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  • Fritz Zwicky

    Reggie Jones
    This week in February marks the 126th birthday for Swiss astronomer Fritz Zwicky [1898-1974].
    Born in Bulgaria to Swiss-Czech parents, he was sent to live with his grandparents in Switzerland in 1904. In Switzerland, he earned his education in mathematics & physics at the polytechnic school in Zurich, which is now the Swiss Federal Institute of Technology in Zurich (ETH Zurich; Eidgenössische Technische Hochschule Zürich).
    He came to the United States in 1925, on an international fellowship from the Rockefeller Foundation, to work at Caltech with Robert Millikan [1868-1953], who had received the 1923 Nobel Prize in physics. Zwicky became an active & productive astronomer at both Mt. Wilson and Palomar Observatories, as well as holding a professorship in astronomy at Caltech. His name is well known throughout the astronomical community, both amateur & professional.
    Zwicky and Walter Baade [1893-1960] correctly identified supernovae as the event signaling the birth of a neutron star, and Zwicky was first to suggest using supernovae as standard candles for distance determination, which is now known to work for Type-Ia supernovae (Zwicky was also the one who coined the word "supernova").
    Zwicky predicted that galaxy clusters could act as gravitational lenses, a phenomenon that is now also a standard tool in cosmology, used to find otherwise invisible, but gravitationally lensed & magnified galaxies far behind a foreground cluster.
    Zwicky was also the first to use the virial theorem and galaxy cluster dynamics to infer the presence of unseen matter via its gravity. This remains, in more detailed form, the basis for the modern hypothesis for dark matter, and in fact, Zwicky was the first to use the term “dark matter” (German: dunkle Materie).  He is also very well known for his still relevant Zwicky Catalog of galaxies & galaxy clusters.
    But not all of Zwicky’s ideas survived the test of time. He, and a number of others, were skeptical about an expanding universe, for a number of technical reasons. Zwicky championed the idea of “tired light”, an unknown process causing photons to lose energy as they propagate over cosmological distances. If he ever came around to accepting the expanding universe of the Big bang, it was only after the mid 1950s, when Baade corrected the last of the major problems with the Big bang distance scales.
    Zwicky was also a generous philanthropist, and during WWII made a significant effort to collect books for war-ravaged libraries in Europe, and in 1955 received a Gold Medal from the Pestalozzi Foundation of America for supporting their orphanages.
    But that generosity did not prevent Zwicky from being something of a curmudgeon in the workplace, where he was famously not an easy collaborator. He even coined the term “spherical bastard” to describe people he didn’t like, of which there were many, because, as he put it, they were still bastards, no matter from which direction you looked at them.
    The undated picture here shows Zwicky at the controls of the 18-inch Schmidt telescope (really a Schmidt camera), that came to Palomar Observatory in 1935. The telescope/camera was the brainchild of German-Estonian optician Bernhard Schmidt [1879-1935], who first began to build them in 1930. The intention is to provide a wide field of view, but with limited aberrations. Zwicky was an early advocate of Schmidt cameras, and so he is one of the reasons why they flourished as soon as they did.
    http://scihi.org/fritz-zwicky-dark-matter/ (“Fritz Zwicky and the Existence of Dark Matter”)
    https://www.swemorph.com/zwicky.html (Swedish Morphological Society)
    https://www.nmspacemuseum.org/inductee/fritz-zwicky/ (International Space Hall of Fame - New Mexico Museum of Space History)
    https://mathshistory.st-andrews.ac.uk/Biographies/Zwicky/ (Mathematical biography - University of St. Andrews, Scotland)
    https://physicsworld.com/.../the-tempestuous-genius-of.../ (“The tempestuous genius of Fritz Zwicky” - Physics World, 21 December 2019)
    https://www.sciencefocus.com/.../fritz-zwicky-part.../ (“Fritz Zwicky: Part eccentric, part genius, completely uncontained” - BBC Science Focus, 22 November 2019)
    https://www.amnh.org/.../cosmic-horizons-book/franz-zwicky (“Profile: Fritz Zwicky's Extraordinary Vision” - American Museum of Natural History)
    https://ecuip.lib.uchicago.edu/mul.../optical/impact/09.html (Zwicky Supernova Survey - University of Chicago)
    https://oac.cdlib.org/findaid/ark:/13030/c8kh0tg5/ (Fritz Zwicky papers, Online Archive of California)
    https://www.zwicky-stiftung.ch/ (Fritz Zwicky Foundation, “holds and manages Fritz Zwicky’s entire estate”)
    http://tdc-www.harvard.edu/uzc/ (Updated Zwicky catalog of Galaxies at the Smithsonian Astrophysical Observatory)
    https://ned.ipac.caltech.edu/.../Sept02/Zwicky/frames.html (Original Zwicky catalog of galaxies; Zwicky, 1971)
    https://zwickymeeting.astro.phys.ethz.ch/zwicky.php (Inaugural Zwicky Symposium, 2015; Photo source)
    https://en.wikipedia.org/wiki/Schmidt_camera (Schmidt camera - Wikipedia)
    Originally posted by Tim Thompson, Senior Astronomer JPL (Retired)


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