cosmic rays

British  

plural noun

1. Also called: cosmic radiation.  radiation consisting of particles, esp protons, of very high energy that reach the earth from outer space

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cosmic rays Cultural  

1. Elementary particles, mainly protons, that are produced by the sun and other stars and then strike the upper atmosphere of the Earth. Some of these particles are absorbed, some help form the Van Allen belt, and some reach the Earth's surface, where they form a part of the background radiation that constantly surrounds us.

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Example Sentences

Earth's magnetosphere offers some protection against radioactive cosmic rays and solar particles to the orbiting ISS, but no such cover on the Moon.

From Barron's • Apr. 10, 2026

The visionaries of the early Space Age didn’t worry much about solar radiation, coronal mass ejections, galactic cosmic rays, psychological stress from isolation, and cost-benefit ratios.

From Slate • Dec. 9, 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

But when the Cold War propelled the U.S. to seek technological dominance on Earth and beyond, it was JPL that developed the U.S.’ first successful satellite, Explorer 1, designed to study cosmic rays.

From Los Angeles Times • Oct. 19, 2025

Mesons had been found only in cosmic rays, which made them the natural quarry of high-energy physicists.

From "Big Science" by Michael Hiltzik