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

The intricate structure of the proton spectrum suggests that PeV cosmic rays are largely produced by "new sources" such as micro-quasars, which can accelerate particles to significantly higher energies than supernova remnants.

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

Carbon 14 is continually being generated in the atmosphere by cosmic rays.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond