Cosmological principle and quasar distribution

[TrickyDicky]

Our cosmology model follows the cosmological principle according to which we are not in a privileged place in the universe and there is homogeneity, but if you take a look at the distribution of quasars in the universe there seems to be a "quasar spherical void" roughly one billion lightyears in radius around us. There seems to be a big flaw in the homogeneity of the universe precisely with center in us.
This doesn't seem to agree very well with the Cosmological principle in which our cosmology is based together with GR. Is this something to worry about? Or it doesn't really matter?

 

[Jonathan Scott]

Our cosmology model follows the cosmological principle according to which we are not in a privileged place in the universe and there is homogeneity, but if you take a look at the distribution of quasars in the universe there seems to be a "quasar spherical void" roughly one billion lightyears in radius around us. There seems to be a big flaw in the homogeneity of the universe precisely with center in us.
This doesn't seem to agree very well with the Cosmological principle in which our cosmology is based together with GR. Is this something to worry about? Or it doesn't really matter?

The standard explanation is that this relates to time, in that the conditions for forming new quasars effectively cease after the universe reaches a certain age.

 

[TrickyDicky]

The standard explanation is that this relates to time, in that the conditions for forming new quasars effectively cease after the universe reaches a certain age.

Really? it doesn't sound very convincing, rather looks like an ad hoc justification without any base.
In fact that kind of explanation makes the cosmological principle unfalsifiable, since any deviation from the principle can be blamed on "evolution" causes.

 

[bcrowell]

Really? it doesn't sound very convincing, rather looks like an ad hoc justification without any base.
In fact that kind of explanation makes the cosmological principle unfalsifiable, since any deviation from the principle can be blamed on "evolution" causes.

Actually this kind of observation is an observational test that big-bang cosmology passes and that steady-state cosmology fails. If we observed that the universe looked the same at all redshifts, then it would falsify big-bang cosmology and support steady-state.

The cosmological principle is far from unfalsifiable. There is some good material on the topic here: http://en.wikipedia.org/wiki/Cosmological_principle

 

[Vanadium 50]

We know a 100,000 year old universe looks different than a 13.7Gy old universe. Why should a 13.7 Gy universe look like a 10, 8 or 5 Gy old universe?

 

[TrickyDicky]

We know a 100,000 year old universe looks different than a 13.7Gy old universe. Why should a 13.7 Gy universe look like a 10, 8 or 5 Gy old universe?

The Cosmological principle? the Generalized Copernican principle? The very principles FRW cosmology is based on. It all comes down to homogeneity at large spatial distances. People seems to forget selectively that Gly is also a spatial distance measure, not just a time span.
The way you depict it with the universe looking very different at different radial distances from us is against the Cosmological principle among other things because it locates us at the center of that particular evolution and our cosmology is based on the opposite assumption:"no privileged observer".
Homogeneity means that every observer in the universe must observe approximately the same at large distances, don't you see something odd if every observer no matter how near or far from us must see the same evolution (the universe looking a certain way at different radial distances)? Either there is homogeneity or a different evolution for every observer located sufficiently far from other observers. I'm afraid you can't coherently have the two scenarios at the same time.

 

[Jonathan Scott]

The Cosmological principle? the Generalized Copernican principle? The very principles FRW cosmology is based on. It all comes down to homogeneity at large spatial distances. People seems to forget selectively that Gly is also a spatial distance measure, not just a time span.
The way you depict it with the universe looking very different at different radial distances from us is against the Cosmological principle among other things because it locates us at the center of that particular evolution and our cosmology is based on the opposite assumption:"no privileged observer".
Homogeneity means that every observer in the universe must observe approximately the same at large distances, don't you see something odd if every observer no matter how near or far from us must see the same evolution (the universe looking a certain way at different radial distances)? Either there is homogeneity or a different evolution for every observer located sufficiently far from other observers. I'm afraid you can't coherently have the two scenarios at the same time.

Yes you can. If quasars died out everywhere around the same time, then everyone existing at the present day will see the same effect of a spherical void, regardless of location.

 

[TrickyDicky]

Yes you can. If quasars died out everywhere around the same time, then everyone existing at the present day will see the same effect of a spherical void, regardless of location.

It is not so easy to define a "same time" and "present day" for distant observers in GR.
If you set the time all quasars happened to die out about 1GY ago from our location, how does that translate to a galaxy 13.2 Gly from us (like the last one discovered recently:see WP), supposing it is still existing at present day from our point of view, that is 13,2 Gy after the light we see left that galaxy. Would you say that if we were observing with our telescopes from that location the quasar would ceased to exist also at a radius of 1Gly? Or would we observe a different evolution?

 

[Chalnoth]

Quasars are a result of lots of gas falling into the supermassive black holes at the centers of galaxies. Once the gas is used up, the quasars die out. So, there were lots of quasars when galaxies were first forming. But now they are far less common because there aren't as many galaxies with enough gas in their cores.

 

[TrickyDicky]

Quasars are a result of lots of gas falling into the supermassive black holes at the centers of galaxies. Once the gas is used up, the quasars die out. So, there were lots of quasars when galaxies were first forming. But now they are far less common because there aren't as many galaxies with enough gas in their cores.

And I was saying that "now" is not a meaningful global concept in GR, it only has meaning as cosmic time for us as observers who choose a certain preferred frame of reference, but our "now" can not be compared with "now" at cosmological distances,(that is if you use GR as the theory to understand the universe and consider it a curved manifold). So our chronology doesn't have to be the same as the chronology as seen from a distant point from our POV.
So it is easy to see that spatial homogeneity is not a valid concept in a curved manifold for different points sufficiently distant between each other, because their timescales can't be meaningfully compared.
There is no way you can claim (if you know something about relativity) that all quasars died out approximately at the "same time" for all possible observers in a curved spacetime universe. But a cosmological principle that includes spatial homogeneity demands that from any point we should see approximately the same matter distribution (no privileged observer), you seem to imply that from any point in the universe the same matter distributions at different distances should be observed, and I'm saying that that would demand an absolute time, not just a congruence for our POV in our preferred frame.
If there is some specific point where I'm wrong in what I'm saying I would like it to be explained to me.

 

[Jonathan Scott]

And I was saying that "now" is not a meaningful global concept in GR, it only has meaning as cosmic time for us as observers who choose a certain preferred frame of reference, but our "now" can not be compared with "now" at cosmological distances,(that is if you use GR as the theory to understand the universe and consider it a curved manifold). So our chronology doesn't have to be the same as the chronology as seen from a distant point from our POV.
So it is easy to see that spatial homogeneity is not a valid concept in a curved manifold for different points sufficiently distant between each other, because their timescales can't be meaningfully compared.
There is no way you can claim (if you know something about relativity) that all quasars died out approximately at the "same time" for all possible observers in a curved spacetime universe. But a cosmological principle that includes spatial homogeneity demands that from any point we should see approximately the same matter distribution (no privileged observer), you seem to imply that from any point in the universe the same matter distributions at different distances should be observed, and I'm saying that that would demand an absolute time, not just a congruence for our POV in our preferred frame.
If there is some specific point where I'm wrong in what I'm saying I would like it to be explained to me.

On the cosmological scale there is an approximate rest frame everywhere, which is roughly the average frame of the local galaxies. If there were not, galaxy redshifts would not be any use as distance indicators. That means that there is effectively a global time to that level of accuracy.

 

[Jonathan Scott]

I must admit I agree that it seems a bit odd that quasars just happened to be doing fine since the start of the universe - or apparently even before(!), according to some results from very high redshift quasar metallicity values - but then all ran out everywhere quite recently, given how non-uniform their properties seem in other ways (with unexpectedly weak correlations between brightness, redshifts and spectral characteristics).

However, it doesn't violate the cosmological principle.

 

[Vanadium 50]

The Cosmological Principle does not say that the universe looks the same at all times.

 

[TrickyDicky]

On the cosmological scale there is an approximate rest frame everywhere, which is roughly the average frame of the local galaxies. If there were not, galaxy redshifts would not be any use as distance indicators. That means that there is effectively a global time to that level of accuracy.

