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

Their aim is to understand why some cosmic ray sources emit neutrinos while others do not, as well as pinpoint where and how those neutrinos are produced.

From Science Daily • Nov. 26, 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

"We have to go through all the underlying hypotheses regarding acceleration mechanisms and environmental conditions in order to convert the absence of gamma rays into an upper limit for cosmic ray production."

From Science Daily • Apr. 16, 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