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The origin of cosmic rays

Cosmic rays are secondary particles

Most of the cosmic rays that hit the Earth are very fast moving protons emitted from the Sun and other stars.  They collide with the nuclei of air molecules in the upper atmosphere causing a shower of secondary particles.

Try Why Do Astronauts Float by Julian Hamm

One of the more common is a type of heavy electron called a muon.  So the background cosmic radiation is really the shower of secondary particles formed in the upper atmosphere.

back to Lesson 4: Background Radiation