, retrieved 2007-07-14
  40. "Zwicky Transient Facility Opens Its Eyes to the Volatile cosmos". Zwicky Transient Facility. November 14, 2017.


Further reading