Karl Wilhelm Meissner (December 15, 1891 in Reutlingen, Württemberg – April 13, 1959 on a cruise ship sailing to Europe) was a German-American physicist specializing in hyperfine spectroscopy.

[2] In 1916 he became an assistant to Edgar Meyer[3] at the University of Zurich, under whom he completed his Habilitation, in 1918, with the Habilitationsschrift title Untersuchungen des Neonspektrums.

After the retirement of Martin Brendel and with the support of Richard Wachsmuth, Meissner was appointed ordinarius professor of astronomy and director of the University’s observatory.

To reduce these broadening mechanism, Meissner, with K. F. Luft and independently of R. Minkowski and H. Bruck, in 1935, developed the technique of observing particle beams perpendicular to their direction of flow.

[6] With this technique, Meissner could investigate the hyperfine structure of spectra, which are due to the magnetic moment of the atomic nuclei.

From three offers in the United States, Meissner selected a position as assistant professor at Worcester Polytechnic Institute in November of that year.

[5] On 9 April 1959, Meissner sailed from New York City for Europe to visit his sister and niece, visit the Bureau International des Poids et Mesures (International Bureau of Weights and Measures), teach in the summer semester at the Christian-Albrechts University of Kiel, and attend an interferometry conference in London.