Fritz Zwicky

Astronomer

• Born: February 14, 1898
• Birthplace: Varna, Bulgaria
• Died: February 8, 1974
• Place of death: Pasadena, California

Swiss American astronomer

Astronomer and physicist Fritz Zwicky observed and named the supernova phenomenon. He also theorized the existence of neutron stars and dark matter, and patented numerous inventions related to jet propulsion.

Born: February 14, 1898; Varna, Bulgaria

Died: February 8, 1974; Pasadena, California

Primary fields: Astronomy; physics

Specialties: Astrophysics; theoretical astronomy; observational astronomy; condensed-matter (solid state) physics

Early Life

Fritz Zwicky was born on February 14, 1898, in Varna, Bulgaria. He was the eldest of the three children of wealthy Swiss merchant and longtime Bulgarian resident Fridolin Zwicky and his Czech wife, Franziska Wrcek Zwicky. When he was six years old, Zwicky was sent to Glarus, Switzerland, where his father’s family had originated. He lived with his grandparents and enrolled at a boarding school in the village of Mollis. During his early education, when he demonstrated skills in scientific subjects, Zwicky became an avid skier and mountain climber; he would retain a strong interest in sports throughout his life.

At the age of sixteen, Zwicky moved to Zurich. In 1916, he entered the Swiss Federal Institute of Technology, initially intending to follow his father into the world of business. However, he decided to pursue science and, with his father’s permission, switched his focus to physics and mathematics. After taking courses from such teachers as physicist Albert Einstein, mathematician Herman Weyl, physicist Auguste Piccard, chemist Peter Debye, and physicist Paul Scherrer, Zwicky graduated with a bachelor’s degree in 1920. He subsequently earned his PhD in physics in 1922 and remained at the institute for the next three years as a teacher of the subject.

In 1925, Robert A. Millikan, winner of the 1923 Nobel Prize in Physics, invited Zwicky to become a physics professor at the California Institute of Technology (Caltech). Zwicky accepted and relocated to Pasadena, where, for two years after assuming his teaching duties, he conducted research on the quantum theory of solids and liquids under a Rockefeller Fellowship provided by the International Education Board.

Life’s Work

During Zwicky’s years as an assistant professor of physics at Caltech, (1925–29) and associate professor (1929–42), he became known as a brilliant but quirky scientist. Recognized for his studies and publications on crystals, solid-state physics, ionization, and thermodynamics, Zwicky also earned a reputation for his peculiar sense of humor and his arrogance. In 1932, he married Dorothy Vernon Gates, the daughter of a wealthy California businessman; they divorced in 1941.

In the early 1930s, Zwicky’s interests drifted toward astrophysics, with a focus on cosmic rays. He began working with German astronomer Walter Baade at the Mount Wilson and Palomar Observatories in southern California. During that decade, the two scientists concentrated their attention on distant galaxies, particularly infrequent extra-large stellar nuclear explosions, for which they coined the term “supernovae,” because the event is considerably more energetic—more than one hundred million times brighter than the sun—than an ordinary nova. Zwicky theorized that supernovae create great bursts of cosmic rays in the process of becoming small-scale, extremely dense neutron stars. His hypotheses would not be proven for more than thirty years.

In the mid-1930s, Zwicky and Baade convinced Caltech to fund the installation of a wide-angle, low-distortion eighteen-inch Schmidt telescope at Mount Palomar, the first such instrument in North America. With the new telescope, Zwicky and numerous collaborators began scanning the skies for supernovae. Their search yielded most of the known supernovae—Zwicky himself discovered more than 120—and resulted in the 1960s in a six-volume catalog of some thirty thousand galaxies and galaxy clusters where the majority of supernovae occur. The Catalogue of Galaxies and of Clusters of Galaxies (1961–68) became a standard reference for the study of galaxies.

It was also during the 1930s that Zwicky suggested the existence of dark matter. In 1933, while studying the Coma Cluster of galaxies, he found that the galaxies have dispersed velocities. This indicated that a large, invisible mass has to be holding the cluster together. He called the unknown mass “dunkle materie,” or dark matter. After estimating the mass of the Coma Cluster, first by measurements of galactic luminosities and then by measurements based on galactic velocities, he found the cluster’s velocity-based mass to be four hundred times larger than his estimate based on luminosity. This, he postulated, means that the Coma Cluster is mostly composed of dark matter; by extension, most of the universe must be composed of dark matter.

