I have a question.

[Tank]

Just because the universe expands does not mean gravity will be "diluted". Gravity depends on the amount of mass of an object(s) and the amount of mass will constitute for the strength of gravity, not the space around it.

The effect of gravity is expressed as square law, doubling the distance reduces the effect by a factor of four. As the universe is expanding the galaxies are moving apart this will dilute the effect of gravity as the existing mass is expressing gravity within a greater volume.

Do you mean from each other? Or the galaxy itself is "unwinding"?

In general the galaxies are moving apart from each other due to the volumetric expansion of the universe. Any one galaxy my be growing or shrinking within itself based on the matter within it. Any pair or group of Galaxies may be gravitationally bound together and they could be moving in any relative direction to each other.

EDIT

Here are two galaxies doing a gravitational tango



These two have been merging for a long time.



More images at the Hubble site here http://hubblesite.org/gallery/album/galaxy

[hackenslash]

Indeed. Galaxies are gravitationally bound, so are not subject to cosmic expansion.

Does this not imply that gravity is an aberration and that expansion is the norm? Thus as the universe expands, and the effects of gravity are diluted, that accelerating expansion would be expected to occur?

See my post on dark matter/energy for this. In the absence of a driving force behind expansion, it would be expected to slow under gravity or remain constant as the effects of gravity are reduced by distance. The fact that expansion is actually accelerating tells us something must be going on, because that requires repulsion in some form, which is what dark energy is.

[DropLogic]

Indeed. Galaxies are gravitationally bound, so are not subject to cosmic expansion.

Does this not imply that gravity is an aberration and that expansion is the norm? Thus as the universe expands, and the effects of gravity are diluted, that accelerating expansion would be expected to occur?

See my post on dark matter/energy for this. In the absence of a driving force behind expansion, it would be expected to slow under gravity or remain constant as the effects of gravity are reduced by distance. The fact that expansion is actually accelerating tells us something must be going on, because that requires repulsion in some form, which is what dark energy is.

So...for a short time after the big bang, space expanded faster than c, but it slowed down?  But is still accelerating?  When did dark matter come into play? Is space still expanding faster than c?

[hackenslash]

Yes, the universe is expanding at greater than c, because the expansion is not subject to that limitation. It isn't actually travelling, in the same way that the galaxies receding from us aren't travelling. The recession is a result of the expansion of space, and no actual travel is occuring.

Dark matter has always been in play. It's useful to know what dark matter actually is, which you can find in my post about gravity.

As for the bit about the early expansion of the cosmos, it is necessary to deal with what is known as the 'inflaton' field, which would require quite a long essay. This is actually one of the things that Brian Greene deals with really well in Fabric of the Cosmos, so worth a read just for that.