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General Discussion
Why the universe expansion is accelerating.

Gravity exists because matter takes up space bounding things to planets and stars. There is either an infinite amount or a growing amount of space beyond the known universe (a cluster of galaxies). This fabric of space is weight and it started carrying matter outward. As it is carying matter outward it is starting to accelerate as it started expanding.

QUOTE: Gravity exists because matter takes up space bounding things to planets and stars.

The first you have to understand that Einstein's theory of General Relativity is a continuation or extension of Newton's law of gravity. General relativity is a theory of the behavior of space and time In General Relativity, spacetime becomes curved in response to the effects of matter. In General Relativity, a massive body like the sun causes the spacetime around it to curve, and this curvature in turn affects the motion of the planets, causing them to orbit around the sun. In short, General Relativity is a theory in which gravity is described by saying that space and time are dynamics quantities that can curve in response to the effects of matter and can in turn alter the behavior of matter. The laws of physics that were known prior to General Relativity, most notably Newtonian physics and special relativity, were only valid in a restricted set of coordinate systems known as inertial reference frames. The laws of General Relativity are formulated in a way that is equally valid in any reference frame.

QUOTE: There is either an infinite amount or a growing amount of space beyond the known universe (a cluster of galaxies). This fabric of space is weight and it started carrying matter outward. As it is carying matter outward it is starting to accelerate as it started expanding.

Einstein initially thought that the universe was static: that it neither expanded nor shrank. When his own Theory of General Relativity clearly showed that the universe should expand or contract, Einstein chose to introduce a new ingredient into his theory. His "cosmological constant" represented a mass density of empty space that drove the universe to expand at an ever-increasing rate. When in 1929 Edwin Hubble proved that the universe is in fact expanding, Einstein repudiated his cosmological constant.

In 1998, observations of very distant supernovae demonstrated that the universe is expanding at an accelerating rate. This accelerating expansion seemed to be explicable only by the presence of a new component of the universe, a "dark energy," representing some 70 percent of the total mass of the universe. Of the rest, about 25 percent appears to be in the form of another mysterious component, dark matter; while only about 5 percent comprises ordinary matter, those quarks, protons, neutrons and electrons that we and the galaxies are made of. The problem with dark energy solution: If dark energy were the size that theories predict, the universe would have expanded with such a fantastic velocity that it would have prevented the existence of everything we know in our cosmos. We may soon be able to distinguish between a new solution and the dark energy solution. New data will soon give us an explanation for the accelerated expansion of the universe.

An original solution to this puzzle was put forward by four theoretical physicists, Edward W. Kolb of the U.S. Department of Energy's Fermi National Accelerator Laboratory, Chicago (USA): Sabino Matarrese of the University of Padova; Alessio Notari from the University of Montreal (Canada); and Antonio Riotto of INFN (Istituto Nazionale di Fisica Nucleare) of Padova (Italy).

New solution: The present acceleration of the universe is a consequence of the standard cosmological model for the early universe: inflation. The new solution to the paradox posed by the accelerating universe relies on the so-called inflationary theory, born in 1981. According to this theory, within a tiny fraction of a second after the Big Bang, the universe experienced an incredibly rapid expansion. This explains why our universe seems to be very homogeneous. Recently, the Boomerang and WMAP experiments, which measured the small fluctuations in the background radiation originating with the Big Bang, confirmed inflationary theory. It is widely believed that during the inflationary expansion early in the history of the universe, very tiny ripples in spacetime were generated, as predicted by Einstein's theory of General Relativity. These ripples were stretched by the expansion of the universe and extend today far beyond our cosmic horizon that is over a region much bigger than the observable universe, a distance of about 15 billion light years. It is the evolution of these cosmic ripples that increase the observed expansion of the universe and accounts for its acceleration. Adding this new key ingredient, the ripples of spacetime generated during the epoch of inflation, to Einstein's General Relativity to explain why the universe is accelerating today. It seems that the solution to the puzzle of acceleration involves the universe beyond our cosmic horizon. No mysterious dark energy is required.

"Whether Einstein was right when he first introduced the cosmological constant, or whether he was right when he later refuted the idea will soon be tested by a new round of precision cosmological observations," Kolb said. "New data will soon allow us to distinguish between our explanation for the accelerated expansion of the universe and the dark energy solution."

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