Cosmic rays were long used as a source of high-energy particles in the study of nuclear reactions. They were so named in 1925 by R. A. Millikan, who did extensive research on them. Since then much pertinent information has been collected that have been of use in studying the chemical composition of the universe, but the origin of cosmic rays remains a mystery. However, when they react with interstellar gases, the result is a gamma ray that can be traced back. Spacecraft results indicate that many of the gamma rays appear to come from the direction of supernova remnants.
Cosmic rays play a significant role in the natural mutation and evolution of life on earth.