Yes, there is a rest frame, but it is claimed that is just a consequence of a coordinate choice, according to GR we should be able to use a different coordinate choice, with different cosmic time and we would still be able to use galaxy redshift as useful distance indicators from our location (remember redshift is a coordinate-independent measure).
So there is not really a global time that is the same for every distant location in the universe, we can assign a cosmic time for our particular observer position, but that doesn't guarantee you that from a distant position observers share the same "global time", that's impossible to determine in GR because in a curved manifold parallel transport with a connection permits connecting the geometries of nearby points only, it is a local procedure, unlike it is possible in flat spacetime, it doesn't work that way for points separated cosmological distances, where ambiguity is introduced thru path-dependence of the connection. But this connection is defined locally, in order to have a "global time" we would have to have a "global connection, no such thing in GR, it's not possible to define a global connection because in general parallel transport is path dependent, the only spaces with global connections are those with no curvature. If there were really a "global time" we could unambiguously define distant velocities in cosmology but as you might know we can't.

The Cosmological Principle does not say that the universe looks the same at all times.

You're right, it doesn't. From WP: "The cosmological principle is usually stated formally as 'Viewed on a sufficiently large scale, the properties of the Universe are the same for all observers.'... Here "observers" means any observer at any location in the universe...The two testable structural consequences of the cosmological principle are homogeneity and isotropy. Homogeneity means that the same observational evidence is available to observers at different locations in the universe ("the part of the Universe which we can see is a fair sample").
So it doesn't specifically say the universe looks the same at all times, but it does say it looks approximately the same from all locations, right? Now, in a curved spacetime locations separated by large distances don't share the same "global time" as explained above. So if you impose that they should observe fairly the same, you are imposing it for whatever times every location is at. So in an indirect way you are either giving a meaningless homogeneity concept for a curved manifold, or indirectly saying the universe looks the same at all times.

 

[Chalnoth]

And I was saying that "now" is not a meaningful global concept in GR, it only has meaning as cosmic time for us as observers who choose a certain preferred frame of reference, but our "now" can not be compared with "now" at cosmological distances,(that is if you use GR as the theory to understand the universe and consider it a curved manifold). So our chronology doesn't have to be the same as the chronology as seen from a distant point from our POV.

Just define the global time slicing as one in which the CMB temperature is isotropic and the same temperature everywhere. With that definition, what I wrote holds.

 

[TrickyDicky]

Just define the global time slicing as one in which the CMB temperature is isotropic and the same temperature everywhere. With that definition, what I wrote holds.

As i explained in my previous post that time slicing is a local one for each distant location in the universe that allows to have a cosmic time from the limit of the observable universe from each location but that is valid only for that location because in a curved manifold you can't have such global time, that is only possible in a Newtonian univere or in a Minkowski spacetime because both are flat.

 

[Chalnoth]

As i explained in my previous post that time slicing is a local one for each distant location in the universe that allows to have a cosmic time from the limit of the observable universe from each location but that is valid only for that location because in a curved manifold you can't have such global time, that is only possible in a Newtonian univere or in a Minkowski spacetime because both are flat.

No, it's quite global. It is arbitrary, in that there are many other potential choices, but that doesn't mean it isn't a global time slicing.

 

[TrickyDicky]

No, it's quite global. It is arbitrary, in that there are many other potential choices, but that doesn't mean it isn't a global time slicing.

It's global for us, which is not the same as being globally valid for any observer in the universe, people keep mixing properties of flat spaces with those of curved manifolds. And in any case it can't be checked experimentally, so we must go by what the current theory (GR) and differential geometry say, and that is that in a curved manifold there is no way to unambiguously compare cosmic times from distant points in the universe.

 

[Chalnoth]

It's global for us, which is not the same as being globally valid for any observer in the universe, people keep mixing properties of flat spaces with those of curved manifolds. And in any case it can't be checked experimentally, so we must go by what the current theory (GR) and differential geometry say, and that is that in a curved manifold there is no way to unambiguously compare cosmic times from distant points in the universe.

You're not getting me. It's an arbitrary choice, but a perfectly valid one. And in this case it is a choice that would make sense to any sitting on any planet on any galaxy in our universe, because it is directly related to the proper time since the CMB was emitted. It wouldn't be a terribly useful time slicing for an observer moving through our universe with relativistic speed, but then we don't care much about those observers for the purpose of this kind of discussion.

