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{{dablink|Not to be confused with [[Dark energy]] or [[Dark fluid]]. For other uses, see [[Dark Matter (disambiguation)]]}}
{{Physical cosmology|cTopic=Components}}
In [[astronomy]] and [[physical cosmology|cosmology]], '''dark matter''' is a [[theoretical substance]] of unknown composition suggested as the cause for a ubiquitous [[mass]]-[[gravitation]]al phenomenon observed at [[astrophysics|astrophysical]] scales.
InEvidence [[astronomy]]for andthe [[physicalpresence cosmology|cosmology]],of '''dark matter''' is [[matter]] that is inferred to existcomes from [[gravity|gravitational]] effects on visible matter and background radiation, but—effects attributable to [[matter]] (ie. a substance with [[mass]]) —but which is undetectablenot evident as "visible matter" through the normal detection byof [[blackbody spectrum|emitted]] or [[scattering|scattered]] [[electromagnetic radiation]].<ref>Mark J Hadley (2007) "[http://arxiv.org/PS_cache/gr-qc/pdf/0701/0701100v1.pdf Classical Dark Matter]"</ref> Its existence was hypothesized to account for discrepancies between measurements of the mass of [[galaxy|galaxies]], [[galaxy cluster|clusters of galaxies]] and the entire universe made through [[dynamics (mechanics)|dynamical]] and [[general relativity|general relativistic]] means, and measurements based on the mass of the visible "luminous" matter these objects contain: [[star]]s and the gas and dust of the [[interstellar medium|interstellar]] and [[Outer space|intergalactic]] media. According to observations of structures larger than [[galaxies]], as well as [[big bang|Big Bang cosmology]] interpreted under the "Friedmann equations" and the "FLRW metric", dark matter accounts for 23% of the [[Mass-energy equivalence|mass-energy density]] of the [[observable universe]], while the ordinary matter accounts for only 4.6% (the remainder is attributed to [[dark energy]]).<ref>{{cite web
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