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Dark matter can refer to any substance which interacts predominantly via gravity with visible matter (e.g., stars and planets). Hence in principle it need not be composed of a new type of fundamental particle but could, at least in part, be made up of standard baryonic matter, such as protons or neutrons. Most of the ordinary matter familiar to ...
The density of dark matter in an expanding universe decreases more quickly than dark energy, and eventually the dark energy dominates. Specifically, when the volume of the universe doubles, the density of dark matter is halved, but the density of dark energy is nearly unchanged (it is exactly constant in the case of a cosmological constant).
The majority of ordinary matter in the universe is found in atomic nuclei, which are made of neutrons and protons. These nucleons are made up of smaller particles called quarks, and antimatter equivalents for each are predicted to exist by the Dirac equation in 1928. [8] Since then, each kind of antiquark has been experimentally verified.
Dark matter makes up most of the universe and decides how it grows – but still remains mostly mysterious. Skip to main content. 24/7 Help. For premium support please call: 800-290-4726 ...
Across the universe Zooming in on a portion of the Euclid telescope's map 600 times reveals the galaxies within the cluster Abell 3381, located 470 million light-years away from Earth. - ESA
The thinning of matter over time reduces the ability of gravity to decelerate the expansion of the universe; in contrast, dark energy (believed to be a constant scalar field throughout the visible universe) is a constant factor tending to accelerate the expansion of the universe.
A consequence of metric expansion being due to inertial motion is that a uniform local "explosion" of matter into a vacuum can be locally described by the FLRW geometry, the same geometry that describes the expansion of the universe as a whole and was also the basis for the simpler Milne universe, which ignores the effects of gravity.
This analysis shows that the Universe is flat to within 1 / 2 percent, and that it is homogeneous and isotropic to one part in 100,000. Inflation predicts that the structures visible in the Universe today formed through the gravitational collapse of perturbations that were formed as quantum mechanical fluctuations in the inflationary epoch.