Time in Early Universe

[XFool]

Scientists see early universe in slow-motion for first time

BBC News

Scientists have observed the early universe running "five times slower" for the first time.

[ursaminortaur]

Scientists see early universe in slow-motion for first time

BBC News

Scientists have observed the early universe running "five times slower" for the first time.

But it is important to realise that time wasn't actually running slower in the early universe it only appears slower from our point of view because such distant galaxies appear to be moving away from us at high speed because of the expansion of the universe.

https://www.universetoday.com/162285/the-early-universe-ran-in-slow-motion/

As special relativity shows, the measure of any two clocks depends on their motion relative to each other. The greater their relative speed, the slower each clock is relative to each other. So, since we see distant galaxies speeding away from us, we should also see time move more slowly. Right?

While that is true, we should be careful not to confuse what is going on. One of the central ideas to note is that each observer will experience time at the standard rate. Look at your watch while speeding along in a rocket, and the seconds will tick away just as they always do. The same is true for an observer on Earth. It’s only when an observer on Earth and on a speeding rocket compare their watches that things get confusing. Each observer thinks the other has a slow watch.

The other thing to keep in mind is that special relativity doesn’t apply globally when things like gravity and dark energy come into play. For that, you need general relativity, but the results are much the same. In the case of distant galaxies, they aren’t speeding away from us through space like a rocket. Instead, space itself is expanding between us and those galaxies. Because of this cosmic expansion, the light from them is shifted to the red, hence their high redshift. This cosmic expansion also stretches the apparent time between ticks and tocks, making the rate of time in those galaxies appear slower to us.
.
.
.
The study was able to extend time dilation observations all the way back to when the universe was just a billion years old. From our perspective, a second from that epoch appears to last five seconds. This agrees with general relativity and the standard cosmological model

[odysseus2000]

Scientists see early universe in slow-motion for first time

BBC News

Scientists have observed the early universe running "five times slower" for the first time.

But it is important to realise that time wasn't actually running slower in the early universe it only appears slower from our point of view because such distant galaxies appear to be moving away from us at high speed because of the expansion of the universe.

https://www.universetoday.com/162285/the-early-universe-ran-in-slow-motion/

As special relativity shows, the measure of any two clocks depends on their motion relative to each other. The greater their relative speed, the slower each clock is relative to each other. So, since we see distant galaxies speeding away from us, we should also see time move more slowly. Right?

While that is true, we should be careful not to confuse what is going on. One of the central ideas to note is that each observer will experience time at the standard rate. Look at your watch while speeding along in a rocket, and the seconds will tick away just as they always do. The same is true for an observer on Earth. It’s only when an observer on Earth and on a speeding rocket compare their watches that things get confusing. Each observer thinks the other has a slow watch.

The other thing to keep in mind is that special relativity doesn’t apply globally when things like gravity and dark energy come into play. For that, you need general relativity, but the results are much the same. In the case of distant galaxies, they aren’t speeding away from us through space like a rocket. Instead, space itself is expanding between us and those galaxies. Because of this cosmic expansion, the light from them is shifted to the red, hence their high redshift. This cosmic expansion also stretches the apparent time between ticks and tocks, making the rate of time in those galaxies appear slower to us.
.
.
.
The study was able to extend time dilation observations all the way back to when the universe was just a billion years old. From our perspective, a second from that epoch appears to last five seconds. This agrees with general relativity and the standard cosmological model

I can see where this analysis comes from, but it does not seem to include the effects of inflation which we believe happened in the early universe with potential observable consequences even after the longish times referred to here which complicates an interpretation based on general relativity and if space is expanding as argued, then it is not clear to me that the velocity of light will remain constant and if not then arguments on Doppler shifted light are troubled: is the Doppler shift due to the recession velocity as normally argued or the effects of space changing and/or both?

It seems to me that this analysis is way too simplistic and needs quantitative support.

