- a radiation of high penetrating power that originates in outer space and consists partly of high-energy atomic nuclei.
Origin of cosmic ray
An Americanism dating back to 1920–25
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for cosmic ray
And he pointed to the cosmic-ray skiagraph of the Moon on the curved glass dome overhead.
- A ray of radiation of extraterrestrial origin, consisting of one or more charged particles such as protons, alpha particles, and larger atomic nuclei. Cosmic rays entering the atmosphere collide with atoms, producing secondary radiation, such as pions, muons, electrons, and gamma rays. Cosmic rays (and secondary radiation) can be easily seen in a cloud chamber.
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