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

See Examples For:

cosmic ray

Nearly a mile of rock above the experiment blocks much of the cosmic ray radiation arriving from space.

From Science Daily ● Sep. 4, 2026

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

Understanding the full picture requires precise measurements of the energy spectra of different cosmic ray species and their individual "knees."

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

“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