Austrian-born US physicist who was awarded the Nobel Prize for Physics in 1936 for his discovery of cosmic rays.
The son of a forester, Hess was educated at the University of Graz, where he obtained his PhD in 1906. Hess worked at the newly founded Institute for Radium Research in Vienna from 1910 until 1919, when he was appointed to the chair of physics at the University of Vienna. In 1938 Hess, as a Roman Catholic, was summarily dismissed from his post by the invading Nazis and he emigrated to the USA. He was naturalized in 1944 and became professor of physics at Fordham University, New York, from 1938 until his retirement in 1956.
When Hess joined the radium institute in 1910 he became interested in the source of penetrating ionizing radiation that appeared to occur on the surface of the earth. Initially it was thought to come from the earth and consequently it was assumed that its effect would fall off with increasing altitude. Earlier attempts to confirm this conjecture proved inconclusive. In 1911, therefore, Hess made a number of balloon ascents with his measuring instruments, including one to a height of over 5000 metres. He found that there was an initial decrease in ionization up to a height of about 150 metres, but thereafter activity increased markedly with altitude. As the same effect was observed at night, the source of the radiation could not be attributed to the sun. Hess concluded that the radiation came from outside the solar system and it later became known as cosmic radiation. This subject continued to absorb him for the rest of his scientific life.
Subjects: Science and Mathematics.