Are we certain that we are measuring speed of acceleration with the Red Shift?

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Offline Joe L. Ogan

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Are we absolutely certain that we are measuring speed of acceleration of expansion of the Universe with the Red Shift?  If the Cosmological Constant (Dark Energy)is everywhere, what keeps it from pushing back on the other side of a Galaxy?  How could it force galaxies at greater distance to accelerate at faster speed?  Some of these things beg the question as far as I am concerned.  Thanks for comments.  Joe L. Ogan

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Offline PhysBang

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Redshift measures the rate of expansion of the universe. There is nothing pushing on galaxies, redshift is representative of a change in the geometry of the space in which the galaxies are sitting. Looking at the redshifts of galaxies over a range of distances gives us a measurement of the change in the rate of expansion. This provides a measurement of the cosmological constant.

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Ethos

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 redshift is representative of a change in the geometry of the space in which the galaxies are sitting.

If that is true, and I'm not saying it isn't, then the space between particles is also expanding. If the very fabric itself is expanding, then even the space within particles is doing the same. There is a theory about this expansion that suggests that the expansion of the fabric is the very cause for gravity. I have yet to hear anyone offer a good reason why, the expansion of the fabric is accepted and the expansion of matter itself is not. For the record, I'm not supporting the expansion theory of matter myself, I just want to hear the reason why physicists don't accept both theories when they accept the theory about fabric expansion.

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Ethos

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I have a specific reason for asking this question. Either one believes in expansion of the fabric or they don't. No two ways about it. And if one believes in an expansion of the fabric, they should also support the expansion model of matter. You can't have one without the other.

Being a nonsupporter of the expansion theory of matter, I must also reject the fabric expansion model.

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Offline Joe L. Ogan

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Redshift measures the rate of expansion of the universe. There is nothing pushing on galaxies, redshift is representative of a change in the geometry of the space in which the galaxies are sitting. Looking at the redshifts of galaxies over a range of distances gives us a measurement of the change in the rate of expansion. This provides a measurement of the cosmological constant.

At the risk of being censured, please let me explain why I think we are measuring the wrong thing:  Let us think of the Universe being in the shape of a balloon. This is not a realistic concept because the Universe has no outer covering.  But just for the sake of illustration, let us consider Dark Energy as being the air that is being blown in.  As the air is blown in, the diameter increases in length.  Pi(3.1416) times the Diameter equals circumference.  We must measure the diameter.  If it is increasing in length at an accelerated pace, then the Universe is accelerating expansion.  If the diameter is increasing length at a regular rate, there is no increase in acceleration of expansion of the Universe.  Since Dark Energy fills 70+% of space, I believe it would also be outside the expansion hence it would push back as well as push out.  Thanks for comments.  Joe L. Ogan
« Last Edit: 01/01/2010 23:28:40 by Joe L. Ogan »

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Offline graham.d

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The diameter is increasing at an exponential rate even to give Hubble's equation that the velocity is proportional to the distance. Simple calculus:

ds/dt = H.s

s = exp(H.t) - Abstracting away the integration constant.

This is classical of course. The universe should be modelled more elaborately with the "standard cosmological model" (Friedmann–Lemaître–Robertson–Walker model) with modifications to allow for GR effects, the Doppler measurements and the luminosity measurements of young galaxies. I don't see how this can be done with verbal discussion without going into the maths and a reasonable knowledge of 4d vector analysis. It is generally accepted that the FLRW model is reasonable model on a large scale (despite the assumption of isotropy and homogeneity).

This model predicts the behaviour of the universe and has terms that would allow for H to be non-constant. The increased rate of expansion was not an expected result from measurements and there are a number of theories around that try to explain it. It does fit with the equations but these do not give any explanation as to the cause of the non-zero term.

It is a big mistake to think of the universe as a 3d structure, even though popular science tends to show it this way. It leads to erronious thinking. It is better to think of the universe as a 2d being would perceive his world when, instead of being on a flat plane, is on the surface of a sphere where the sphere is expanding exponentially. The FLRW model is a proper mathematical solution for a simplified (though reasonable) model of the universe in 4d. Hard to visualise though!

