Victor Hess

It’s the birthday of Victor Hess, who was born in 1883 in Peggau, Austria. Hess studied physics at the University of Graz. The discovery of radioactivity in 1896 led to the detection of ionizing radiation in the environment. Hess, who was working at Vienna’s Radium Institute, became interested in the phenomenon. At first, the source was presumed to be radioactive elements in the ground. However, that theory could not explain why the radiation level increased with height. By carrying radiation detectors aboard balloons, Hess showed that the radiation level dramatically increases at high altitude. By making measurements during a solar eclipse, he proved that the Sun was not the source. He wrote in 1912: “The results of my observation are best explained by the assumption that a radiation of very great penetrating power enters our atmosphere from above.” Hess had discovered cosmic rays. He was awarded the 1936 Nobel physics prize for the discovery.

Date in History: 24 June 1883