Regards,

[ursaminortaur]

But it is important to realise that time wasn't actually running slower in the early universe it only appears slower from our point of view because such distant galaxies appear to be moving away from us at high speed because of the expansion of the universe.

https://www.universetoday.com/162285/the-early-universe-ran-in-slow-motion/

I can see where this analysis comes from, but it does not seem to include the effects of inflation which we believe happened in the early universe with potential observable consequences even after the longish times referred to here which complicates an interpretation based on general relativity and if space is expanding as argued, then it is not clear to me that the velocity of light will remain constant and if not then arguments on Doppler shifted light are troubled: is the Doppler shift due to the recession velocity as normally argued or the effects of space changing and/or both?

It seems to me that this analysis is way too simplistic and needs quantitative support.

Regards,

The inflationary period ended about 10^-32 seconds after the big bang whereas this is looking at a result from quasars from a billion years after the big bang.

https://en.wikipedia.org/wiki/Inflation_(cosmology)

In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch is believed to have lasted from 10−36 seconds to between 10−33 and 10−32 seconds after the Big Bang. Following the inflationary period, the universe continued to expand, but at a slower rate. The acceleration of this expansion due to dark energy began after the universe was already over 7.7 billion years old (5.4 billion years ago).[1]

All our current theories are based on the speed of light having remained constant since the early universe. The redshift effect doesn't change the speed of light but reduces the frequency of that light to compensate for the increase in wavelength. The speed of light in Maxwell's equations depends on the permeability and permittivity of the vacuum thus any change in the speed of light would require those values to change affecting the fine structure constant and the electromagnetic attraction between charged particles. A variable speed of light in the early universe can't be ruled out but any change would have to be fairly small.

For really distant galaxies the red shift will pretty much entirely be caused by the expansion of space with any actual motion by the galaxy either towards us or away from us being entirely swamped.

[XFool]

The inflationary period ended about 10^-32 seconds after the big bang whereas this is looking at a result from quasars from a billion years after the big bang.

All our current theories are based on the speed of light having remained constant since the early universe. The redshift effect doesn't change the speed of light but reduces the frequency of that light to compensate for the increase in wavelength. The speed of light in Maxwell's equations depends on the permeability and permittivity of the vacuum thus any change in the speed of light would require those values to change affecting the fine structure constant and the electromagnetic attraction between charged particles. A variable speed of light in the early universe can't be ruled out but any change would have to be fairly small.

Thanks for the clarification.

[odysseus2000]

Yes, I am aware when inflation is supposed to have ended, but I am wondering if its effect should be seen in distributions of matter and/or space time even after a long period. If so it should show in the most distant galaxies.

As I understand red shift, the data says that the further the galaxy the faster it is moving away from us as determined by increased red shift (Relativistic Doppler effect), not as far as I know by an expansion of space.

However, one also sees an increasing red, not a constant red shift, which is put down to the effects of dark energy, accelerating distant galaxies although a changing velocity of light would also have similar effects.

I am unclear if some or all of these observations could be consistent with a change in the relation between space and time, that would show as a changing velocity of light. As far as I am aware it would be difficult just from observation to state that the velocity of light has, since inflation, always been constant. We already know that there are asymmetries in what we measure for example the abundance of matter over anti-matter and perhaps there have been variations in the two constants (Epsilon_0 and Mu_0) that are currently derived from defining the velocity of light as a constant:

https://www.bipm.org/en/measurement-uni ... -constants

There have been various theoretical suggestions that the velocity of light may change in our time, but as far as I know no experiment has ever shown this to be happening which has allowed the velocity of light to be defined as a constant. I don't care much for the definition of an experimentally measured quantity to be a constant, but it is what has been done since 2018.

Regards,

[ursaminortaur]

Yes, I am aware when inflation is supposed to have ended, but I am wondering if its effect should be seen in distributions of matter and/or space time even after a long period. If so it should show in the most distant galaxies.

As I understand red shift, the data says that the further the galaxy the faster it is moving away from us as determined by increased red shift (Relativistic Doppler effect), not as far as I know by an expansion of space.

