Ernst J. L. Gehrcke (1 July 1878 in Berlin – 25 January 1960 in Hohen-Neuendorf) was a German experimental physicist. He was director of the optical department at the Reich Physical and Technical Institute. Concurrently, he was a professor at the University of Berlin. He developed the Lummer–Gehrcke method in interferometry and the multiplex interferometric spectroscope for precision resolution of spectral-line structures. As an anti-relativist, he was a speaker at an event organized in 1920 by the Working Society of German Scientists. He sat on the board of trustees of the Potsdam Astrophysical Observatory. After World War II, he worked at Carl Zeiss Jena, and he helped to develop and become the director of the Institute for Physiological Optics at the University of Jena. In 1949, he began work at the German Office for Materials and Product Testing. In 1953, he became the director of the optical department of the German Office for Weights and Measures. Education Gehrcke studied at the Friedrich-Wilhelms-Universität (today, the Humboldt-Universität zu Berlin) from 1897 to 1901. He received his doctorate under Emil Warburg in 1901. Career In 1901, Gehrcke joined the Physikalisch-Technische Reichsanstalt (PTR, Reich Physical and Technical Institute, after 1945 renamed the Physikalisch-Technische Bundesanstalt). In 1926, he became the director of the optical department, a position he held until 1946. Concurrent with his position at the PTR, he was a Privatdozent at the Friedrich-Wilhelms-Universität from 1904 to 1921 and an außerordentlicher Professor (extraordinarius professor) from 1921 to 1946. After the close of World War II, the University was in the Russian sector of Berlin. In 1946, Gehrcke worked at Carl Zeiss AG in Jena, and he helped to develop and become the director of the Institute for Physiological Optics at the Friedrich-Schiller-Universität Jena. In 1949, he went to East Berlin to the Deutsches Amt für Materialprüfung (German Office for Materials and Product Testing). In 1953, he became the director of the optical department of the Deutsches Amt für Maß und Gewicht (DAMG, German Office for Weights and Measures) in East Berlin, the East German equivalent to the West German Physikalisch-Technische Bundesanstalt (Federal Physical and Technical Institute). Gehrcke contributed to the experimental techniques of interference spectroscopy (interferometry), physiological optics, and the physics of electrical discharges in gases. In 1903, with Otto Lummer, he developed the Lummer–Gehrcke method in interferometry. In 1927, with Ernst Gustav Lau, he developed the multiplex interferometric spectroscope for precision resolution of