Space-time is being stretched, according to current thinking, and I guess this will stretch locally too. I would be interested in reference to any papers on the potential effects of this on the atomic scale (it must be very tiny).


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Ethos

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Space-time is being stretched, according to current thinking, and I guess this will stretch locally too. I would be interested in reference to any papers on the potential effects of this on the atomic scale (it must be very tiny).
Absolutely, very tiny indeed. However, when considering the number of particles contained within the earth, this expansion must be  multiplied geometrically. As I said earlier, I don't agree with the material expansion for several reasons. And likewise, I don't agree with the expanding fabric model either. For the simple fact that if the material expansion is not correct, then the universal expansion is also incorrect.

The material expansion theory suggests that because all objects are expanding universally, the combined growth of an object the size of the earth would neccessarily produce an acceleration on the surface resulting in the force of gravity. The logic for this theory also suggests that it would be inpreceptable to the observer because he would also be expanding. The failure with this theory can be easily understood when those associated with it try to explain how this theory incorporates tidal effects. It just dosen't hold water.

Again I must point out, if material expansion is false, then universal expansion is also false. There are a number of theories regarding why we see red shift, many of which don't need universal expansion as a cause. It is true that red shift will be observed when observing luminous objects in recession from our local frame. But that doesn't neccessarily prove that the so-called fabric is expanding. And as for the CBM radiation, and reasons for it's apparent nonhomgenous nature. I prefer to believe that in an eternal universe, my theory of choice BTW, this nonhomgenous representation is a result of the combined stellar radiation brought to us thru the duration of an infinite past. When science talks about a Big Bang, I prefer to view the history of our cosmos as a multiple of Little Bangs, if that makes any sense to you?

In capsule, unless material expansion is correct, universal expansion is a fabricaition to satisfy the unexplainable nature of the cosmos. And I have already given sound reasons why material expansion is also a fabrication.
« Last Edit: 02/01/2010 01:52:16 by Ethos »

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Offline PhysBang

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I have a specific reason for asking this question. Either one believes in expansion of the fabric or they don't. No two ways about it. And if one believes in an expansion of the fabric, they should also support the expansion model of matter. You can't have one without the other.

Being a nonsupporter of the expansion theory of matter, I must also reject the fabric expansion model.
Well, if one actually follows the science, one notes that the expansion of space is a gravitational effect. This effect is overwhelmed in places where there is a great amount of matter, like within galaxies or galaxy clusters, where the kind of phenomena that we normally associate with gravity dominates.

There is a very real difference between the space in between galaxies and the space within galaxies: the density of matter.

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Offline Geezer

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OK folks. Please try to eliminate the editorials from the debate. (So I'm just as bad, but that does not make it right.)

(Geez - Mod)
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Offline yor_on

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To me the expansion of the universe seems to have to do with 'space' growing?

If both matter and space would grow 'together' at a proportional rate, should we still have a redshift? Assuming that those waves would 'grow' similar to the rest of the universe, that means, keeping their wavelength/frequency relative us, as they too should be magnified proportionally. If you see how I think here..

As there is a 'redshift' it seems plausible that 'space' is growing. The alternative would then be that 'space' and 'invariant mass' (matter) would grow but not light? But if it was so we should see light waves 'shrinking' it seems to me? Becoming more 'energetic'.

So maybe we are shrinking :) and the light stays the same ::))

Light and the Expansion of the Universe

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As for the question how something (the outer edges of the universe) moves faster than FTL. Well, they don't, not really :)

If space somehow can 'expand' like if we had an 'point structure' in space where you can visualize every thought point as a 'fountain' letting out new 'points' of space then you will have a situation where all points of space becomes more, growing like the area inside those circles in the water you create as you throw gravel in a pond. But there can be no 'wavefront' to it as every point will beget new points all around it that then, in their turn, should experience the same as soon as they 'exist'.

(And at some limit that would create a situation where the light from afar never will be able to reach us as 'space' then would have grown, and keep on growing, at a rate making it impossible for that light to ever approach us. Actually it seems as if this light then also might become so 'stretched'/red-shifted that it will disappear from our detection too? And if that was correct shouldn't it be testable as this should happen 'everywhere'?)

