Question: Multiple Universes?

[Kuroneko]

But shouldn't the dots expand, as are galaxies are expanding as well?

They don't, but one can imagine that cosmic expansion 'tries to' make them do so.

Because the force required to stay stationary near the horizon diverges to infinity, continuious objects of size greater that the distance to the horizon are impossible, as they would get ripped apart. That's an extreme case, but even smaller objects will get some tension put on them by the cosmic expansion.

However, remember that we're not dealing with a dust of noninteracting particles that could be dispersed easily, but with clusters of stars held together by gravity. In general, gravitationally bound systems will bound--galaxies, stars, planets, etc. will not expand.

Or, I should say getting more space in between them?

The quick answer to that would be "no, because their self-gravity or other forces pull them together." There is a speculative scenario where that does not happen--the so-called "Big Rip", where cosmic expansion accelerates so greately as to rip apart everything, but it's not part of the standard models, because it requires a peculiar form of dark energy for which there is no evidential support.


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In the standard Schwarzschild metric with a cosmological constant Λ that describes cosmic expansion (or contraction, as the case may be), the the radial acceleration of a stationary test particle is
d²r/dt² = -GM/r² + Λc²r/3
If Λ = 0, we get Newton's law of gravitatation. Note that one can interpret a positive Λ as if it was an outward force proportional to distance.

[Simon_Jester]

But shouldn't the dots expand, as are galaxies are expanding as well? Or, I should say getting more space in between them?

On the scale of galaxies, the gravitational and electromagnetic forces that hold atoms together into celestial bodies and celestial bodies into star systems and galaxies are much more powerful than the (for lack of a better term) "expansion force." Gravity pulls you and your neighbor back together faster than the inflation of the universe can push you apart.

Over extremely long, intergalactic distances, the rules change: the gravitational force between galaxies is mind-crushingly tiny, and the distances expansion has to play with are mind-crushingly huge. Since expansion is a percentage thing (all distances grow to be 100.000...0001% of what they were the day before, every day), the effect of expansion gets a lot more impressive as you look at cosmic distance scales, while being totally irrelevant at galactic or smaller scales.