June 24 marked the 100th birthday of Victor F. Hess, the discoverer of cosmic radiation. The Austrian-born scientist received the Nobel Prize in physics in 1936 with Carl Anderson of the California Institute of Technology, who discovered the positron. When he died in 1964, Hess had more than 150 articles and publications to his credit.
In 1910, while a lecturer at the University of Vienna, Hess launched an unusual series of experiments to measure the conductivity of air. He made 10 balloon ascents, half of these at night. On the basis of these experiments, he concluded that “radiation of very high penetrating power enters our atmosphere from above.” One ascent made during a solar eclipse proved that the sun could not be the main source of cosmic rays.