Hot dark matter is a form of dark matter, which consists of particles that travel with relativistic velocities. The best candidate for hot dark matter is the neutrino. Neutrinos have very small mass, and do not partake in two of the four fundamental forces, the electromagnetic interaction, and strong interaction. They do interact with the weak nuclear force, and gravity, and are extremely difficult to detect. A few projects, such as the Super-Kamiokande neutrino observatory, in Gifu, Japan are currently studying these neutrinos. In cosmology, dark matter refers to matter particles, of unknown composition, that do not emit or reflect enough electromagnetic radiation to be detected directly, but whose presence can be inferred from gravitational effects on visible matter such as stars and galaxies. ... For a non-technical introduction to the topic, please see Introduction to Special relativity. ... The neutrino is an elementary particle. ... Electromagnetic interaction is a fundamental force of nature and is felt by charged leptons and quarks. ... The strong interaction or strong force is today understood to represent the interactions between quarks and gluons as detailed by the theory of quantum chromodynamics (QCD). ... The weak nuclear force or weak interaction is one of the four fundamental forces of nature. ... Gravity is a force of attraction that acts between bodies that have mass. ... Super-Kamiokande, or Super-K for short, is a neutrino observatory in Japan. ...

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. Electromagnetic radiation can be conceptualized as a self propagating transverse oscillating wave of electric and magnetic fields. ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ... Superclusters are large groupings of smaller galaxy groups and clusters, and are among the largest structures of the cosmos. ... This article is about a celestial body. ... According to the Big Bang theory, the universe emerged from an extremely dense and hot state (bottom). ... The galaxy rotation problem is the discrepancy between the observed rotation speeds of matter in the disk portions of spiral galaxies and the predictions of Newtonian dynamics considering the luminous mass. ... Gravity is a force of attraction that acts between bodies that have mass. ...

Hot dark matter cannot explain how individual galaxies formed from the big bang. The microwave background radiation as measured by the COBE satellite is very smooth and fast moving particles cannot clump together on this small scale from such a smooth initial clumping. To explain small scale structure in 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. WMAP image of the CMB anisotropy,Cosmic microwave background radiation(June 2003) The cosmic microwave background radiation (CMB) is a form of electromagnetic radiation that fills the whole of the universe. ... The Cosmic Background Explorer (COBE), also referred to as Explorer 66, was the first satellite built dedicated to cosmology. ... The deepest visible-light image of the cosmos, the Hubble Ultra Deep Field. ...

External links

• Hot dark matter by Berkeley
• Dark Matter