- #1
johne1618
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If one considers a proper region of space then the (proper) density of mass/energy will change for two reasons.
1/ Matter is carried out of the region by the expansion of space.
2/ Energy changes as work is done on that matter by pressure.
But if one considers a co-moving region of space then there is no expansion and therefore there should be no change in co-moving density.
Is this correct?
1/ Matter is carried out of the region by the expansion of space.
2/ Energy changes as work is done on that matter by pressure.
But if one considers a co-moving region of space then there is no expansion and therefore there should be no change in co-moving density.
Is this correct?