Cosmic Rays

An Energetic Cosmic Ray

Theodor Wulf 1909
Measured more radioactivity at top of Eiffel Tower than at its base
Victor Hess 1912
Balloon flights showed more radioactivity the higher you flew
Balloon flights during a solar eclipse ruled out solar source
Jacob Clay 1927
Intensity varies with latitude, hence charged particles
Bruno Rossi 1930
Greater intensity from West, hence positive charge
90% H, 9% He, 1% heavier nuclei
Produce "showers" of secondary particles
Possibly define lightning channels
Grave threat to astronauts