Inflation magnified quantum fluctuations of density which show up 380,000 years later in the CMB (when the universe became transparent to radiation) as very slightly warmer or colder areas. These differences in density then determined where galaxies formed.


As I said the movement of distant galaxies through space is swamped by the apparent movement caused by the expansion of space. The usual analogy used to explain this is blowing up a balloon. The surface of the two dimensional surface of the balloon representing our three dimensional universe with dots painted on the balloon to represent the positions of galaxies. If you imagine say four galaxies in a line on that surface each one unit away from its neighbours with the first galaxy being our milky way ( call them say M,N,O and P) then the distances from M our galaxy are

M N O P

0 1 2 3

If one time unit later the balloon has doubled in size then the distances become

0 2 4 6

and N will appeared to have moved away from M at a speed of 1 ( change of distance divided by amount of time : (2 - 1)/1 ), O will appear to have moved away at a speed of 2 and P will have appeared to have moved away at a speed of 3. None have actually moved on the surface of the balloon but the balloon's expansion makes it appear that the further away a galaxy is the faster it is moving away. This apparent movement away from us which is actually the space expanding is what is seen as a red shift. This is what is meant by "the further the galaxy the faster it is moving away from us as determined by increased red shift". As with the dots on the balloon the distant galaxy may not be moving at all through space but if they are moving it will be at similar velocities to how our milky way galaxy is moving and will have little effect on the redshift compared to the expansion of space.

[mc2fool]

As I said the movement of distant galaxies through space is swamped by the apparent movement caused by the expansion of space. The usual analogy used to explain this is blowing up a balloon. The surface of the two dimensional surface of the balloon representing our three dimensional universe with dots painted on the balloon to represent the positions of galaxies.

One cosmology tutor I knew pooh-poohed the balloon analogy, 'cos of its two dimensionality, and used a fruit loaf analogy instead -- as the dough rises all the raisins "move" away from each other, in three dimensions.

[swill453]

One cosmology tutor I knew pooh-poohed the balloon analogy, 'cos of its two dimensionality, and used a fruit loaf analogy instead -- as the dough rises all the raisins "move" away from each other, in three dimensions.

Or like explosive particles might in a, er, big bang?

Scott.

[mc2fool]

One cosmology tutor I knew pooh-poohed the balloon analogy, 'cos of its two dimensionality, and used a fruit loaf analogy instead -- as the dough rises all the raisins "move" away from each other, in three dimensions.

Or like explosive particles might in a, er, big bang?

No, not like explosive particles, which in an explosion do actually move themselves.

The term "Big Bang" is unfortunate 'cos it gives the image of and is often misunderstood as an explosion ejecting matter outwards, like a bomb, but actually Big Bang refers to the rapid expansion of space itself, and it occurred everywhere in space simultaneously.

So, yes, the current expansion of the universe is a continuation of the Big Bang process, so the fruit loaf analogy applies all (well, most ) of the way back to it, but it's not like particles in an explosion.

[XFool]

Yes, I am aware when inflation is supposed to have ended, but I am wondering if its effect should be seen in distributions of matter and/or space time even after a long period. If so it should show in the most distant galaxies.

I thought it did, in the microwave background radiation?

As I understand red shift, the data says that the further the galaxy the faster it is moving away from us as determined by increased red shift (Relativistic Doppler effect), not as far as I know by an expansion of space.

My understanding (such as it is) has always been that the relative motion of increasingly distant galaxies is caused by the expansion of space.

There have been various theoretical suggestions that the velocity of light may change in our time, but as far as I know no experiment has ever shown this to be happening which has allowed the velocity of light to be defined as a constant. I don't care much for the definition of an experimentally measured quantity to be a constant, but it is what has been done since 2018.

Though, where that is in relation to defining the standards for measuring physical constants, for immediate practical purposes it surely only needs to be sensibly true locally, in space and time?

[ursaminortaur]

Or like explosive particles might in a, er, big bang?

