Dark energy is manifested with its current energy density in every new unit of volume as the universe continues to expand, while the average dark matter and ordinary matter densities decrease inversely as the volume grows. Nowadays the existence of Dark Matter (DM), the dominant non-baryonic component of the matter density in the Universe, is well established. Dark Energy, Dark Matter In the early 1990s, one thing was fairly certain about the expansion of the universe. For example, it is quite possible that the halo of our. It is about the equivalent of 2.5 protons per cubic meter, on average throughout the universe. Sergio Pastor, in Les Houches, 2007. Galaxy is flattened into an ellipsoid, and there may be a component. WMAP and Dark Matter / Dark energy. To understand why, let’s see why normal matter does have density. It might have enough energy density to stop its expansion and recollapse, it might have so little energy density that it would never stop expanding, but gravity was certain to … The number of scattering events between a dark matter particle and a nucleus depends on the strength of their interaction, the scattering cross section, which is governed by the microphysical theory of dark matter. Dark matter doesn’t have a density. density of dark matter near the Sun. This implies that in the past, dark energy was less important, but it will dominate more and more as the universe continues to expand. The mass density at the current time was assessed by WMAP to be Ω m,0 = 0.27 +/- 0.04. of the halo velocity which is rotational and not isotropic. Dark matter makes up 30.1 percent of the matter-energy composition of the universe; the rest is dark energy (69.4 percent) and “ordinary” visible matter (0.5 percent). By making accurate measurements of the cosmic microwave background fluctuations, WMAP is able to measure the basic parameters of the Big Bang model including the density and composition of the universe. Dark Energy, Dark Matter In the early 1990s, one thing was fairly certain about the expansion of the universe. At the radius of Earth's orbit: $1.4 \times 10^{-19} \mathrm{g/cm^3}$ At the radius of Mars's orbit: $1.4 \times 10^{-20} \mathrm{g/cm^3}$ The density parameter is the ratio of the average density of matter and energy in the Universe to the critical density (the density at which the Universe would stop expanding only after an infinite time). 5.2 Neutrinos as dark matter. ... Gamma ray telescopes, like Fermi Gamma ray Space Telescope, are observing the Galactic center (where the highest density of nearby Dark Matter should exist) and are searching for specific Gamma ray energy signatures. But we do not know what the mass of individual dark matter particles is and thus the numeric density is unknown. Dark matter, a component of the universe whose presence is discerned from its gravitational attraction rather than its luminosity. If you put a bunch of iron atoms on Earth in close quarters, they will settle down into some object and stay still on the ground. The density of dark matter depends on the properties of the individual dark matter particles, just like the density of everyday materials depends on what they are made of.