Ludwig Boltzmann
In 1869 at age 25, he was appointed full professor of mathematical physics at the University of Graz. In 1869 he spent several months working with Robert Bunsen and Leo Königsberger at Heidelberg . In 1871 he worked with Gustav Kirchhoff and Hermann von Helmholtz in Berlin. In 1873 Boltzmann went to the University of Vienna as a professor of mathematics and stayed there until 1876.