cosmic ray

noun

: a stream of atomic nuclei of extremely penetrating character that enter the earth's atmosphere from outer space at speeds approaching that of light

Examples of cosmic ray in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Neutrinos hint at where cosmic rays come from Every second, more than 10,000 high-energy particles – protons and atomic nuclei – rain down from space on every square meter of the Earth’s atmosphere. — Tyce Deyoung, The Conversation, 6 Oct. 2026 Natural cosmic ray muography yields only about 1 muon per square centimeter per second. — Mrigakshi Dixit, Interesting Engineering, 2 Oct. 2026 This celestial shield keeps harmful solar wind, cosmic rays and radiation at bay, preventing the atmosphere from being stripped away. — Jacopo Prisco, CNN Money, 29 Sep. 2026 For nearly 50 years, the instrument has provided constant measurements on the ion, electron and cosmic ray environment in deep space. — Tariq Malik, Space.com, 5 Sep. 2026 See All Example Sentences for cosmic ray

Word History

First Known Use

1925, in the meaning defined above

Time Traveler
The first known use of cosmic ray was in 1925

Rhymes for cosmic ray

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Browse Nearby Words

cosmic radiation
cosmic ray
cosmic-ray shower
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Cite this Entry

“Cosmic ray.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cosmic%20ray. Accessed 14 Oct. 2026.

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Kids Definition

cosmic ray

noun
: a stream of atomic nuclei of extremely penetrating character that enter the earth's atmosphere from outer space at speeds approaching that of light

More from Merriam-Webster on cosmic ray

Britannica.com: Encyclopedia article about cosmic ray

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