Cosmic rays

A gold-leaf electroscope detects energetic radiation by allowing the leaves to come together when ionization occurs. When this instrument was sent up into the atmosphere, the leaves came up eight times faster at large heights versus ground level, suggesting a source of radiation from the cosmos.
 Victor Franz Hess Austria 1911 Cosmic rays

A gold-leaf electroscope detects energetic radiation by allowing the leaves to come together when ionization occurs. When this instrument was sent up into the atmosphere, the leaves came up eight times faster at large heights versus ground level, suggesting a source of radiation from the cosmos.