Gravitational instabilities give rise to conglomeration of matter in the form of various structures. Non-baryonic Hot Dark Matter (HDM) particles are conjectured to have decoupled from rest of the matter/radiation when their speed was relativistic. Cold Dark Matter (CDM) particles are, however, conjectured to have small velocity dispersion and are assumed to have decoupled from matter/radiation when their speed was non-relativistic. CDM simulations fit well with the evolution of large-scale structure of universe and disagree with observations on small scale distances. A general assumption is that dark matter in galaxies and clusters is subject only to Newtonian gravity.
We call the dark matter of our universe ‘dark’ because it (almost) neither emits nor absorbs
electromagnetic radiation. Historically, the observational evidence for the existence of
dark matter came only from galactic dynamics and is gravitational. The presence of dark
matter can be inferred from gravitational effects on visible matter. According to the present
observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter
accounts for the vast majority of mass in the observable universe.
Newtonian gravity applied to galaxies and galaxy clusters leads to much higher mass
estimates than expected from the observed stars and galaxy cluster. This discrepancy is
mostly interpreted as evidence of dark matter. However, it could also indicate a breakdown
of Newton’s law in regime of large-scale and low acceleration. Dark matter and modified
gravity are the only two logical explanations for the data. It is proved that the entire
universe is made up of 74% dark energy, 24% dark matter and 4% visible matter. Dark
energy could be the energy of a huge number of gravitons. Photons traveling from one galaxy to another could emit gravitons that add to the dark energy total and keep the
density of dark energy constant. Also, if the gravitons carry the color force like gluons,
then they would be inhibited by other gravitons. When they travel from one mass to
another they would lose energy to other gravitons and the force of gravity would be very
weak by the time they reached a distant mass.
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