Hi, layman here, but hopefully reasonably educated. I did not know whether this question might fit better under relativity or under cosmology so I'm posting it here. General Relativity tells us that time slows down in gravity wells. The cosmic expansion tells us that the energy density in space has been getting smaller and smaller since the very early epochs of the universe. Even if the dark energy remains constant, the matter (baryonic + dark) density is certainly getting smaller, so the overal energy density in space must be getting smaller. Consequently it seems logical to believe that the rate of time elapsing has been getting faster and faster as space expands. When the universe was very young and small it's energy density was very high some time must have run rather slowly. Conversely, in the current universe the average energy density is much lower so time must be running faster. I am aware that if these are universal statements, they may have no physical meaning. When talking about the rate of time elapsing in the universe, we have no external clock to compare to, so such a rate of time elapsing will always look the same to anything inside that universe. We may have the above theoretical reasons to believe that early in the universe time must have been ticking slower, and that now time must be ticking faster, but if there is no external clock to compare those to, they probably become meaningless. What can you say about this reasoning? Am I completely wrong in something? or partly right? Was time really running slower in the early universe than now, and if so does that have any significance, now or perhaps looking to a remote future when the rate of expansion will be much faster than now? Thanks!