Was the flow of time slower in the early universe?

[jalak7]

When the universe was young, and everything was closer together, did the extra gravity cause time to run slower than it does now?

 

[Mordred]

This question is better suited in the relativity forum. Your going to need to define from which observer? Time dilation is relative to the observer. This link is from our observer perspective.

http://www.newscientist.com/article/dn13792-cosmic-time-warp-revealed-in-slowmotion-supernovae.html

here is another link that has several links to observed time dilation

http://www.astro.ucla.edu/~wright/cosmology_faq.html#TD

When you see the history of the universe plotted against time, the time used is the comoving time i.e. the time measured by a clock that is at rest with respect to the universe around it. This is the time co-ordinate used in the FLRW metric, which is a solution to the equations of GR that, as far as we can tell, gives a good description of the universe back to very early times.

 

[Crazymechanic]

Quite logically from what we know the simple answer would be yes.And considering that the early universe was much more dense , in fact a lot more dense I would say that time run slower for every average observer no matter where one would be in the early universe.
As it expanded it became more and more like the universe we know today with planets and black holes with huge mass and hence gravity around them and then with a lot of "empty" space between with quite small gravitational potential.

 

[Chronos]

If all clocks run more slowly what effect would that have? It would be undetectable. Gravitational redshift is vanishingly small unless you are very near a compact object. The universe is not a compact object.

 

[timmdeeg]

Quite logically from what we know the simple answer would be yes.And considering that the early universe was much more dense , in fact a lot more dense I would say that time run slower for every average observer no matter where one would be in the early universe.

It seems you are talking about 'proper' time, the time your wristwatch is showing. By no means can you tell that the time it shows runs slower.
In contrast, if you watch a Galaxy in the early universe, then its redshift is due to cosmic time dilatation caused by the expansion of the universe. But then we talk about coordinate time.

 

[Mordred]

Quite logically from what we know the simple answer would be yes.And considering that the early universe was much more dense , in fact a lot more dense I would say that time run slower for every average observer no matter where one would be in the early universe.
As it expanded it became more and more like the universe we know today with planets and black holes with huge mass and hence gravity around them and then with a lot of "empty" space between with quite small gravitational potential.

The only era in the past that might (key word might) be dense enough to dilate time would be prior to the inflationary era. We would never be able to see this far back. Due to the shroud of
darkness. Here is one of the furthest objects we can see and why.

http://www.newscientist.com/mobile/article/dn22611-hubble-sees-earliest-known-galaxies-through-cosmic-fog.html

 

[Chalnoth]

The only era in the past that might (key word might) be dense enough to dilate time would be prior to the inflationary era.

I'm not sure there's actually any time dilation at all from the average matter density.

 

[Mordred]

To be honest with you neither am I. Granted I also cannot find any reliable source with an estimate of the density of the Planch and GUT epoch. Some of the older particle physics articles covering the TOE aspects of these epochs. Place the density around 10^78 gm/cm^3. The article is reliable in regards to particle physics. If one accepts TOE. However its calculations are based on a far older inflationary model. Still doubt that would be enough for time dilation. Assuming we have a magic telescope to allow us to be an outside observer lol.

 

[Chalnoth]

To be honest with you neither am I. Granted I also cannot find any reliable source with an estimate of the density of the Planch and GUT epoch. Some of the older particle physics articles covering the TOE aspects of these epochs. Place the density around 10^78 gm/cm^3. The article is reliable in regards to particle physics. If one accepts TOE. However its calculations are based on a far older inflationary model. Still doubt that would be enough for time dilation. Assuming we have a magic telescope to allow us to be an outside observer lol.

I'm pretty sure this can be solved by comparing the time coordinate in FRW to proper time. For an observer stationary with respect to the background, those two are the same thing. So yes, there is no time dilation from the expansion.

