Recent observations of the accelerating expansion of the universe have been quantified and for the time being given a name as to the cause: Dark Energy. And from what I've read from other, similar questions is that Dark Matter is a pressure that is causing this expansion, although we don't know the details of the mechanism yet behind this pressure.

But is there anything in our present theories of physics or observations that rules out gravity itself as the cause of this expansion? I'm thinking along the lines of an analogy: the nature of the strong nuclear force which, at close distance, tends to bind together nucleons, but at even closer distances repels them.

Couldn't this repulsive force we observe, this dark energy, just be the effects of the gravitational force on a larger scale of space?

  • $\begingroup$ I'm pretty certain the quesion I've linked is a duplicate, and the answers to it give the information you need. But if you disagree ping me here and I'll withdraw my close vote. $\endgroup$ – John Rennie Sep 22 '16 at 15:12
  • $\begingroup$ @JohnRennie Hi John, the OP mentioned Dark Energy in his question, but it really wasn't addressed by any of the answers. I've also read Moffat's book on modified gravity theory but don't recall him directly discussing anything ruling out the idea; his goal is to explain dark energy by modifying GR. Don't think he's there yet. My question -specific. What rules out the connection, if anything? $\endgroup$ – docscience Sep 22 '16 at 15:30
  • $\begingroup$ OK I'll withdraw the close vote $\endgroup$ – John Rennie Sep 22 '16 at 15:32
  • $\begingroup$ Related: Are modified theories of gravity credible? $\endgroup$ – John Rennie Sep 22 '16 at 15:33
  • $\begingroup$ @JohnRennie thanks, and thanks for the reference. Yes, looks like others besides Moffat considering modified theories of gravity to fit observations $\endgroup$ – docscience Sep 22 '16 at 19:51

From my understanding the strong force becomes "repulsive" due to the Pauli Principle. The areas of repulsion are just where the principle happens to overrule the strong force. I don't believe the sign of the force itself changes.

That being said, and someone could correct me if i'm wrong, i don't think the effects of the principle are enough to cause the expansion let alone the acceleration of the expansion of the universe.

  • $\begingroup$ It's not just the Pauli principal that is responsible for short range nucleon repulsion. The nuclear SRR causes the saturation of Nuclear forces. Electrons also obey Pauli principal, but become more and more densely packed in large atoms. $\endgroup$ – Lewis Miller Sep 25 '16 at 1:01

In a sense, yes.

Around the time of Newton, a contemporary of his, Fatio de Duillard, wrote about the effects of abberation of gravity or in simpler terms, what would happen if gravity traveled at a finite speed. This idea was studied by le Sage and later LaPlace who was trying to prove the stability of orbits so he had to address this theory which would predict some kind of "extra" force that would, well, expand things like galaxies and really anything that orbits (think accelerated expansion of the universe). Since we "knew" at the time (any time up until 1998) that the universe's expansion was not accelerating, and that orbits were stable, we also "knew" that gravity must travel infinitely fast. By the way that "proof" is still on Wikipedia.

Now that we know about the expansion of the universe, upon re-examining this discredited "shadow theory", this extra force which was once called impossible should be considered to be dark energy created by the lag in gravity between orbiting objects. After all, if gravity travelled at about 400 kps, or about 1/765 the speed of light, dark energy is created in the amounts seen by nasa or about %68 of the total gravity. There is a geometric proof of this in the paper Gravitas, Part One.


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