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Dark matter is matter that cannot be detected by electromagnetic radiation. Hence the dark. It is postulated to exist to explain how clusters and superclusters of galaxies formed after the big bang. Data from galaxy rotation curves indicate that around 90% of the mass of a galaxy cannot be seen. It can only be detected by its gravitational effect. In addition to hot dark matter, there are several other types of dark matter postulated to exist: baryonic dark matter and cold dark matterCold dark matter (or CDM is a refinement of the big bang theory that contains the additional assumption that most of the matter in the Universe consists of material which cannot be observed by its electromagnetic radiation and hence is dark while at the s
Hot dark matter cannot explain how individual galaxies formed from the big bang. The microwave background radiation as measured by the COBECosmic Background Explorer Organization NASA Major Contractors Goddard Space Flight Center Mission Type Cosmology Satellite of Earth Launch November 18, 1989 on Delta I Mission Duration~4 years Mass2270 kg NSSDC ID1989-089A Webpagehttp://lambda. gov/produ satellite is very smooth and fast moving particles cannot clump together on this small scale from such as smooth initial clumping. To explain small scale structure in the UniverseAlternate uses: See Universe (disambiguation In the first half of the 20th century, the word universe was used to mean the whole spacetime continuum in which we exist, together with all the energy and matter within it. Attempts to understand the universe it is necessary to invoke cold dark matter. Hot dark matter therefore is nowadays always discussed as part of a mixed dark matter theory.