Victor Hess (1883-1964), Austrian-American physic- ist and discoverer of cosmic rays. Educated at Graz, Hess worked on radioactivity at Vienna until 1920. He was interested in locating the source of background radiation which causes ionization of air even in the absence of radioactive materials. Hess proved that the radiation comes from space. His experiments in 1911-12 with balloon flights showed ionization to be four times greater at an altitude of 5000m than at ground level. American physicist Robert Millikan later named the high- energy particles responsible for the radiation cosmic rays. For the discovery of cosmic rays, Hess received the Nobel Prize for physics in 1936.