 

[TrickyDicky]

You're not getting me. It's an arbitrary choice, but a perfectly valid one. And in this case it is a choice that would make sense to any sitting on any planet on any galaxy in our universe,

This is perfectly ok, I guess you are missing my point too.

because it is directly related to the proper time since the CMB was emitted.

Proper time depends on the state of motion of the clocks that measure it and I've been saying all along that in GR this can't be ascertained without ambiguity, so you can't compare proper times of points of the universe separated by large distances.

So I'm still not finding arguments to make compatible the peculiar quasar distribution with the cosmological principle.

 

[Chalnoth]

Proper time depends on the state of motion of the clocks that measure it

Yes, but due to the fact that the expansion of the universe tends to dampen motions, this point is irrelevant, so that as far as time dilation is concerned you can effectively consider everything to be stationary with respect to the CMB.

Now, if you want to consider some hypothetical observer moving at relativistic velocities with respect to the CMB, that's fine. But it doesn't apply to any galaxy in the universe.

Edit: Just to put a few numbers on this, our motion with respect to the CMB is about v/c = 0.001. In the densest of clusters, you might get up to around v/c = 0.01, but that is a rarity. That would cause a time dilation of 0.005% with respect to the global time reference frame of the CMB. Certainly measurable if you were careful about it, but irrelevant for nearly all purposes.

 

[dougal217]

The Standard Model depends on the CP (and GR) and although the CP isn't "unfalsifiable" it's also unprovable.

The quasar issue isn't the only problem for the CP. The quadrupole and octupole modes of the WMAP that seem to orient along the ecliptic plane is a problem. The Pioneer anomaly is a problem. Inflation being in tatters doesn't help.

I know of one paper that provides data regarding concentric rings at intervals radiating out... from here, home.

A bounded, finite Universe with a gravitational center would explain a lot of things, and it doesn't require an unprovable CP. But nobody is brave enough to touch it, because of the implications.

 

[Chalnoth]

The Standard Model depends on the CP (and GR) and although the CP isn't "unfalsifiable" it's also unprovable.

Er, what? It is only "unprovable" in the sense that all science is unprovable: proof is something that can never be done in science, since all of science relies upon inductive reasoning which is impossible to ever prove.

The quasar issue isn't the only problem for the CP. The quadrupole and octupole modes of the WMAP that seem to orient along the ecliptic plane is a problem. The Pioneer anomaly is a problem. Inflation being in tatters doesn't help.

The quadrupole and octupole modes of WMAP are well within the expected statistical bounds. See here: http://arxiv.org/abs/1001.4758
They show that all of the "anomalies" seen in the WMAP data are just down to not doing the statistics right.

The Pioneer anomaly is just due to the spacecraft itself and has nothing to do with fundamental physics. The prime suspect is the asymmetrical radiation from the Pioneer probe.

I know of one paper that provides data regarding concentric rings at intervals radiating out... from here, home.

Which paper would this be?

A bounded, finite Universe with a gravitational center would explain a lot of things, and it doesn't require an unprovable CP. But nobody is brave enough to touch it, because of the implications.

A bounded, finite universe with a gravitational center would actually explain precisely nothing about our observations. If anything, our observations were pointing in the other direction, with one of the potential proposed explanations for the accelerated expansion being that we live in an especially underdense region of the universe. However, this view has since been ruled out by observations.

 

[TrickyDicky]

Yes, but due to the fact that the expansion of the universe tends to dampen motions, this point is irrelevant, so that as far as time dilation is concerned you can effectively consider everything to be stationary with respect to the CMB.

Now, if you want to consider some hypothetical observer moving at relativistic velocities with respect to the CMB, that's fine. But it doesn't apply to any galaxy in the universe.

Edit: Just to put a few numbers on this, our motion with respect to the CMB is about v/c = 0.001. In the densest of clusters, you might get up to around v/c = 0.01, but that is a rarity. That would cause a time dilation of 0.005% with respect to the global time reference frame of the CMB. Certainly measurable if you were careful about it, but irrelevant for nearly all purposes.

