Viktor Hess

Viktor Hess

Physicist
Date of Birth: 24.06.1883
Country: Austria

Content:
  1. Biography of Victor Franz Hess
  2. Education and Early Career
  3. Research on Cosmic Rays
  4. Recognition and Later Career
  5. Exile and Later Years

Biography of Victor Franz Hess

Victor Franz Hess was an Austro-American physicist who was born in the Waldstein Castle in the Austrian province of Styria. He was born into the family of Vinzenz Hess, the chief forester of Prince Ottin of Wallerstein's estate, and Seraphina Edle von Grossbauer-Waldstein.

Viktor Hess

Education and Early Career

From 1893 to 1901, Hess attended the gymnasium, after which he enrolled at Graz University. In 1906, he successfully defended his doctoral dissertation in physics with honors. He initially planned to conduct research in optics at the University of Berlin under the guidance of Paul Drude, but had to change his plans following Drude's suicide.

Viktor Hess

While working as a demonstrator and lecturer at the University of Vienna, Hess became interested in the research of Franz Exner and Egon Schweidler on the ionizing effects of radioactive emissions. He discovered that radioactive emissions, such as those from uranium or thorium, caused the surrounding atmosphere to become electrically conductive or ionized. This type of radioactivity could be detected using an electroscope, a device that loses its electric charge due to radiation.

Research on Cosmic Rays

In 1910, Hess joined the Institute for Radium Research at the University of Vienna as a research assistant. It was there that he learned about his colleagues' experiments to determine the source of ionizing radiation in the atmosphere. He also discovered that Theodor Wulf had measured atmospheric ionization in Paris months before. Wulf's measurements, taken from the Eiffel Tower, showed that radiation levels were much higher at its top (at a height of 320 meters) than at its base. These findings contradicted the prevailing theory that radiation could only come from underground sources. Wulf hypothesized that the unusually high radiation level at the top of the tower was caused by radiation coming from the Earth's atmosphere. He approached other scientists with his hypothesis, suggesting that they launch measurement instruments into the atmosphere using balloons.

The following year, Hess developed instruments capable of withstanding significant temperature and pressure changes at high altitudes. He calculated that the maximum height at which terrestrial radiation could ionize the atmosphere was 500 meters. Over the next two years, he launched ten aerosondes with the help of the Austrian Aeronautical Club. "I managed to show," he recalled, "that ionization [in the electroscope] decreased with increasing altitude above the ground (due to the diminishing influence of radioactive substances in the Earth), but starting at an altitude of 1000 meters, it noticeably increased and reached values several times higher than those observed on the Earth's surface at an altitude of 5000 meters." These findings led him to conclude that the ionization could be caused by unknown radiation penetrating the Earth's atmosphere from outer space.

Recognition and Later Career

In 1925, the newly discovered radiation was named "cosmic rays" by American physicist Robert A. Millikan. Hess's experiments drew the attention of other physicists to cosmic rays, including Carl D. Anderson, who discovered the positron, a positively charged particle with the same mass as an electron. Together with Seth H. Neddermeyer, Anderson also discovered the muon, an extremely short-lived particle with a mass about 200 times that of an electron.

In 1919, Hess was appointed assistant professor of physics at the University of Vienna, but in 1920, he moved to Graz where he became an adjunct professor of experimental physics. In 1921, he took a leave of absence and traveled to the United States, where he became the head of the Research Laboratory of the United States Radium Corporation in Orange, New Jersey. He also served as a consultant to the U.S. Bureau of Mines. Hess returned to Graz in 1923, became a full professor two years later, and was appointed dean of the faculty in 1929. In 1931, he became a professor of experimental physics and the director of the Institute for Radiation Research at the University of Innsbruck. He established a research station for cosmic rays under the Hafelekar mountain.

For the discovery of cosmic rays, Hess and Carl D. Anderson were awarded the Nobel Prize in Physics in 1936. The laureates were commended by Hans Pleijel of the Royal Swedish Academy of Sciences for proposing "new important problems related to the formation and destruction of matter, problems that open up new areas for research."

Exile and Later Years

In 1938, two months after Nazi Germany annexed Austria, Hess was removed from his post in Graz because his wife was Jewish, and he himself had served as a scientific advisor to the deposed Chancellor of Austria, Kurt von Schuschnigg. After receiving a warning about an impending arrest, Hess fled to Switzerland. An invitation from Fordham University brought Hess and his wife to New York in 1938. At Fordham, Hess taught physics and eventually obtained U.S. citizenship six years later. In 1946, he was asked to lead the world's first measurements of radioactive fallout in the United States following the atomic bombing of Hiroshima. The following year, Hess and physicist William T. McNeilly developed a method to detect small amounts of radium in the human body by measuring gamma radiation.

In 1920, Hess married Marie Bertha Warner Breisky, who passed away in 1955. In the same year, he married Elizabeth M. Hoenke. After retiring in 1956, Hess continued his research on cosmic rays and radioactivity until the end of his life. He passed away in Mount Vernon, New York, in 1964. Hess received numerous awards and honors throughout his long career, including the Lieben Prize of the Austrian Academy of Sciences (1919), the Ernst Abbe Foundation of Carl Zeiss Award (1932), the honorary medal "For Merit in Art and Science" from the Austrian government (1959), and honorary degrees from the University of Vienna, Loyola University Chicago, Loyola University New Orleans, and Fordham University.

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