Dark Matter

In astronomy and cosmology, dark matter is a type of matter hypothesized to account for a large part of the total mass in the universe. Dark matter cannot be seen directly with telescopes; evidently it neither emits nor absorbs light or other electromagnetic radiation at any significant level. Instead, its existence and properties are inferred from its gravitational effects on visible matter, radiation, and the large scale structure of the universe. Dark matter is estimated to constitute 84% of the matter in the universe and 23% of the mass-energy.

Dark matter came to the attention of astrophysicists due to discrepancies between the mass of large astronomical objects determined from their gravitational effects, and the mass calculated from the "luminous matter" they contain; such as stars, gas and dust. It was first postulated by Jan Oort in 1932 to account for the orbital velocities of stars in the Milky Way and Fritz Zwicky in 1933 to account for evidence of "missing mass" in the orbital velocities of galaxies in clusters. Subsequently, other observations have indicated the presence of dark matter in the universe, including the rotational speeds of galaxies, gravitational lensing of background objects by galaxy clusters such as the Bullet Cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies. According to consensus among cosmologists, dark matter is composed primarily of a new, not yet characterized, type of subatomic particle. The search for this particle, by a variety of means, is one of the major efforts in particle physics today.

Although the existence of dark matter is generally accepted by the mainstream scientific community, several alternative theories have been proposed to try to explain the anomalies for which dark matter is intended to account.

Read more about Dark MatterOverview, Baryonic and Nonbaryonic Dark Matter, Observational Evidence, History of The Search For Its Composition, Detection, Alternative Theories, Popular Culture

Other articles related to "dark matter, matter, dark":

Light Dark Matter
... In astronomy and cosmology, light dark matter refers to dark matter Weakly interacting massive particle (WIMP) candidates with masses less than 1 GeV ... These particles are heavier than warm dark matter and hot dark matter, but are lighter than the traditional forms of cold dark matter ... The Lee-Weinberg bound limits the mass of the favored dark matter candidate, WIMPs, that interact via the weak interaction to GeV ...
Mirror Photon - Observational Effects of Mirror Matter
... If mirror matter is present in the universe with sufficient abundance then its gravitational effects can be detected ... Because mirror matter is analogous to ordinary matter, it is then to be expected that a fraction of the mirror matter exists in the form of mirror galaxies ... What if mirror matter does exist but has (almost) zero abundance? Like magnetic monopoles, mirror matter could have been diluted to unobservably low ...
Dark Matter - Popular Culture
... Main article Dark matter in fiction Mention of dark matter is made in some video games and other works of fiction ... are often inconsistent with the properties of dark matter proposed in physics and cosmology ...
Dark Energy - Implications For The Fate of The Universe
... the expansion was decelerating, due to the attractive influence of dark matter and baryons ... The density of dark matter in an expanding universe decreases more quickly than dark energy, and eventually the dark energy dominates ... when the volume of the universe doubles, the density of dark matter is halved but the density of dark energy is nearly unchanged (it is exactly constant in the case of a cosmological ...
Light Dark Matter - See Also
... Axion Axion Dark Matter Experiment Dark matter halo Minimal Supersymmetric Standard Model Neutralino Scalar field dark matter Weakly interacting massive particles ...

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