Stefan, Josef 1835-93
Austrian physicist

Born near Klagenfurt, he became Professor of Physics at Vienna University in 1863 after seven years of school-teaching. In 1866 he was appointed director of the Institute for Experimental Physics founded in Vienna by Christian Doppler in 1850. In 1879 he proposed Stefan's law (or the Stefan-Boltzmann law), that the amount of energy radiated from a black body is proportional to the absolute temperature, and he used this law to make the first satisfactory estimate of the Sun's surface temperature. He also designed a diathermometer to measure heat conduction, and worked on the kinetic theory of heat and on the relationship between surface tension and evaporation (1886).