Victor Franz Hess
Born: 24 June 1883, Peggau, Austria
Died: 17 December 1964, Mount Verno, NY, USA
Affiliation at the time of the award: Innsbruck University, Innsbruck, Austria
Prize motivation: "for his discovery of cosmic radiation"
Field: astrophysics, cosmic radiation
Prize share: 1/2
In reactions between radiation and atoms, charged ions are often produced. Victor Hess, using balloons, measured in 1912 atmospheric ionisation as function of altitude. To his surprise he found that the ionisation first decreased, but later for the highest altitudes, increased strongly. He concluded that a penetrating radiation is evident on the earth from outside. He could also exclude that this radiation emanates from the sun. Cosmic rays were discovered.