- #36
CJames
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GrayGhost said:Would it not be proper to say that space contracts in a gravity well only if you progress to deeper potential, not if you remain at one gravitational potential?
What I'm getting at is that two objects which start out at rest with respect to one another will move toward one another. In that sense, the space between them is contracting. Universal expansion is just the opposite of this.
I do realize what you are saying. Yet, gravitation and spacetime expansion are 2 different things arising from 2 different sources. One is the suspected dark energy and the other is spacetime curviture from mass. How do we know that both activities do not occur in superposition within gravity wells? It seems reasonable that gravitation could overwhelm expansion within some reach, that spacetime expansion might be a negligable effect even though it exists in the well. EDIT: But then, as mentioned, there would likely be no way to prove it.
GrayGhost
While they come from two different sources, I wouldn't agree that they are two different things. They are both the effect of energy on spacetime. Mass causes geodesics to move toward each other, while negative pressure causes geodesics to move away from each other.
If you are saying that the negative pressure which causes space to expand is located at every point in space, I believe that this is the mainstream position. But this doesn't translate into saying that every point in space is expanding, because gravity overcomes this negative pressure several billion times over. It is only when this negative pressure wins out over gravity that space starts expanding.