Why the Universe is on expansion? The Universe should be on CONTRACTION if. Newton's law of Universal Gravitation would be the reality. So, there is no REAL and scientific explanation for present state of EXPANSION. The vague explanations are there based on "Big-Bang Explosion", "Inertial Force" and "Space-Time-Curvature" being considered for expansion of the Universe. But all these factors are fictitious and non-existing. Therefore, there is no scientific explanation for this violent phenomenon of the Universe. The real explanation is there in STREPULSION-PHYSICS (SRP), the new branch of Science which is established by the Authors. According to SRP, STARS EXERT REPULSION FORCE. Owing to mutual Repulsion between Stars, GALAXIES are EXPANDING. As most of the mass of Galaxies is condensed into Stars, Galaxies exert Repulsion Force. Owing to mutual Repulsion force between Galaxies, GALACTIC CLUSTERS are EXPANDING. Galactic clusters exert force of Repulsion. Owing to mutual Repulsion force between Galactic clusters, the UNIVERSE is EXPANDING. This is the mystery of EXPANDING UNIVERSE. This expansion is followed with DISPERSION of Stellar mass and CONVERSION into Radiating energy and Repulsion force. Therefore, there will be no REVERSE COURSE of CONTRACTION. Expansion will continue till entire physical mass of Stellar Universe is converted in the form of energy and force. As ratio of Stellar Repulsion force is goes on increasing with time, ratio of expansion of the Universe is also goes on increasing with time. So, present Universe is on expansion in higher ratio than five billion years ago.
This expansion of the universe, with nearby galaxies moving away more slowly than distant galaxies, is what one expects for a uniformly expanding cosmos with dark energy (an invisible force that causes the universe's expansion to accelerate ) and dark matter (an unknown and invisible form of matter that is five times more common than normal matter). This is what one would also observe of blueberries in an expanding muffin. Dark energy is the name given to the mysterious force that is accelerating the rate at which our universe is expanding. Astrophysicists are busily engaged in investigating the nature of dark energy. These are difficult studies, but they are worthwhile, because dark energy will determine the ultimate fate of our universe. Our current state of knowledge of dark energy is summarised by Adam Riess and Mario Livio in Scientific American (March 2016).
We have known that our universe is expanding – that is, galaxies and clusters of galaxies are moving away from each other – since the observations of Edwin Hubble in the 1920s. It was thought that the rate of expansion would slow down over time as gravity gradually exerted a braking effect. However, about 20 years ago it was surprisingly discovered that not only is expansion not slowing down, it is actually speeding up. Some repulsive force is pulling the universe apart and this force was dubbed “dark energy”.
Riess and Livio describe the three main hypotheses to explain the nature of dark energy. The leading hypothesis is that dark energy is a property of empty space itself and this hypothesis fits the astrophysical evidence better than the other two. A second hypothesis is that the universe is permeated by an energy field called quintessence that counteracts the attractive pull of gravity. The third hypothesis is that there is no such thing as dark energy and that the accelerating expansion of the universe is caused by currently unknown properties of gravity that only manifest themselves over vast scales such as (https://www.irishtimes.com/news/science/dark-energy-the-repulsive-force-that-is-pulling-the-universe-apart-1.2736328over the entire observable universe.)
News from today's astronomers.
1)Data discrepancies may affect understanding of the universe
One of the unsolved mysteries in modern science is why the expansion of the universe appears to be accelerating. Some scientists argue it is due to a theoretical dark energy that counteracts the pull of gravity, while others think Albert Einstein's long-accepted theory of gravity itself may need to be modified.
As astrophysicists look for answers in the mountains of data gathered from astronomical observations, they are finding that inconsistencies in that data might ultimately lead to the truth.
"This is like a detective story, where inconsistent evidence or testimony could lead to solving the puzzle," said Dr. Mustapha Ishak-Boushaki, professor of astrophysics in the School of Natural Sciences and Mathematics at The University of Texas at Dallas.
Phys.org