Dark Matter Essay -- essays research papers

There is perhaps no current trouble of greater importance to astrophysics and cosmology than that of "dark government issue". The controversy, as the secernate implies, is centered on the notion that in that location may exist an fantastic amount of takings in the instauration that cannot be detected from the heat that it emits. The evidence of dark matter is from the motions of astronomical objects, specific entirelyy stellar, galactic, and galaxy flock/supercluster observations. The basic argument is that if we measure velocities in some region, then there has to be enough cumulus there for gravity to stop all the objects from flying apart. When such velocity measurements are done on colossal scales, it turns out that the amount of inferred mass is much more than can be explained by the luminous mass. Hence we infer that there is non-luminous matter in the Universe, i.e. there is dark matter. Dark matter has important consequences for the evolution of the Univer se. concord to standard cosmological theory, the Universe must conform to one of triple possible types open, flat, or closed. A parameter known as the "mass density" - that is, how much matter per unit volume is contained in the Universe - determines which of the three possibilities applies to the Universe. In the case of an open Universe, the mass density (denoted by the Greek letter ezed) is less than unity, and the Universe is predicted to expand forever. If the Universe is closed, Omega is greater than unity, and the Universe will eventually stop its expansion and recollapse ski binding upon itself. For the case where Omega is exactly equal to one, the Universe is delicately equilibrize between the two states, and is said to be "flat". Dark matter candidates are usually split into two broad categories, with the second kinsperson being further sub-divided baryonic and bon-baryonic. Then, under non-baryonic, hot dark matter (HDM) and common frigidness dark ma tter (CDM) are its types. Depending on their respective masses and speeds, CDM candidates thrust relatively large mass and travel at slow speeds (hence "cold"), while HDM candidates include minute-mass, rapidly moving (hence "hot") particles.As booster cable possible candidates for baryonic dark matter, there are black holes (large and small), brown dwarfs (stars also cold and faint to radiate), sun-size MACHOs, cold gas, dark galaxies and dark clusters, ... ...e seeking them in a Stanford laboratory by watching for radiation as they energise crystals of germanium in a detector, but they creatent detected any yet. short they will try an even more exotic search by moving their equipment to an old iron mine 2,400 feet deep in northern Minnesota where one or two WIMPs, if they really exist, might very(prenominal) occasionally make their existence known. The detectors are hockey puck-sized superconducting crystals of germanium and silicon. These polished crysta ls are cooled to about 500 degrees below zero. A particle strike a detector disturbs the molecular structure of the crystal and registers as a slight temperature increase. Because WIMPs easily goodby through most matter, they can pass through the shields and register a signal. To date, the detectors at Stanford have registered a smattering of signals, but an analysis suggests that these were caused by stray particles that originally came from cosmic rays and managed to bottom the 35 feet of rock over the detectors. The ever-so important question what is dark matter will not be answered tomorrow. More data has to be taken, the theories have to tweaked, and many physicists must continue to work together.