Question

Does conservation of moment hold in space expansion?

Answer 1

Expansion of universe especially due to the mysterious dark energy does mean that the energy is not conserved. In an isolated/closed system the law of conservation of energy still holds. ... Incidentally, the theory of general relativity does not need the energy to be conserved.

Answer 2

Everywhere in the universe expanding together. My question is, does conservation of momentum hold true in this ...

I would have to ask in return: "Conservation of momentum relative to what? What are we measuring