Johannes Wilhelm "Hans" Geiger (pronounced GYE-ger or GYE-guh; German: [ˈɡaɪɡɐ]; September 30, 1882 – September 24, 1945) was a German scientist who studied how things work through experiments. He is best known for inventing the Geiger counter, a tool that detects radiation that can change atoms. He also helped conduct the Rutherford scattering experiments, which showed that atoms have a center called a nucleus. Additionally, he worked on the Bothe–Geiger coincidence experiment, which proved that energy remains the same during certain events involving light and particles.
He was the brother of Rudolf Geiger, a scientist who studied weather and climate.
Biography
Johannes Wilhelm Geiger was born on September 30, 1882, in Neustadt an der Haardt, Germany. He was the son of Wilhelm Geiger, an Indologist and professor at the University of Erlangen.
In 1902, Geiger began studying physics and mathematics at the University of Erlangen. He earned his Ph.D. in 1906 under Eilhard Wiedemann, with a thesis about electric discharge in gases.
After completing his Ph.D., Geiger received a scholarship to the University of Manchester, where he worked as an assistant to Arthur Schuster. In 1907, after Schuster retired, Geiger worked with Ernest Rutherford. In 1908, Geiger and Ernest Marsden conducted the famous Geiger–Marsden experiment, also known as the "gold foil experiment." This experiment helped scientists understand how alpha particles behave and led Rutherford to study the structure of atoms. Geiger became a member of the Manchester Literary and Philosophical Society on November 29, 1910.
In 1911, Geiger and John Mitchell Nuttall discovered the Geiger–Nuttall law, which contributed to the development of Rutherford’s atomic model.
In 1912, Geiger became head of radiation research at the Physikalisch-Technische Reichsanstalt (now the Physikalisch-Technische Bundesanstalt) in Charlottenburg. There, he worked with James Chadwick and Walther Bothe, both later Nobel Prize winners. His work was interrupted when he served in the German military as an artillery officer from 1914 to 1918 during World War I.
In 1924, Geiger and Bothe conducted the Bothe–Geiger coincidence experiment, which confirmed the Compton effect. This research helped Arthur Compton win the 1927 Nobel Prize in Physics. Bothe was awarded the Nobel Prize in Physics in 1954 for this work, after Geiger’s death.
In 1925, Geiger began teaching at the University of Kiel. In 1928, he and his student, Walther Müller, developed the Geiger–Müller tube. This device could detect alpha, beta, and gamma particles and became the basis for the Geiger counter. Geiger received the Hughes Medal in 1929 for this invention.
In 1929, Geiger was appointed Professor of Physics and Director of Research at the University of Tübingen. There, he first observed a cosmic ray shower. In 1936, he joined Technische Hochschule Berlin (now Technische Universität Berlin), where he studied cosmic rays, nuclear fission, and artificial radiation until his death in 1945.
From 1939 onward, Geiger was part of the Uranium Club, a German group researching nuclear weapons during World War II. The group split in 1942 when members believed nuclear weapons would not end the war.
Although Geiger signed a petition opposing the Nazi government’s interference with universities, he did not support his colleague Hans Bethe when Bethe was fired for being Jewish.
Geiger survived the Battle of Berlin and the Soviet occupation in April and May 1945. A few months later, he moved to Potsdam, where he died on September 24, 1945.
References
- Geiger, H. and Müller, W. (1928) "Das Elektronenzählrohr" (The electron counting tube), Physikalische Zeitschrift , 29 : 839-841.
- Geiger, H. and Müller, W. (1929) "Technische Bemerkungen zum Elektronenzählrohr" (Technical notes on the electron counting tube), Physikalische Zeitschrift , 30 : 489-493.
- Geiger, H. and Müller, W. (1929) "Demonstration des Elektronenzählrohrs" (Demonstration of the electron counting tube), Physikalische Zeitschrift , 30 : 523 ff.