What are cosmic rays?

(Lansing State Journal, March 10, 1993)

Question submitted by Tara Strom.

Cosmic rays were first discovered by Victor Franz Hess. In 1912 he and two other men took a hydrogen balloon up to a height of 5 kilometers in order to measure changes in atmospheric electricity. What they discovered was strongly penetrating radiation that seemed to be coming from beyond the earth's atmosphere. It took more than forty years for scientists to understand what this radiation was made of and from where it was coming. Twenty-four years after his discovery, Hess was awarded the Nobel Prize.

Cosmic rays are made up of protons, helium nuclei, electrons and other heavier particles produced by stars and other processes occurring throughout the galaxy. Between 1 and 2 pounds of cosmic ray material strike the Earth each day traveling at near the speed of light. The energies of these particles can far exceed the energies that can be reached by any man made particle accelerator.

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