Cosmic ray

Cosmic rays can loosely be defined as radiation consisting of energetic particles originating outside of the Earth. The composition of such rays includes electrons, protons, gamma rays, and atomic nuclei from a large region of the periodic table. Though neutrons are not stable, the relativistic time dilation may allow them to reach Earth at very high energies.

References

• Pierre Auger Observatory: the largest cosmic ray observatory in the world, in Argentina, with a twin coming in Colorado
• 1 Introduction to Geomagnetically Trapped Radiation by Martin Walt 1994
• Cosmic Rays by A. M. Hillas, 1972 Pergamon Press, Oxford. A good overview of the history and science of cosmic ray research including reprints of seminal papers by Hess, Anderson, Auger and others.
• Cosmic Rays by B. Rossi, 1964 McGraw-Hill, New York.