Dark matter

Article By:

Spergel, David N. Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey.

Last reviewed:August 2022

DOI:https://doi.org/10.1036/1097-8542.800520

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• Dark matter, published February 2019:Download PDF Get Adobe Acrobat Reader
• Dark matter, published June 2014:Download PDF Get Adobe Acrobat Reader

Particles or objects that exert a gravitational force but do not emit any detectable visible light or other electromagnetic radiation of any kind. Dark matter is the dominant form of matter in our Galaxy and in the universe, estimated to comprise approximately 85% of all matter. In terms of the total composition or energy density of the universe, dark matter is estimated to account for about 25%, regular matter is estimated at about 5%, and the remaining 70% is attributed to dark energy. Astronomers have inferred the presence of dark matter through its gravitational effects and have shown that dark matter is not composed of ordinary particles. Physicists have suggested several plausible candidates for dark matter; ongoing and planned experiments are capable of detecting these new particles. There are controversial claims of dark-matter detection. If our understanding of gravity as explained by German-born U.S. theoretical physicist Albert Einstein’s theory of general relativity is correct, as more than a century’s-worth of experiments have verified with ever-increasing precision, then dark matter must exist. However, it is possible that relativity is not correct, and a new physics paradigm will be needed to solve the mystery of dark matter. See also: Dark energy; Elementary particle; Gravity; Matter; Relativity; Universe

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