 

[Mordred]

I agree on that, considering that was one of the higher estimates in any non pop/mass media article I've come across. I've got a huge collection of them as I'm currently self studying early particle physics.

 

[jalak7]

When cosmic background radiation was created the time flow throughout the universe was pretty much the same everywhere, right? So if we made a clock based on that and called it a universal clock, then would the flow of time in the early universe be slower relative to the universal clock than time flow is today, because of the difference in gravity?

 

[Mordred]

No the gravitational density isn't sufficient to dilate time. Gravitational density time dilation only occurs around massive bodies or near relativistic velocities.
We would see redshift due to expansion which from our observer would look dilated but not due to to the gravitational potential of the radiation era. Remember time dilation is seen by an external observer, time flows normal for an observer in the massive gravitational well.

 

[Chalnoth]

When cosmic background radiation was created the time flow throughout the universe was pretty much the same everywhere, right? So if we made a clock based on that and called it a universal clock, then would the flow of time in the early universe be slower relative to the universal clock than time flow is today, because of the difference in gravity?

I think the problem is that there isn't any way to compare relative time dilation between two different points in time.

 

[Mordred]

Simply put there wouldn't be.

https://www.physicsforums.com/showthread.php?
p=4367783#post4367783

the above thread is similar to this one. Timmdeeg gave a good correlation. One I had completely missed lol.

 

[petm1]

I would think that in the early universe time ticked at the same rate for all clocks, coordinate time was the only time. As the duration of the universe increased the difference between coordinate time of the universe and the proper time of matter began to differ as they aged at about the same rate. The simultaneous moment of coordinate time, one clock for the universe, as compared with the simultaneous motion of a single clock within it.

 

[Mordred]

To my understanding even much higher matter density of the universe in the past wouldn't cause gravitational time dilation, because in contrast to Schwarzschild metric the gravitational potential in the FRW model is isotropic. May be this wording isn't correct. What I mean is that as long as we keep the picture that the redshift is due to expansion the density plays no role.

If a particular De-Sitter (matter removed) time slice has no gravity wells to cause a redshift. That lack of dilation cannot be seen in another time slice. So the only measurable difference in regards to redshift would be due to expansion. Also keep in mind the universal energy-density at any time after the inflationary epoch is not enough to cause a dilation. Not that it matters given the above.

 

[timmdeeg]

If a particular De-Sitter (matter removed) time slice has no gravity wells to cause a redshift. That lack of dilation cannot be seen in another time slice. So the only measurable difference in regards to redshift would be due to expansion. Also keep in mind the universal energy-density at any time after the inflationary epoch is not enough to cause a dilation.

Hi Mordred, the cosmological redshift/time dilation is directly related to the scale factor and to the special relativistic Doppler formula in the empty case, resp. Thus we fortunately don't have to care about things like time slices, energy density and a certain epoch. Indirectly yes, as the dynamics depend on energy density, pressure and lambda.

 

[timmdeeg]

I would think that in the early universe time ticked at the same rate for all clocks, coordinate time was the only time. As the duration of the universe increased the difference between coordinate time of the universe and the proper time of matter began to differ as they aged at about the same rate. The simultaneous moment of coordinate time, one clock for the universe, as compared with the simultaneous motion of a single clock within it.

I think the distinction proper time vs. coordinate time is not related to how in which epoch the universe develops. As soon as there is a distance, there is relativity, means there is proper time, which is invariant and coordinate time, which isn't.

 

[petm1]

At some point in the smaller denser hotter past all the makings for all of our clocks were local and ticking at the same rate.

 

[timmdeeg]

At some point in the smaller denser hotter past all the makings for all of our clocks were local and ticking at the same rate.

I am not sure, what you want to say. Perhaps this is of some help. Coordinate/proper time is not related to density.

 

[petm1]

Entropy of the universe goes from the order of one simultaneous event, the same for all future clocks, to the disorder of differences between clocks, as viewed via photons, counting their own simultaneous existence.