This seems a bit confusing. You say that expansion "dampens motions", it's the first time I hear it put like that, I thought expansion is exacly the opposite, I mean the reason people in the past thought our universe was static was precisely for the reasons you are giving about the motion of galaxies.
Where you don't seem to realize your argument is contradictory in that if the CMB is a global time reference frame valid for all locations in the universe, and if you at the same time claim all galaxies have irrelevant motions wrt that global frame,because we "can effectively consider everything to be stationary with respect to the CMB", you are directly shooting down expansion.
Besides you can't assert that a frame is arbitrary and globally valid for all points in the universe at the same time. An arbitrary choice of frame is perfectly valid for any location, but if all locations share the CMB as a valid rest frame, then you are imposing an absolute frame in GR, I'm not sure this is possible. You can't have your cake and eat it too. Either the CMB is just a local arbitrary valid reference frame, or it's a global reference frame, in this case global means absolute, because if a reference frame can be shared by all points in a manifold so that as you are doing in your post you can assign proper velocities to galaxies located at any point in the manifold based on a shared referenced frame (CMB), you are basically describing a Minkowski spacetime.
So I don't know if you are really sure about your arguments or you are not taking very seriously this discussion.

 

[Chalnoth]

This seems a bit confusing. You say that expansion "dampens motions", it's the first time I hear it put like that, I thought expansion is exacly the opposite, I mean the reason people in the past thought our universe was static was precisely for the reasons you are giving about the motion of galaxies.

The overall expansion tends to dampen motions relative to that expansion. Basically, if you are moving away from the Earth (for instance) in some direction at high velocity, you will be moving towards other stuff that is moving away from the Earth. Over time, you'll slowly catch up to stuff that is moving faster and faster, which, in the end, means that your relative speed compared to the expansion goes down.

This overall expansion, then, sets a global rest frame that everything is drawn towards. It is with respect to this global rest frame that we can sensibly talk about a global time.

 

[Jonathan Scott]

Besides you can't assert that a frame is arbitrary and globally valid for all points in the universe at the same time. An arbitrary choice of frame is perfectly valid for any location, but if all locations share the CMB as a valid rest frame, then you are imposing an absolute frame in GR, I'm not sure this is possible.

No-one is trying to define a relativistically synchronized time coordinate across the universe. What we are saying is that there is a sufficiently consistent global concept of "proper time since the big bang for a slow-moving observer", for example relative to the CMB or local galaxies.

Expansion of the universe means that the CMB or local galaxy rest frame is different at different locations, and local motions could make a little difference too, but remember that the fractional effect of speed on time rate is about (1/2) (v^2/c^2) so even 1% of the speed of light would only have an effect of 0.005% on the time rate.

 

[TrickyDicky]

The overall expansion tends to dampen motions relative to that expansion. Basically, if you are moving away from the Earth (for instance) in some direction at high velocity, you will be moving towards other stuff that is moving away from the Earth. Over time, you'll slowly catch up to stuff that is moving faster and faster, which, in the end, means that your relative speed compared to the expansion goes down.

This overall expansion, then, sets a global rest frame that everything is drawn towards. It is with respect to this global rest frame that we can sensibly talk about a global time.

Frankly , this makes little sense to me because it seems a totally circular argument, you are using expansion to justify that all galaxies are stationary, so what is expansion then? expansion either has something to do with the galaxies proper velocities or it's something so ethereal that is useless, I know some people say expansion has nothing to do with the motion of galaxies, that is just "expanding space", but that needs to be based on the reference of motion of the galaxies to have any meaning at all. You can't have just "expanding space" because no one can say if space is expanding or not without matter as reference of that expansion.
So you basically are saying that galaxies motion is defined relative to "overall expansion", and at the same time we define expansion relative to galactic motion. Nice.
If you don't glimpse some circular reasoning here we must be talking about different universes.
But the funny thing is I don't see the need to invoke expansion, we are dealing with a possible incompatibility between the cosmological principle and the observed distribution of quasars and I haven't seen any sound argument that shows this not to be the case

No-one is trying to define a relativistically synchronized time coordinate across the universe.

That seems to be exactly what you are defining. Maybe is not what you are trying to do, but yu are doing it in practice.

