Johannes Stark

Johannes Stark (1874–1957) was a German physicist who discovered the Doppler effect in canal rays and the splitting of spectral lines in electric fields. He received the 1919 Nobel Prize in Physics.

Wilhelm Wien: Wilhelm Wien was a German physicist whose work on thermal radiation and charged particles influenced early atomic physics. Wien supervised Stark’s doctoral research in physics at the University of Munich.
Doppler effect in canal rays: The shift of spectral lines emitted by moving positive ions, used to measure their velocity. Stark observed this effect by comparing light from canal rays moving toward and away from an observer.
University of Munich: A public research university in Munich, founded in 1472 and known as Ludwig Maximilian University since 1802. Stark studied and earned his doctorate there under Wilhelm Wien.
Nazi Germany: The German state under Adolf Hitler’s dictatorship from 1933 to 1945. Stark used his influence within the regime to promote Deutsche Physik.
Arnold Sommerfeld: Arnold Sommerfeld was a German theoretical physicist who developed influential models of atomic structure and quantum theory. Sommerfeld’s account of spectral structure differed from Stark’s interpretation of the hydrogen spectrum.
Stark effect: The shifting or splitting of atomic and molecular spectral lines in an electric field. This electric-field-induced spectral splitting is Stark’s best-known discovery.
University of Göttingen: A public research university in Göttingen, Germany, founded in 1737. Stark held a professorship in physics there early in his academic career.
German Physics Society: The principal professional society for physicists in Germany, founded in 1845. Stark’s political campaign brought him into conflict with the society’s scientific leadership.
Max Planck: Max Planck was a German physicist whose introduction of energy quanta helped establish quantum theory. Planck publicly criticized Stark’s political attacks on modern physics and its practitioners.
Canal rays: Streams of positive ions produced in a gas-discharge tube and observed through perforated cathodes. Their moving ions provided the light source for Stark’s Doppler-effect measurements.

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Karl SchwarzschildRelated: Stark and Schwarzschild both investigated how radiation and fields shape spectral observations.