quote:
Well, I would assume that a universe of infinite size would contain infinite mass. Therefore I don't see how a universe of infinite mass could expand at all - it should immedately collapse. Could it even expand?
I'm no expert in this, but I believe if the mass density of the universe had been too small, then it would be
open, meaning, essentially, that it would extend forever in all directions.
And would expand forever.
Paradoxically, it is when the mass density is great enough that the universe will eventually collapse - but that implies a
closed universe, one that has finite total volume.
As it is, the latest I've heard is that the universe may very well be perflectly
flat (over large scales), meaning that it does extend forever. Also, the latest observations seem to indicate that there is a repulsive force (akin to Einstein's cosmological constant) that is described in the term "dark energy".
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