What we are saying is that there is a sufficiently consistent global concept of "proper time since the big bang for a slow-moving observer", for example relative to the CMB or local galaxies.

Expansion of the universe means that the CMB or local galaxy rest frame is different at different locations, and local motions could make a little difference too, but remember that the fractional effect of speed on time rate is about (1/2) (v^2/c^2) so even 1% of the speed of light would only have an effect of 0.005% on the time rate.

Here not only you are defining a global frame but you are apparently claiming like Chalnoth that the universe is static.
When you say "sufficiently consistent global concept of proper time" even though "expansion means that the CMB is different at different locations" you are either contradicting yourself or assuming the CMB or local galaxy rest frame is the same for every location, and then you go on to add the motion of galaxies wrt this common frame is basically stationary, how do you define expansion then, what is expanding here? You are defining a purely coordinate expansion, not based on redshift that is coordinate independent and must be related to motion of galaxies to indicate expansion, but based on the spatial homogeneity assumption only. Bt this is the very assumption that we are debating wrt quasar distribution.

 

[Chalnoth]

Okay, TrickyDicky, you really need to take a step back here, because you really aren't understanding what we're saying.

When you have an expanding universe, you can describe it as having an overall, average expansion, along with local motions relative to that expansion. If you imagine that those motions are constant (i.e. no local interactions), then those motions gradually catch up to the expansion. Over time, unless you have local interactions, the expansion becomes more and more uniform.

What this means is that in the end, when you have an old universe, there ends up being hardly any motion relative to the overall expansion. The most significant motions come from the fact that there are local interactions: galaxies attract one another. But in the end, these local motions are still small compared to the overall expansion, topping out at maybe 1% of the speed of light in the largest galaxy clusters.

Because all motion different from the expansion rapidly approaches the expansion, we can define a coordinate system that is stationary with respect to the expansion. In this coordinate system, it is sensible to talk about things like global time, because this is the time coordinate that anybody will experience sitting in a solar system in any galaxy anywhere in the universe.

 

[TrickyDicky]

Okay, TrickyDicky, you really need to take a step back here, because you really aren't understanding what we're saying.

Might perfectly be the case, I'm not particularly smart. I'll try harder.

When you have an expanding universe, you can describe it as having an overall, average expansion, along with local motions relative to that expansion. If you imagine that those motions are constant (i.e. no local interactions), then those motions gradually catch up to the expansion. Over time, unless you have local interactions, the expansion becomes more and more uniform.

What this means is that in the end, when you have an old universe, there ends up being hardly any motion relative to the overall expansion. The most significant motions come from the fact that there are local interactions: galaxies attract one another. But in the end, these local motions are still small compared to the overall expansion, topping out at maybe 1% of the speed of light in the largest galaxy clusters.

Because all motion different from the expansion rapidly approaches the expansion, we can define a coordinate system that is stationary with respect to the expansion. In this coordinate system, it is sensible to talk about things like global time, because this is the time coordinate that anybody will experience sitting in a solar system in any galaxy anywhere in the universe.

But then, how exactly is expansion ascertained? I thought expansion had something to do with motion. But if motion of cosmic objects is referred to overall expansion, what do we refer overall expansion to? The CMB? And I'm still not sure if you are saying that the CMB is a global or just a local frame?, if I understand you correctly then by the overall expansion link to the CMB, it must be a global frame. I've seen some pictures of the observable universe as a sphere with us in the center and the CMB as the boundary of the sphere, with the microwave radiation reaching us isotropically from every point of the boundary, this would be compatible with the CMB as global frame and with the coordinate system defined respect to the expansion. The problem with this picture and your corrected coordinate system is that in itself it is static, and if you don't use the objects in the universe to define the expansion, how do you do it? You end up just with spatial homogeneity to justify the expansion, but you have used the slow motion of galaxies and the CMB global frame to justify that.
Cosmological redshift being coordinate-independent wouldn't help us here according to your stationary coordinate system if you separate the motion of the galaxies from the overall expansion.
I mean if anybody in any galaxy anywhere in the universe can use this global reference frame and has the same preferred choice of coordinates you defined, with no motion relative to overall expansion it could lead to think that expansion is a coordinate property and it can be dispensed with in practice.
Since I don't think you mean that , there must be something I'm misunderstanding. Maybe if you or someone answered directly any of my questions that'd help.

