While this hot gas can be seen, the actual dark matter it masks cannot.The existence of dark matter is known from its gravitational effects on visible matter, radiation, and the large-scale structure of the universe.Although dark matter doesn't absorb, emit or scatter light, the researchers inferred its distribution by charting how its gravitational influence altered the paths of light zooming past.Analysis of the clumpiness of the dark matter in the maps will also allow scientists to probe the nature of the mysterious dark energy, believed to be causing the expansion of the universe to speed up.We used to think that dark matter sits around, minding its own business, " said Dr Richard Massey, a Royal Society research fellow and member of Durham University's Institute for Computational Cosmology.Because dark matter does not reflect, absorb or emit light, it can only be traced indirectly by, such as by measuring how it warps space through gravitational lensing, during which the light from a distant source is magnified and distorted by the gravity of dark matter.They say that the dark matter has scattered due to the gravitational force and an interaction with the photons and neutrinos in the young universe.Kevork Abazajian, Nicolas Canac, Shunsaku Horiuchi and Manoj Kaplinghat analyzed data from NASA's space-borne Fermi Gamma-ray Space Telescope and found that only a narrow range of dark matter models can produce an excess of gamma rays coming from the Milky Way.A detector attached to the International Space Station has so far failed to find any dark matter either.They seem to bear the signature of collisions between atoms of dark matter, the mysterious "stuff" that cannot be seen or detected directly but which binds the cosmos together.After nine years of searching, detectors buried 2, 000ft underground in an old US iron mine registered two "hits" by what could turn out to be dark matter particles.If particles of dark matter somehow could be detected, theoretical advances in physics and astronomy over the past several decades would gain evidentiary support.
What Is Dark Matter
Dark Matter or Modified Gravity? - Stacy McGaugh
How is matter defined?
Anything that has mass and occupies space.
or.. anything which can be observed by our five senses.