In 1942, Zwicky became Caltech’s first full professor of astrophysics, a position he retained until his retirement more than twenty-five years later. He specialized in teaching graduate-level courses in analytical mechanics and advanced seminars in astronomy.

That same year, Zwicky became a founder—along with Clark B. Millikan, Caltech aeronautics professor and son of Robert A. Millikan, and Hungarian-born aerospace engineer-physicist Theodore von Kármán—of Aerojet Engineering Corporation in Azusa, California. The company, formed during World War II, was initially established to create rocket engines to assist the launch of heavily laden bombers. Zwicky served as director of research at Aerojet (later a subsidiary of GenCorp) from 1943 to 1946, and was associated with the company as a technical adviser until the late 1950s.

After the end of the war, Zwicky traveled to Germany and Japan to visit secret weapons facilities, where he gained ideas that helped Aerojet develop high-energy fuels later used in solid-fuel rocket boosters. During his tenure at Aerojet, Zwicky patented dozens of concepts and pieces of high-tech equipment related to jet propulsion. In 1946, he used reconstituted German V-2 rocket to launch an artificial meteor to study the behavior of genuine meteors. In 1957, Zwicky experimented with the Aerobee rocket, a type of sounding rocket created by Aerojet to test and push the limits of traveling through Earth’s atmosphere. The rocket reached an altitude of fifty-four miles above the southwestern United States, when high explosives blew it up. The blast launched streams of metal into space, and it is believed that one stream escaped from Earth’s gravity to become the first man-made object to achieve orbit around the sun.

In 1947, Zwicky, by then a dual American-Swiss citizen, married Swiss native Anna Margaritha Zuercher. The couple would have three daughters: Margarit, Franziska, and Barbarina. A member of the American Astronautical Society, Zwicky also served as vice president of the International Academy of Astronautics. In 1949, US president Harry S. Truman awarded Zwicky the Medal of Freedom. He received the Royal Astronomical Society Gold Medal in 1972.

Throughout the 1950s and 1960s, Zwicky continued to teach, conduct astronomical research, and publish extensively; he wrote more than three hundred papers and books during his lifetime. Zwicky formally retired from Caltech, becoming professor emeritus, in 1968. He died of a heart attack on February 8, 1974.

Impact

Zwicky was one of the most influential astronomer-astrophysicists in the United States during the twentieth century. Though the scientific community dismissed many of Zwicky’s theories at the time of their publication—concerning supernovae, star clusters, galaxy masses and distances, neutron stars, cosmic rays, and blue, quasar-like stars—his theories were later shown to be accurate once technology had advanced sufficiently to confirm them. Zwicky’s hypothesis that most of the universe is composed of dark matter has become widely accepted as true, and studies of dark matter continue in an attempt to unravel and understand those mysterious forces. In addition, the confirmed existence of neutron stars and supernovae has helped scientists understand the formation of galaxies in the universe.

Despite his sometimes arrogant personality, Zwicky had a large humanitarian streak. After World War II, he restocked many European scientific libraries destroyed in the conflagration and was a driving force in helping set up institutions for war orphans. Recognized both during and after his lifetime for his scientific and charitable achievements, Zwicky was inducted posthumously into the International Space Hall of Fame in 1976. An asteroid, a lunar crater, and a galaxy have been named in his honor. The Fritz Zwicky Foundation and Zwicky Museum, which houses his scientific papers and preserves his legacy, was established in Glarus, Switzerland, where he is buried.

Bibliography

Bartusiak, Marcia, ed. Archives of the Universe: 100 Discoveries that Transformed Our Understanding of the Cosmos. New York: Vintage, 2006. Print. A collection of essays and excerpts from scientific papers—including samples of Zwicky’s groundbreaking writings—encompassing the study of the cosmos.

Gates, Evalyn. Einstein’s Telescope: The Hunt for Dark Matter and Dark Energy in the Universe. New York: Norton, 2010. Print. An illustrated discussion of Einstein’s theory of gravitational lensing, which Zwicky used in his theory about dark matter.

Impey, Chris. How It Began: A Time-Traveler’s Guide to the Universe. New York: Norton, 2012. Print. An overview of significant milestones achieved in the scientific examination of the universe, including Zwicky’s observations of distant galaxies.