cosmic ray

American  

noun

Physics.

1. a radiation of high penetrating power that originates in outer space and consists partly of high-energy atomic nuclei.

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cosmic ray Scientific  

1. 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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Etymology

Origin of cosmic ray

An Americanism dating back to 1920–25

Example Sentences

Black hole jet systems linked directly to the cosmic ray "knee"

From Science Daily • Nov. 16, 2025

This resolves a long-standing tension in cosmic ray research: while supernova remnants are known to produce cosmic rays, both data and theory suggest they cannot account for the energies seen at and above the "knee."

From Science Daily • Nov. 16, 2025

In 1948, Bristol's cosmic ray physics team, led by Professor Cecil Powell, were hunting for new fundamental particles.

From BBC • Jul. 23, 2024

Inspired by his doctoral adviser, John A. Simpson, Dr. Stone performed his first cosmic ray experiments in 1961 while working on Discover 36, an Air Force spy satellite.

From New York Times • Jun. 14, 2024

“Some of the cosmic ray enthusiasts are very likely to urge that nature has furnished us with particles of extremely high energies,” he observed.

From "Big Science" by Michael Hiltzik