No, not like explosive particles, which in an explosion do actually move themselves.

The term "Big Bang" is unfortunate 'cos it gives the image of and is often misunderstood as an explosion ejecting matter outwards, like a bomb, but actually Big Bang refers to the rapid expansion of space itself, and it occurred everywhere in space simultaneously.

So, yes, the current expansion of the universe is a continuation of the Big Bang process, so the fruit loaf analogy applies all (well, most ) of the way back to it, but it's not like particles in an explosion.

The term "Big Bang" was coined by Fred Hoyle who was an opponent of the theory and it was said by others that he coined the name to try and ridicule the theory. Unfortunately as has happened in the past with other intended terms of abuse ( eg imaginary numbers) the name stuck.

https://en.wikipedia.org/wiki/Fred_Hoyle

Hoyle was a strong critic of the Big Bang. He coined the term "Big Bang" on BBC radio's Third Programme broadcast on 28 March 1949.[26] It was said by George Gamow and his opponents that Hoyle intended to be pejorative, and the script from which he read aloud was interpreted by his opponents to be "vain, one-sided, insulting, not worthy of the BBC".[27] Hoyle explicitly denied that he was being insulting and said it was just a striking image meant to emphasize the difference between the two theories for the radio audience.[28] In another BBC interview, he said, "The reason why scientists like the "big bang" is because they are overshadowed by the Book of Genesis. It is deep within the psyche of most scientists to believe in the first page of Genesis".[29]

[scotia]

Hoyle was a strong critic of the Big Bang. He coined the term "Big Bang" on BBC radio's Third Programme broadcast on 28 March 1949.[26] It was said by George Gamow and his opponents that Hoyle intended to be pejorative, and the script from which he read aloud was interpreted by his opponents to be "vain, one-sided, insulting, not worthy of the BBC".

Dad bought the 1950 edition of Fred Hoyle's book based on the Third Program broadcasts (The Nature of the Universe), and I read it when I was a bit older. Fred Hoyle expounded very interesting views - not all of which were proven to be correct, but his attraction was his original thought on a range of topics - which often rocked the boat on existing scientific theories. I never felt he was vain or insulting.
But he never got everything correct - even sometimes when he concurred with established ideas which are now widely discredited. Looking at the book's Notes, he wrote Nor do I think that any plausibility can be attached to Wegener's idea of continental drift.

[scrumpyjack]

and Hawking rather tore Fred Hoyle apart.

https://www.navhindtimes.in/2018/03/18/ ... red-hoyle/

[CliffEdge]

The universe is not expanding in three dimensions.

[ursaminortaur]

The universe is not expanding in three dimensions.

Observations show distant galaxies having increased redshifts with distance in all directions hence the universe does appear to be expanding in three dimensions as time increases.

Of course if string theory is correct there may be more than three spatial dimensions however if as expected these extra dimensions are curled up tightly then they can't have expanded very much otherwise they would have grown to such an extent that we would have noticed them. Alternatively another interpretation of string theory posits that our universe exists on a membrane embedded in a higher dimensional bulk possibly along with other membrane universes. But we have no evidence, even if we accept that this higher dimensional bulk exists, that distances between our universe and others in this bulk are increasing (ie we have no evidence that expansion is occuring in the higher dimensions of this bulk).

[CliffEdge]

The universe is not expanding in three dimensions.

Observations show distant galaxies having increased redshifts with distance in all directions hence the universe does appear to be expanding in three dimensions as time increases.

Of course if string theory is correct there may be more than three spatial dimensions however if as expected these extra dimensions are curled up tightly then they can't have expanded very much otherwise they would have grown to such an extent that we would have noticed them. Alternatively another interpretation of string theory posits that our universe exists on a membrane embedded in a higher dimensional bulk possibly along with other membrane universes. But we have no evidence, even if we accept that this higher dimensional bulk exists, that distances between our universe and others in this bulk are increasing (ie we have no evidence that expansion is occuring in the higher dimensions of this bulk).

