Dark Matter is a brief continuation of the neutrino story. CSUDH students were involved in the important discovery in Japan that neutrinos have mass. Although very small, they do have weight. Prof. Ganezer, of our Physics Department, suggested to us that the discovery of neutrino mass might lead to an understanding of dark matter.

Now, on Thursday, November 25, 1999, the Los Angeles Times, announced a new experiment: "The Energy of Emptiness," p. B2. Scientists have found that the parts of the universe we refer to as dark matter, because they give off no light, do have energy, which shows itself in the force with which metal plates are pushed together. Read the story on the LA Times' Website by searching for: "Hoping to Explain Everything,." Dark Matter

Dark matter has important consequences for the evolution of the Universe. According to standard cosmological theory, the Universe must conform to one of three 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 Omega) 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 back upon itself. For the case where Omega is exactly equal to one, the Universe is delicately balanced between the two states, and is said to be "flat". In the figure above we show graphically some of the measurements of the density of the universe which we have discussed above. what is plotted is the density of the universe, both visible matter and the inferred "dark matter", as a function of the "scale" at which the measurement was made, from the local neighbourhood up to the largest scales. on the smallest scales, probed by oort, the visible matter and three times as much dark matter give omega about 1/1000. as we go to larger and larger scales the inferred value of omega increases, although the measurements become harder and progressively more uncertain. the next point to the right is the mass in galaxies, which moves to the position of the higher dot if we include the dark matter inferred from rotation curves. then on larger scales we have the measurements from the motions of clusters of galaxies and the cosmic microwave background. the yellow band indicates the amount of matter that can reside in "normal" matter, or baryons, as inferred from nucleosynthesis. if there is more matter in the universe than this, as the measurements appear to be telling us, then it must be made up of some strange particle which is not familiar to us here on earth.