Wilhelm Wien (13.01.1864-30.08.1928) was a German physicist and a corresponding member of the Berlin Academy of Sciences. He was born in Gaffken. He graduated from the University of Berlin (1886). In 1890-1902 he was assistant to H. Helmholtz at the Physikalisch-Technische Reichsanstalt (Berlin), in 1900—20 he was professor at the University of Würzburg and in 1920—28 at the University of Munich.
His research was in the field of the theory of thermal radiation, optics, thermodynamics, hydrodynamics and the study of electric discharges in gases. In 1893 he extended the concepts of temperature and entropy to thermal radiation and showed that, as the temperature rises, the maximum of the radiation in the spectrum of a black body shifts towards shorter wavelengths (Wien's displacement law).
In 1895, together with O. Lummer, he developed G. Kirchhoff's ideas on the black body and showed that it can be realised as a cavity with internal mirror walls and a narrow aperture. In 1896, starting from classical ideas, he derived the law of the distribution of energy in the spectrum of a black body (Wien's radiation law). As soon became clear, however, the formula of Wien's radiation law proved to be correct only in the case of short wavelengths. These two laws of Wien's played a considerable part in the development of quantum theory (Nobel Prize, 1911).
In 1902 he established the deflection of canal rays in electric and magnetic fields, measured the ratio of their charge to their mass and also proved that their charge is positive. He studied electrical conductivity in metals (in 1913 he came to the conclusion that the velocity of free electrons in metals does not depend on temperature), and cathode rays and X-rays. In 1907 he measured the wavelength of X-radiation.