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In astrophysics and cosmology, dark matter is hypothetical matter of unknown composition that does not interact with the electromagnetic force to be observed directly, but whose presence can be inferred from gravitational effects on visible matter. Dark matter interacts only with the gravitational force. According to present observations of structures larger than galaxy-sized as well as Big Bang cosmology, dark matter accounts for the vast majority of mass in the observable universe. Fritz Zwicky used it for the first time to declare the observed phenomena consistent with dark matter observations as the rotational speeds of galaxies and orbital velocities of galaxies in clusters, 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. Dark matter also plays a central role in structure formation and galaxy evolution, and has measurable effects on the anisotropy of the cosmic microwave background. All these lines of evidence suggest that galaxies, clusters of galaxies, and the universe as a whole contain far more matter than that which interacts with electromagnetic radiation: the remainder is called the "dark matter component".
Dark matter may be related to supersymmetry. The composition of dark matter is unknown, but may include ordinary and heavy neutrinos, recently postulated elementary particles such as WIMPs and axions, astronomical bodies such as dwarf stars and planets (collectively called MACHOs), and clouds of nonluminous gas.
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The point of this post was to demonstrate that the universe consists primarily of dark (non-luminous) matter, also that this matter is of an exotic non-baryonic form. All the visible matter in the universe is baryonic (including we of course) but the universe contains far more matter which is invisible and non-baryonic.
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