 

[Chalnoth]

Might perfectly be the case, I'm not particularly smart. I'll try harder.



But then, how exactly is expansion ascertained? I thought expansion had something to do with motion. But if motion of cosmic objects is referred to overall expansion, what do we refer overall expansion to? The CMB? And I'm still not sure if you are saying that the CMB is a global or just a local frame?, if I understand you correctly then by the overall expansion link to the CMB, it must be a global frame. I've seen some pictures of the observable universe as a sphere with us in the center and the CMB as the boundary of the sphere, with the microwave radiation reaching us isotropically from every point of the boundary, this would be compatible with the CMB as global frame and with the coordinate system defined respect to the expansion. The problem with this picture and your corrected coordinate system is that in itself it is static, and if you don't use the objects in the universe to define the expansion, how do you do it? You end up just with spatial homogeneity to justify the expansion, but you have used the slow motion of galaxies and the CMB global frame to justify that.
Cosmological redshift being coordinate-independent wouldn't help us here according to your stationary coordinate system if you separate the motion of the galaxies from the overall expansion.
I mean if anybody in any galaxy anywhere in the universe can use this global reference frame and has the same preferred choice of coordinates you defined, with no motion relative to overall expansion it could lead to think that expansion is a coordinate property and it can be dispensed with in practice.
Since I don't think you mean that , there must be something I'm misunderstanding. Maybe if you or someone answered directly any of my questions that'd help.

Okay, so, maybe the issue you're having here is that your argument here seems to be based upon some idea of global motion: that you can sensibly say, in some absolute sense, that we are stationary, but some far-away object is moving. Or, at the very least, that you can say that some far-away object is moving relative to us.

Neither is the case in General Relativity.

I figure you are probably aware of these facts, but you don't seem to be applying them.

The first point can be summed up with this simple statement: everything is stationary with respect to itself. Furthermore, if you have two objects separated by some distance which, according to one coordinate system are moving with respect to one another, you can come up with an alternative coordinate system where they are stationary with respect to one another. For example, if you really wanted to, you could write down some coordinates where the Sun and the Earth are both stationary. In those coordinates, anything we currently see as evidence of our motion around the Sun would still happen, but would be a result of some other physical effect in the new coordinate system. For example, the seasons would be caused not by the Earth's axis pointing in more or less the same direction but the Earth going around the Sun, instead the twisted space-time around the Sun in this new coordinate system would be applying a torque to the Earth that would cause its axis to precess. All observational effects would still work out the same (General Relativity guarantees this), but they would appear to come from different parts of the equations.

Of course, we don't make use of a coordinate system where the Earth and the Sun are both stationary, because such a coordinate system would be horribly complicated, difficult to use, and lead to all sorts of strange effects (such as the entire universe rotating around us).

But in the case of the expanding universe, it turns out that a coordinate system where everything is (nearly) stationary is incredibly useful. The redshift, instead of being due to other galaxies' motions with respect to us, instead comes about just due to the expansion of space in the interim from when the photon left to when it arrived. In this view, photons are expanded by the same effect that is causing the distances between galaxies to increase: new space is being created. So the expansion doesn't go away simply because we've used a coordinate system where everything is stationary, but the observational effect (redshifts) has a different physical explanation in the different coordinate system.

This view, where everything in the universe is nearly stationary but the space between things is increasing, is exactly the same as the view that we are stationary but everything is moving away from us, and the things further away are moving faster. The two are just different ways of looking at the exact same universe.

However, it turns out that the former view, with everything stationary and space expanding, is one heck of a lot easier to write down mathematically. And it is easier to understand some physical effects in this situation as well, such as the point that brought about this entire discussion: the fact that quasars were once common, but are now rare. In this coordinate system where everything is stationary, the time coordinate for everything is the proper time since the big bang for everything. So if, in this coordinate system, we talk about some event happening 3 billion years ago, then no matter where that event happened, we know it happened 10.7 billion years after the start of our universe from the perspective of an observer stationed at the event. And when we note that quasars were once common but are now rare, we can understand this as being due to quasar only having enough fuel to be really bright in the early universe, and that fuel later being used up.