But if it was so, and light is 'red shifted' due to this, then light must be a part of this 'space' too, do you agree? Like some 'rubber band'  getting stretched as the space grows.

And, if so, perhaps those waves do have to 'travel' between source (sun) and sink (your eye). As this redshift then have to happen between its start and endpoint. So if we accept that idea then not only space grows, but it also directly influences light, growing'/red-shifting it on its way, but not invariant mass?

Why would it be that way?
It seems very complicated.

And what if 'light' doesn't move at all?
What if Feynman's 'many paths' is as true as stated, with the addition of light not traveling at all?
===

But there is something strange in the proposal. If light, as I suggested, do travel and are an integrated part of space, and space is growing why do it 'stretch' instead of just growing with it? Space somehow seems to influence the light just like that 'rubber band' if this is correct, which then seems to say.

1. if this is right then this seems to be a proof of light having an independent relation to space. Like it's an object that space can 'operate' on, but which is of its own.

2, Matter is an even more independent relation of space if it doesn't grow?

3. And light then seems to have a 'motion', it travels.

And that brings us to the two slit experiment and sending one 'photon' at a time and still getting that wave pattern. Which in its turn bring me to 'many paths', The idea that the 'photon' take all paths there is, but with different levels of probability?

If it really does so, and as I see it, this is the best explanation so far. Then it must do so everywhere. What happens with those for us unrealized paths?

Yep, I'm getting confused again :)
And I'm still holding out on light 'traveling' :)

===

And there are some more things that confuse me here.

We know that relative any thought observational point, no matter if it is at near light speed or standing still, light will always be moving at a speed of 'c' relative that point.

And that seems to me contradictory, even though it might not be. It somehow falls down to frames of reference here. If I say that I will put an observer on every new 'point materializing' in this expanding space and then let those watch a light beam, photon, whatever you like to call it, then they all will see it move relative them at 'c', right?

It seems to break down into an awful lot of 'frames of reference' here, doesn't it?
So, would they also see the light redshift?

And there is also the idea with light needing to 'interact' before anything can happen. Which then seem to say that even in a 'perfect vacuum' somewhere, possibly, out there this light still would be able to 'interact' with it, as it must do, if it redshifts due to space expanding?

How does it do it?

And there is something more to it too, but I can't put my finger on it :)




 
« Last Edit: 03/01/2010 01:39:51 by yor_on »
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Offline Geezer

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Yor-on, I think you nailed it.

If indeed "space" is expanding, we would not observe any redshift. That, to me anyway, makes no sense. Redshift can only be associated with an actual change in distance. If space expands, there is no change in distance. (We cannot have it both ways.)

Therefore, the observed redshift cannot be associated with an expansion of space.

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Offline graham.d

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I think, again, that the confusion is with using our limited vocabulary. Space-time is indeed expanding but that does nor necesarily mean that space is "stretching" which is why I would be interested in seeing any paper on the subject. The most accepted cosmological model (FLRW metric) has the universe as a uniform, homogenous and isotropic 3-sphere (a 3-d brane of a 4d hypersphere). This is analogous the 2-d surface of a euclidean 3-d sphere but somewhat less easy to visualise. The dimensions of the sphere are growing exponentially. There are parts of this sphere that may well be beyond our ability to see because they can be thought of as "falling outwards" into an event horizon, however the whole sphere is considered part of the "observable universe" because this is defined as that observable by sets of comoving observers at different positions.

The observable redshift is due to the receding velocity plus gravitational effects. Also at great distances we are also looking back in time (the light may have been emitted in the first 100,000 years of the universe - I think this is as far as we have got) where the space was significantly more curved than it is now so the gravity was strong. These effects are taken into account in plotting the Hubble curve. Even after these factors are accounted for the curve indicates a higher redshift than expected, which is what is sometimes put down as being caused by dark energy. It can be accounted for in the model with a mathematical term but its physical nature is not at all understood.

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Offline PhysBang

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Yor-on, I think you nailed it.

If indeed "space" is expanding, we would not observe any redshift. That, to me anyway, makes no sense. Redshift can only be associated with an actual change in distance. If space expands, there is no change in distance. (We cannot have it both ways.)

