The concept of dark matter arose as a solution to a problem that has been puzzling astronomers for decades. Galaxies, when observed, rotate at a much faster rate than is expected for the estimated mass they contain..... Dark Energy, Dark Matter New Kind of Dark Matter Could Form 'Dark Atoms' Dark matter is the name we give to matter we can not observe directly, and that appears to be made up of something other than baryons. http://news.discovery.com/space/galaxies/hubble-space-telescope-latest-cosmic-pictures-130129.htm Dark matter is thought to make up 80 percent of all matter in the Universe, the rest is “baryonic matter” — i.e. the stuff we’re made of. But the vast majority of matter is locked in an invisible component of matter. As the moniker suggests, dark matter is dark; it doesn’t interact with electromagnetic radiation. However, dark matter still carries mass that has a gravitational effect on space-time and through indirect means we can detect its gravitational presence. .. mm dm detection Snowmass Working Group Reports Contributed Papers Submitted to the Snowmass 2013 Study <br /> http://www.astro.caltech.edu/~golwala/talks/20050521CaltechSeminarDay.pdf The Standard Model (SM) of particle physics fails to explain dark matter and why matter survived annihilation with antimatter following the Big Bang. Extensions to the SM, such as weak-scale Supersymmetry, may explain one or both of these phenomena by positing the existence of new particles and interactions that are asymmetric under time-reversal (T).