Heinrich Rubens (30.03 1865-17.07.1922) was a German experimental physicist and a member of the Berlin Academy of Sciences (1907). Born in Wiesbaden. Graduated from the University of Berlin (1889) and worked as an assistant at the university's Physical Institute. From 1896 he was professor and director of the physics laboratory of the Higher Technical School in Charlottenburg, and from 1906 professor at the University of Berlin and director of the Physical Institute.
His work was in the field of the theory of radiation, electricity and optics. He developed the method of infrared “residual rays” (1897–98). He measured radiation in the infrared spectrum and greatly extended the range of it accessible to observation (to 61 μm). He gave experimental confirmation of the Helmholtz–Ketteler dispersion theory (1894). Together with E. Hagen he measured the reflectivity of metals (1900–02), in particular in the region of long wavelengths, and showed that the data agreed with Maxwell's electromagnetic theory of light and with experimental metal optics, thereby helping to establish the theory. Together with F. Kurlbaum (independently of O. Lummer and E. Pringsheim) he showed (1900) that Wien's radiation law is not confirmed in the region of long wavelengths. The analysis of these measurements of the radiation spectrum led M. Planck to establish the law of thermal radiation using the quantum of action. In 1900–01, with Kurlbaum, he proved the validity of the formula proposed by Planck for the distribution of energy in the spectrum of black-body radiation and confirmed the Rayleigh law of thermal radiation for long wavelengths. He designed a number of instruments, in particular the bolometer, a highly sensitive mirror galvanometer, the thermopile (1897) and others.