Therefore, the observed redshift cannot be associated with an expansion of space.
The expansion of space that causes redshift is an expansion of inter-galactic space relative to the space within galaxies.

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Offline Geezer

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Yor-on, I think you nailed it.

If indeed "space" is expanding, we would not observe any redshift. That, to me anyway, makes no sense. Redshift can only be associated with an actual change in distance. If space expands, there is no change in distance. (We cannot have it both ways.)

Therefore, the observed redshift cannot be associated with an expansion of space.
The expansion of space that causes redshift is an expansion of inter-galactic space relative to the space within galaxies.

Redshift will certainly occur if the distance between our galaxy and a distant galaxy increases. But if the intervening space expands, then it does not seem (to me anyway) that we would observe redshift associated only with the expansion of space. If space itself expands, then distance does not increase with the expansion. The distance is still the same.

As Graham points out, this may just be a vocabulary issue. Would it make more sense to avoid the use of the term "expansion of space"?
« Last Edit: 03/01/2010 22:09:17 by Geezer »
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Offline PhysBang

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Redshift will certainly occur if the distance between our galaxy and a distant galaxy increases. But if the intervening space expands, then it does not seem (to me anyway) that we would observe redshift associated only with the expansion of space. If space itself expands, then distance does not increase with the expansion. The distance is still the same.
I do not know what it means to say that space expands without the distance across that space also expanding. IN any case, when cosmologists talk of space expanding, they talk about the increase in average distance between points of the space.
Quote
As Graham points out, this may just be a vocabulary issue. Would it make more sense to avoid the use of the term "expansion of space"?
It might. But one must be clear that cosmological redshift, according to the best theories, is due to a change in the geometry of space itself, where the distance between galaxies grows greater over time.

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Offline Geezer

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Ah! I think I'm beginning to get it. I'm taking "space expands" to literally mean that the fabric of space-time actually stretches. It sounds as if there is actually an increase in the amount of space between galaxies even though those galaxies have not necessarily travelled through space relative to each other. Could this be described as "spatial growth" instead, or would that be even more confusing?
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Offline Joe L. Ogan

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Ah! I think I'm beginning to get it. I'm taking "space expands" to literally mean that the fabric of space-time actually stretches. It sounds as if there is actually an increase in the amount of space between galaxies even though those galaxies have not necessarily travelled through space relative to each other. Could this be described as "spatial growth" instead, or would that be even more confusing?

How about angular growth?  As I see it we are measuring angular growth.  i.e. If you measure the angular growth at 90degrees, it will show 1 1/2 times the actual growth.  If you measure it at 180 degrees, it will show 2 times the actual growth.  I think that is what we may be measuring with the Red Shift.  Thanks for Comments, Joe L. Ogan
« Last Edit: 04/01/2010 00:25:53 by Joe L. Ogan »

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Offline graham.d

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I don't understand what you mean, Joe. What angles are you measuring?

Geezer, I think the evidence suggests that the space between galaxies is increasing: other galaxies are moving away from our galaxy (on average) and the further away they are the faster they are receding. I got the impression that it was suggested that this motion was because space was being "stretched" and that this would mean some change in the spacial distances that are measured, even down to atomic and sub-atomic levels. I don't understand this idea (hence asking for a reference). I think someone mentioned that our "rulers" would be stretched too so how would we know. I don't think this is a necessary conclusion that results from accepting that space-time was created in a big-bang. If this concept genuinely has some predictive qualities then it would be worth pursuing, but it seems a bit vague. I would like to know more about it though.

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Offline yor_on

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I've had this discussion before, probably most of us have :)

But if space growing in itself is correct and is the reason for light redshifting then space has to grow geometrically and for real. I can't see it any other way?

Also redshift then proves that even when there is nothing there (Vacuum) light still will interact with it?

So why 'many paths' and why can't we see the light 'traveling'. Redshift treat it like a 'substance' malleable by vacuum, doesn't it?
----

To be malleable light and vacuum both most have the property of being 'there'. We know that a vacuum seems to contain 'energy'. After all, it's from there we expect 'virtual particles' to come if I understand it right. So what is this empty space if that is correct. Empty at our macroscopic plane following our 'arrow of time' but under that 'size' looking at it from a quantum mechanic perspective not empty at all.

