3 ms·
> To be specific it's the "average time across all space" ran more slowly, No, that is not what happened. The article's description is seriously misleading. Th
by pdonis 3y ago
> To be specific it's the "average time across all space" ran more slowly,
No, that is not what happened. The article's description is seriously misleading. The effect it is describing is only an appearance due to the redshift. it does not mean time "actually ran slower" back then.
> here's no "low density" patch so you're actually comparing it to something that doesn't exist quite yet, hence a bit weird?
Not just "a bit weird"--wrong. What you are saying here is a crucial difference between the universe as a whle and an isolated gravitating mass like a black hole, and that difference means that the notion of "gravitational time dilation" that works for an isolated gravitating mass is not valid for the universe as a whole. The "time dilation" described in the article is not like the gravitational time dilation around a massive object. It is like the "time dilation" due to relative motion in special relativity, which is only apparent and does not reflect any actual difference in clock rates.
- jeremyjh 3y agoWhy would there not be gravitational time dilation in a denser early universe as the article describes?
- pdonis 3y agoThe reason the GP gives is a step in the right direction: the density is constant everywhere in space at a given point in time, and variations in "gravitational potential" (which are necessary for gravitational time dilation) can only be present if there are differences in density. A more technically correct reason is that the concept of "gravitational potential" (and hence gravitational time dilation) is not even well-defined in an expanding universe. "Gravitational potential" is only well-defined in a stationary spacetime, which means one in which the geometry does not change with time. An expanding universe is not a stationary spacetime. (But even in a stationary spacetime, variations in gravitational potential, which require variations in density, are necessary for gravitational time dilation to exist. That is why the GP's answer described above is a step in the right direction.)