Since it was found that the universe expands earlier than originally thought, astronomy & physical science have been flooded with activity. As a result of this finding, we may conclude that our basic ideas about how gravity works at cosmic distances are erroneous. An easy solution to the problem of general relativity is to add a constant to the field equations. For this reason, and others, scientists have looked into several possible explanations for the anomalously low value of the cosmological constant. These include, among other things, the advent of a novel negative-pressure fluid or changes to general relativity. Evidence for cosmic acceleration will be examined in this section. Here are some of the theories that have been proposed to explain this phenomenon, including the cosmological constant and its variations, quantum mechanic variations of essence, mass-variable neutrinos, and general relativity modifications. Methods for testing some of the theories presented in this Paper will be examined in this chapter's concluding section.
Astronomical, Universe, Quantum mechanic, Cosmology, Dark energy, Theory, Gravitational theory
