DARK MATTER:
Dark matter hypothesis, we can try to justify using newtons universal law of gravity: There is a stronger gravitational field at larger distances. Also, additional unseen mass is provided to understand the hypothesis. Both Milgrom’s modified Newtonian dynamics (MOND) theory and Robson’s recent quantum theory of gravity provided by the generation model (GM) of particle physics is used to understand dark matter hypothesis.
Phenomenon:
The notion of “dark matter” emerged from several astronomical observations concerning the structure of galaxies, the rotation of stars and neutral hydrogen gas in spiral galaxies, the motions of clusters of galaxies, and so on. The cosmological discontinuity with Newtons Universal Law of Gravity described as dark matter.
Here cluster contained considerably more “dark matter” than the visible galactic matter in order to account for the fast motions of the galaxies within the cluster and also to hold the cluster together.
One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not nothing. Space has amazing properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space to come into existence.
One version of Einstein's gravity theory is that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands. As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the universe to expand faster and faster.
First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the universe to make up the 27% required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates with matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough lensing events to suggest that such objects to make up the required 25% dark matter contribution.
Standard model of cosmology assumes that the universe is now composed of about 5% ordinary matter, 27% dark matter, and 68% dark energy, so that dark matter constitutes about 84% of the total mass, while dark energy plus dark matter constitute about 95% of the total mass-energy content of the universe.
The existence of dark matter in the universe suggests that one requires new physics beyond the SM. Three such particles have been searched for without success:
(1) axions
(2) weakly interacting massive particles (WIMPS), and
(3) sterile neutrinos.
These three particles are all hypothetical particles
Expansion of the Universe:
Unlike normal matter, dark matter does not interact with the electromagnetic force. This means it does not absorb, reflect or emit light, making it extremely hard to spot. In fact, researchers have been able to infer the existence of dark matter only from the gravitational effect it seems to have on visible matter.
The distribution of dark matter, galaxies, and hot gas in the core of the merging galaxy cluster Abell 520. The result could present a challenge to basic theories of dark matter. It might have so little energy density that it would never stop expanding, but gravity was certain to slow the expansion as time ticking on. the expansion of the universe has not been slowing due to gravity, as everyone thought, it has been accelerating. The universe is full of matter and the attractive force of gravity pulls all matter together. Roughly 68% of the universe is dark energy. Dark matter makes up about 27%. The rest - everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the universe.
Neutrinos:
Neutrinos could be key particles to unravel the nature of the DM in the Universe. It is clear, though, that massive neutrinos and dark matter are both part of nature and should be incorporated in models of physics beyond the standard model. It may be that they are related to each other and that, in addition, both originate from new physics at the TeV scale.
Astrophysical and cosmological evidence implies that neutrinos have masses, neutrinos provide only a small cosmic dark matter component. The study of solar neutrinos provides important information on nuclear processes inside the Sun as well as on matter densities. Moreover, supernova neutrinos provide sensitive probes for studying supernova explosions, neutrino properties and stellar collapse mechanisms. Neutrino-nucleus reactions at energies below 100 MeV play essential roles in core-collapse supernovae, explosive and r-process nucleosynthesis.
With this we also consider Milgrom MOND theory, Robson quantum theory of gravity to emphasize the dark matter hypothesis. The possible mass discrepancy within a galaxy led to the dark matter hypothesis whereby each spiral galaxy is embedded within a huge spherical halo of dark matter. The only alternative to dark matter was considered to be an appropriate modification of Newtonian gravity to provide the required extra gravitational field at large (galactic) distances.
One theory suggests the existence of a “Hidden Valley”, a parallel world made of dark matter having very little in common with matter we know.
