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I'm not a physics guy, but this is something I have always wondered about. If a clock flown by an object of high mass runs slower, what is the effect of this in regards to the density of the universe. It seems to me that as the universe expands, it would lose density and therefore clocks would run faster as the universe expands. Is this correct? And if so, could this create the perception of an accelerating expansion in a hypothetical universe of constant expansion. I want to understand the things I believe in, and I believe in the big bang. It seems that if the universe were a singularity at some point that a nearby clock would be running infinitely slow. Would the first few seconds of the big bang be perceived as slow, maybe from a distant view, despite much happening in the first few seconds? (I'm not sure how the human brain perceives time). Forgive my complete lack of understanding. I'm just curious if and how this is accounted for in the models.

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marked as duplicate by John Rennie, Neuneck, Kyle Kanos, ACuriousMind, Ali Sep 2 '14 at 13:54

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  • $\begingroup$ The "singularity" is a very poor picture for the initial state of the universe (if there even was such a state, but let's not get too technical). The physical laws that we know now would not have allowed an infinitely small, infinitely dense universe, not even in the beginning. Even under the most extreme circumstances, the universe could not have been smaller than a Planck length, because one could not measure anything smaller than that scale. It is much more likely, though, that the universe was never that small., we just don't know how small it was, at its smallest. $\endgroup$ – CuriousOne Sep 2 '14 at 3:09
  • $\begingroup$ Thanks for clearing that up. It seems reasonable that universe would not have infinite density or infinitely small size. Singularity does seem like a poor choice or words. Maybe I should edit my post... $\endgroup$ – user14241 Sep 2 '14 at 3:19
  • $\begingroup$ I think the use of singularity in physics is easily misunderstood. What is actually meant by "singularity", is that the known theories break down at a certain scale or for a certain choice of parameters and that a better theory is needed to explain what really happens on that scale. The physics community needs to do a better job explaining this, and maybe it's time to find a better terminology. $\endgroup$ – CuriousOne Sep 2 '14 at 7:02
  • $\begingroup$ Thanks guys. The link does help me understand things better. Sorry about the possible duplicate. I'm gonna take some time to wrap my head around both discussions, and hopefully things will become more apparent. $\endgroup$ – user14241 Sep 2 '14 at 13:52
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It seems to me that as the universe expands, it would lose density and therefore clocks would run faster as the universe expands. Is this correct?

No. At a conceptual level, you can't define "faster" if you don't have something else to compare with. In technical terms, gravitational time dilation is only defined in a static spacetime, and cosmological spacetimes aren't static.

Would the first few seconds of the big bang be perceived as slow, maybe from a distant view, despite much happening in the first few seconds? (I'm not sure how the human brain perceives time).

The big bang was not an explosion that took place at one point, surrounded by empty space. It happened everywhere at once.

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  • $\begingroup$ Thanks for the comments. I do see the problem in having no point of reference, but I still can't understand why a universe of extreme density would have a clock run as fast as the same universe in a state of lower density, given the effect of gravity on time and space. I'm not doubting your explanation. I just don't have adequate knowledge of relativity and other theories to understand your explanation. $\endgroup$ – user14241 Sep 2 '14 at 3:35

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