I mean to add . . .
Edmund Storms writes:
"How does a star at one side of a galaxy know that its gravity and momentum are being exactly balanced by a star on the other side when this information takes a million years to pass between the two stars."
Do we know that it balances exactly? Perhaps close examination would reveal that the balance propagates at the speed of light. I suppose it might be difficult to tell the difference in many cases. Perhaps you could see it in effects from other, nearby or impinging galaxies.
- Jed
