Is Gravity in the vaccum of space decelerating or exspanding? please explain why,when and how in detail, Along with a credible reference. If Science has not concluded either please give a reference as well.

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    $\begingroup$ What do you mean by "the opposing force to gravity"? $\endgroup$ – HDE 226868 Feb 20 '16 at 16:13
  • $\begingroup$ I think this question is referring to Newton's third law, "for every action there is an equal and opposite reaction." $\endgroup$ – David Baucum Feb 20 '16 at 16:37
  • $\begingroup$ Gravity is not a force; hence, there isn't a true "opposing force". Maybe you are referring to dark energy? $\endgroup$ – Sir Cumference Feb 20 '16 at 20:05
  • $\begingroup$ Well yes darkenergy was my first assumption only if the gravity were on the edges of the universe, it should not meet any other force or particles. $\endgroup$ – user5434678 Feb 20 '16 at 23:24
  • $\begingroup$ Would the strength of the spin in a galaxy deplet a neighboring galaxies gravity when the two gravitational forces meet? $\endgroup$ – user5434678 Feb 20 '16 at 23:26

The only known theoretical way to stop gravity is "antigravity", as needed to stabilize a wormhole. For this you need negative energy, which has been observed only on small scales and in small amounts. For any practically relevant scenarios gravity sums up. Observational evidence for "antigravity" is negligible compared to usual gravity.

But in some sense the accelerating universe due to dark energy limits the range of the gravity of a mass, since gravity propagates with the speed of light. For particles outside the cosmological event horizon of the considered mass, the field of gravity of the considered mass will never reach those particles.


Newton's third law is that if a body A exerts a force on body B, then body B exerts an equal (in magnitude) and opposite (in direction) force on body A. In Newtonian gravity when body A exerts a gravitational force on body B, then body B exerts an equal gravitational force on body A. As both forces are attractive they have opposite directions.

General relativity doesn't treat gravity as a force, but Newton's third law can be demonstrated in the Newtonian limit of GR.

In big bang cosmology the initial expansion is not due to gravity or any other "force", rather it comes from the initial conditions of the Universe. Matter and radiation have positive energy density and non-negative pressure which both contribute to their gravity which acts to slow down the rate of expansion (the Hubble parameter). However it has been demonstrated that the Universe's rate of expansion is in fact increasing which means that there must exist some form of dark energy which has a negative pressure which is large enough in proportion to its (positive) energy density to accelerate the expansion of the Universe.

  • $\begingroup$ There are weak,strong,EM radiation and gravity.These should be stated as the present known forces in a vaccum.If gravity is not a force it would have to be considered a medium and a particle.Right or wrong.Or is this challenged because gravity is only a force in a vacuum and nowhere eles? $\endgroup$ – user5434678 Feb 21 '16 at 6:12
  • $\begingroup$ @Gerald- Antigravity Can not take place in a vacuum correct? And if gravity is not losing the original kinetic energy from the big bang then I would agree that the Infamous Elusive Dark energy would have to be the opposing force that could stop gravity from a infinite expansion.So are you saying gravity is constant in a vacuum as of now? $\endgroup$ – user5434678 Feb 21 '16 at 6:55
  • $\begingroup$ Strictly speaking, negative energy isn't exactly vacuum, but less than that, since not all vaccum quantum fluctuations are allowed. For kinetic energy you need a system of reference. $\endgroup$ – Gerald Feb 21 '16 at 10:09

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