Yes, the three dimensions of the universe are expanding equally in all directions - effectively it as though the universe is expanding in a fourth dimension as you say - though that is not standard belief it is useful as a way of avoiding the common misconception among the general population of the universe expanding in three dimensions which would imply the location of a detectable centre.

[ursaminortaur]

Observations show distant galaxies having increased redshifts with distance in all directions hence the universe does appear to be expanding in three dimensions as time increases.

Of course if string theory is correct there may be more than three spatial dimensions however if as expected these extra dimensions are curled up tightly then they can't have expanded very much otherwise they would have grown to such an extent that we would have noticed them. Alternatively another interpretation of string theory posits that our universe exists on a membrane embedded in a higher dimensional bulk possibly along with other membrane universes. But we have no evidence, even if we accept that this higher dimensional bulk exists, that distances between our universe and others in this bulk are increasing (ie we have no evidence that expansion is occuring in the higher dimensions of this bulk).

Yes, the three dimensions of the universe are expanding equally in all directions - effectively it as though the universe is expanding in a fourth dimension as you say - though that is not standard belief it is useful as a way of avoiding the common misconception among the general population of the universe expanding in three dimensions which would imply the location of a detectable centre.

Not quite what I was saying. The fourth dimension that the universe is expanding into is time rather than another spacial dimension and for the observable universe there is a centre but it is back at the beginning of time at the big bang.

If the universe beyond the observable universe is spatially infinite in extent then it has always been spatially infinite and although it is expanding in the time direction it would still remain infinite in extent and there would be no centre even in the past (the big bang just being something that happened in this particular region which became our observable universe - one model for that being eternal inflation in an infinite universe).

[CliffEdge]

Yes, the three dimensions of the universe are expanding equally in all directions - effectively it as though the universe is expanding in a fourth dimension as you say - though that is not standard belief it is useful as a way of avoiding the common misconception among the general population of the universe expanding in three dimensions which would imply the location of a detectable centre.

Not quite what I was saying. The fourth dimension that the universe is expanding into is time rather than another spacial dimension and for the observable universe there is a centre but it is back at the beginning of time at the big bang.

If the universe beyond the observable universe is spatially infinite in extent then it has always been spatially infinite and although it is expanding in the time direction it would still remain infinite in extent and there would be no centre even in the past (the big bang just being something that happened in this particular region which became our observable universe - one model for that being eternal inflation in an infinite universe).

No there is not an observable centre. You like many others have misunderstood.

[ursaminortaur]

Not quite what I was saying. The fourth dimension that the universe is expanding into is time rather than another spacial dimension and for the observable universe there is a centre but it is back at the beginning of time at the big bang.

If the universe beyond the observable universe is spatially infinite in extent then it has always been spatially infinite and although it is expanding in the time direction it would still remain infinite in extent and there would be no centre even in the past (the big bang just being something that happened in this particular region which became our observable universe - one model for that being eternal inflation in an infinite universe).

No there is not an observable centre. You like many others have misunderstood.

I'm not sure what you mean by "observable" centre. If you just mean that you cannot point your telescope at any unique spot and say that that is the centre from which everything else is moving apart then that is trivially true. It may appear that all the distant galaxies are rushing away from us and the milky way making us the centre but someone on a planet in one of those distant galaxies would also see all the distant galaxies rushing away from them like they were the centre.

However there is a centre in the past for the observable universe but it is a trivial solution as it is a single point, a singularity, which contains the whole observable universe at one point at one particular time - that of the big bang at the beginning of time. At no other time is there a centre to the observable universe *. In the balloon analogy the centre would be the centre of the spherical balloon rather than a point on its present surface with the radius of the balloon being the time dimension - and that centre would only be on the surface (trivially) at time zero.

* To complicate matters when we look vast distances in space we are looking back in time but even if we could look back far enough to see the big bang it would appear to be in every direction (as does the CMB) rather than appearing at one point because at the time of the big bang everything in the observable universe was in that singularity - the big bang happened everywhere in the observable universe.