There are two aspects to the properties of matter that contribute to the gravitational attraction; one is mass density and the other is "pressure". This results from Stress-Energy tensor component in Einstein's Field Equations. The concept, in this case, is that dark energy has a negative pressure so that as the universe expands the pressure gets greater (making it expand more).

What you're saying here, if I get you right, is that you can imagine space as something in where we have a lot of invisible boxes containing a negative pressure, restricting and constraining those boxes in a inverse direction, and as space around them grows bigger due to the 'expansion' the inverse pressure automatically become larger? The problem here is that you will need a 'box' it seems to me, to explain how this can happen?

As I'm not really sure how you otherwise expect that 'negative pressure' to become 'larger'?

And just how does it help an expansion?

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Or are you using 'negative' as a 'positive expanding force' here?

And then dark matter would be something 'welling forward' somehow, expanding space at the same time as holding it at a constant rate of approximately 74 percent to explain the apparent mass in our universe.

Doesn't make sense, why would our universe be closed, flat (Analysis of data from WMAP implies that the universe is spatially flat with only a 2% margin of error), and constantly balanced at the same apparent mass-mix, when it also is seen as expanding. If this is happening and our universe are 'growing' and our mass-mix is a constant? Then our universe as a whole will mass more if we trust in the idea of distance. And if we don't trust in that idea, we shouldn't speak of 'expansion' at all as it has to be something different, well, as I see it?

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Awhh, I had enough problems trying to understand a photon.

Will I have to understand this too?

Where will it end???

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And how can it be closed if it is growing (expanding) yet keeping a constant percentage of mass, mixed as matter, dark energy, energy, dark mass, and 'vacuum energy'? It doesn't matter if it its percentage is getting 'thinned out' or 'staying the same' or 'begetting more'. Either one of them should indicate a non closed universe it seems to me?

So what am I missing here?