It is my understanding from reading a few threads that remote clusters don't have any "speed" relative to us, they are simply moving away. Does this mean they have no momentum? And if that is true, does that imply that they have no mass (in this context, not in a local context). And if that is true wouldn't that imply that distant galactic clusters can be accelerated without requiring any force? Would that imply that the dark energy causing an acceleration of expansion is really not so much energy as it is simply something that pushes a massless cluster to accelerate? Just some fun Sunday morning musings. Comments welcome.