background radiation

noun

Definition of background radiation

: the microwave radiation pervading the universe that exhibits a corresponding blackbody temperature of 2.7 K and that is the principal evidence supporting the big bang theory

called also cosmic background radiation

Examples of background radiation in a Sentence

Recent Examples on the Web The federal helicopter survey was originally supposed to fly above parts of the Bay Area as part of a research project to study background radiation levels. Cynthia Dizikes, SFChronicle.com, "Three SF supervisors, environmental groups seek ouster of health official after Chronicle investigation," 3 Sep. 2020 That means, Martens said, that there’s about a 2 in 10,000 chance that random background radiation produced the signal as opposed to solar axions themselves. Rafi Letzter, Scientific American, "Physicists Announce Potential Dark Matter Breakthrough," 17 June 2020 But all detectors, no matter how well-shielded, experience noise from sources such as background radiation. Daniel Garisto, Scientific American, "Direct Proof of Dark Matter May Lurk at Low-Energy Frontiers," 9 June 2020 Peebles and his colleagues had predicted this background radiation, a result of when the universe, about 400,000 years after the Big Bang, cooled off enough for hydrogen and helium atoms to form. BostonGlobe.com, "“They really, sort of tell us something very essential — existential — about our place in the universe,” Ulf Danielsson, a member of the Nobel committee, said during an interview broadcast on the web.," 9 Oct. 2019 Further such tests, and more refined observations of other cosmological features (such as the remnant microwave background radiation generated when the universe was young), might still someday find flaws in general relativity. Tom Siegfried, Scientific American, "Physicists Probe Validity of Einstein’s Gravity on Cosmic Scales," 21 Jan. 2020 The reactors themselves are being decommissioned, but air dose rates in residential areas have fallen 71 percent to .37 microserviets per hour, within the range of naturally occurring background radiation. Laura Mallonee, Wired, "The Eerie Repopulation of the Fukushima Exclusion Zone," 3 Feb. 2020 For comparison, the World Nuclear Association says background radiation in the natural environment typically exposes people to an average 2.4 mSv a year, while a CT scan of the pelvis results in an effective dose of 10 mSv. Washington Post, "Why Japan’s Radioactive Water May End Up In the Ocean," 18 Oct. 2019 Many readings in the buffer zone were no higher than natural background radiation values. Vincent Carroll, The Denver Post, "Carroll: Should you be worried about that Rocky Flats soil sample? Let’s put it in perspective.," 18 Oct. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'background radiation.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of background radiation

1968, in the meaning defined above

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The first known use of background radiation was in 1968

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Last Updated

7 Sep 2020

Cite this Entry

“Background radiation.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/background%20radiation. Accessed 22 Sep. 2020.

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