 

[Shenstar]

The Standard Model depends on the CP (and GR) and although the CP isn't "unfalsifiable" it's also unprovable.

The quasar issue isn't the only problem for the CP. The quadrupole and octupole modes of the WMAP that seem to orient along the ecliptic plane is a problem. The Pioneer anomaly is a problem. Inflation being in tatters doesn't help.

I know of one paper that provides data regarding concentric rings at intervals radiating out... from here, home.

A bounded, finite Universe with a gravitational center would explain a lot of things, and it doesn't require an unprovable CP. But nobody is brave enough to touch it, because of the implications.

What are the implications?

The data from wmap showing that alignment on the elliptic plane has concerned me, and I never seem to get a good explanation for it.

Could you give a brief explanation of a theory that explains it or direct me to source which can preferably put it in simpler terms.

How does a universe with a gravitational centre 'work'

 

[Chalnoth]

What are the implications?

The data from wmap showing that alignment on the elliptic plane has concerned me, and I never seem to get a good explanation for it.

Could you give a brief explanation of a theory that explains it or direct me to source which can preferably put it in simpler terms.

How does a universe with a gravitational centre 'work'

Basically, when you do the statistics right, there isn't anything there.
http://arxiv.org/abs/1001.4758

One way to think about it is that the WMAP satellite gives constraints on around a million unique harmonic modes of the CMB. The fact that some tiny fraction of those modes seems, on the surface, a little bit weird, is completely expected.

 

[Shenstar]

Thanks, i did read that paper. And understood parts of it other parts were way over my head. I do understand that some things which we might consider unlikely are completely expected. Like the initials 'sh' Stephen Hawking showing up aligned etc.

But reading that paper the conclusion does state the alignment at the quad octopole are very tight and there may still be a theory to explain it, although it could just be coincidence that is expected.

I'm interested in knowing the gravitational centre theory that dougal is suggesting and the implications of such. Because like he said, maybe the implications whatever they are, are so outstretched people aren't willing to contemplate them. But we might just miss the obvious if just dismiss it as a coincidence or expected pattern/anomaly.

When will the Planck data be published? Perhaps that would confirm or negate this data

 

[Chalnoth]

Thanks, i did read that paper. And understood parts of it other parts were way over my head. I do understand that some things which we might consider unlikely are completely expected. Like the initials 'sh' Stephen Hawking showing up aligned etc.

But reading that paper the conclusion does state the alignment at the quad octopole are very tight and there may still be a theory to explain it, although it could just be coincidence that is expected.

I'm interested in knowing the gravitational centre theory that dougal is suggesting and the implications of such.

Since it's aligned with the scanning strategy of the telescope, a systematic error would not at all be unlikely.

 

[TrickyDicky]

Okay, so, maybe the issue you're having here...

Nope, that's not my issue at all AFAIK. I was the first to remark that in previous posts.
I asked some questions related to what had been discussed before, but nevermind, in some other universe of our multiverse surely you can see what I mean

 

[Chalnoth]

Nope, that's not my issue at all AFAIK. I was the first to remark that in previous posts.
I asked some questions related to what had been discussed before, but nevermind, in some other universe of our multiverse surely you can see what I mean

Well, I know you've said it, but it doesn't seem to me that you've understood the implications.

 

[Jonathan Scott]

How about reverting to the balloon model to illustrate this?

The balloon radius is the analogy of the global time. If things have moved around a little on the surface during history, then their path as the balloon expanded may have been a little different from a straight radius, so their proper time may vary a little, but not very much, as the ratio of sideways to radial motion is like the ratio of the speed to c, so it is really tiny.

What we see when we look at far away objects is what was happening when the balloon was smaller. Everyone sees the same thing at a given distance, but the properties at that distance reflect the state of the surface of the balloon at that past time.

The global time is not like a synchronized local SR flat space coordinate system. That would be like sticking a flat piece of card to the balloon, which obviously only works for a small area. When we want to discuss the evolution of distant objects, we don't mean in terms of a synchronized local SR coordinate system, but rather in terms of an approximate age in terms of their own proper time since the big bang.