Looking at it from there the 'arrow' disappears and what we see will be a field seething. and in that field I would expect our 'ordinary' photons to exist too, existing at some sort of equivalence to what we call 'travel' under our macroscopic arrow of time. And that's one of the reasons why I don't think anything travels, just as relativity shows us that our 'living space' isn't a constant geometric feature.

Instead you can change both 'time' and 'distance' just by motion and accelerating. There is no easy way ignoring those facts as I know. And if they are true then 'motion' becomes really remarkable. We know that light have a speed. It's one of the walls binding our universe together 'C'. And we call it the ultimate speed that we can prove. But what if it doesn't travel at all, what would create a universe with our parameters if we assume that both 'size' 'time' and 'speed' are descriptions seen one way inside macroscopic SpaceTime and a totally different 'outside' f ex. Plank scales?

« Last Edit: 04/01/2010 13:39:38 by yor_on »
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Offline Joe L. Ogan

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I don't understand what you mean, Joe. What angles are you measuring?

Geezer, I think the evidence suggests that the space between galaxies is increasing: other galaxies are moving away from our galaxy (on average) and the further away they are the faster they are receding. I got the impression that it was suggested that this motion was because space was being "stretched" and that this would mean some change in the spacial distances that are measured, even down to atomic and sub-atomic levels. I don't understand this idea (hence asking for a reference). I think someone mentioned that our "rulers" would be stretched too so how would we know. I don't think this is a necessary conclusion that results from accepting that space-time was created in a big-bang. If this concept genuinely has some predictive qualities then it would be worth pursuing, but it seems a bit vague. I would like to know more about it though.

Hi, graham.d, I recognize that my thought may be wrong, but let me try to explain:  Let us call the Big Bang "A", Let us call the earth "B", 90degrees away from "A" let us call that "C", 180degrees away from "A", let us call that "D". At the moment of the Big Bang, "B". "C", and"D". left simultaneously.  Since Earth is the point we are measuring from, when we reach a point of measurement, we look back and we have travelled one light year.  At the same time, we look at "C", it is 1 1/2 light years away from us.  We look at "D" and it is 2 light years away from us.  I hope this clears up my concept.  Thanks for comments.  Joe L. Ogan
« Last Edit: 04/01/2010 13:37:40 by Joe L. Ogan »

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Offline yor_on

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What you are describing is a circle right? 360 degrees all around. And then A here (the BB) becomes your 'center'?

Or how do you see it?
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Offline yor_on

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If I get you right you let BCD leave that 'center' in different directions and when measured from B you will find that C and D having different distances from us (B).

That is correct, but how do you see it explaining redshift?
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Offline Joe L. Ogan

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I  am not trying to explain Red Shift but that is what I think Red Shift is measuring. Thanks, Joe L. Ogan

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Offline yor_on

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To make it work you would have to assume that all points of measurement are the center, with all other 'objects' then moving from them, and to do that would be the same as a 'space' expanding it seems to me?

Also, redshift isn't a continuous smooth motion. As galaxies distance increase the redshift seems to come in 'jumps' similar to 'black body radiation'.
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Offline graham.d

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Joe, you are looking at 3 points radiating out at the same speed from some "big-bang" point. One is us as an observer (B), one is moving out at right angles (C) and the othe other is moving diametrically away (D) on the other side of the start point (A). In fact the angle we view between A and C does not change from 45 degrees (at least in Euclidean space) and the distance B to C is sqrt(2) Lyears when C to A is 1 Lyear (again assuming Euclidean space).

I still do not see how this relates to redshift except in a normal way in that the distances between the bodies are increasing linearly and that the velocity vector (in the reverse direction to the emitted light) will be proportional to the direct distance between the bodies.

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Offline yor_on

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Maybe I should clarify that :) Even I found it strange, rereading it.

If you let the Big Bangs center be in all possible 'points' inside SpaceTime simultaneously  then you might have the possibility of being able to say that the light, as seen from 'above' (as a whole) would redshift as we then have an expanding universe in every point, but on the other hand, that would include mass too.

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