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KhashayarShatti
2012-May-01, 03:30 PM
Is the universe rotating? In fact space being in rotation.
If yes then:
What happens to light from distant objects? Is there redshift?
What would the force be on distant rotating galaxies?
If no then:
Proof?

Strange
2012-May-01, 04:04 PM
Is the universe rotating? In fact space being in rotation.

If yes then:
What happens to light from distant objects? Is there redshift?

Why would it cause red shift? Rotation doesn't change the relative velocity between things.

What would the force be on distant rotating galaxies?

Pretty much zero, I assume. Given the expansion of the universe (and conservation of angular momentum) the rate of rotation (if it existed) would be very small.

profloater
2012-May-01, 05:31 PM
Is this the same question as whether a galaxy rotating (a disc with a central bulge) can explain the observed star velocities without dark matter, as recently reported?

Shaula
2012-May-01, 08:20 PM
Is this the same question as whether a galaxy rotating (a disc with a central bulge) can explain the observed star velocities without dark matter, as recently reported?
If this came from the other thread then that is not what the paper said at all.

Jens
2012-May-02, 12:07 AM
One interesting issue about this, is that IIRC, Mach suggested that rotation was in fact rotation compared to the overall mass of the universe, meaning that in his universe, by definition the universe could not be rotating, since it itself is the frame of reference from which rotation is measured. So it could be that there is an absolute frame of reference, but it could be that the mass of the universe is itself the frame of reference. I'm not sure that this question is resolved.

profloater
2012-May-02, 10:03 AM
If this came from the other thread then that is not what the paper said at all. Oh I thought it did: I copied this from that:

Galactic Rotation... no need for dark matter.
Galactic Rotation Described with Bulge+Disk Gravitational Models
C. F. Gallo, James Q. Feng
(Submitted on 20 Apr 2008)

http://search.arxiv.org:8081/details...df/0804.3203v1

KhashayarShatti
2012-May-02, 01:53 PM
By a simple observational experiment, i think one could find out whether the universe(space and matter) is rotating or not. Galactic alignment of the solar system could be the best proof of this if and only if it turns out to be compatible and in agreement with the tilting of other galaxies. You see if 3 degrees of freedom of rotation of a few galaxies are observed then by a single rotation of the universe all the galaxies will be affected and rotate in accordance with the formula T=I *w1 x w2 , the moment that causes a third rotation. In this case the axis of rotation and the poles of the universe could also be detected, yes?

profloater
2012-May-02, 02:40 PM
However simple it might take a long time!:) You might also look for relative movement (parallax) of near and far galaxies.

Strange
2012-May-02, 02:56 PM
By a simple observational experiment, i think one could find out whether the universe(space and matter) is rotating or not. Galactic alignment of the solar system could be the best proof of this if and only if it turns out to be compatible and in agreement with the tilting of other galaxies. You see if 3 degrees of freedom of rotation of a few galaxies are observed then by a single rotation of the universe all the galaxies will be affected and rotate in accordance with the formula T=I *w1 x w2 , the moment that causes a third rotation. In this case the axis of rotation and the poles of the universe could also be detected, yes?

I think (not sure) that one piece of evidence used to argue that there might be some overall angular momentum is the fact we tend to see more galaxies rotating one way than the other. It is not clear that this is not sampling bias, though. I think there is another thread on this...

Shaula
2012-May-02, 04:56 PM
Oh I thought it did: I copied this from that:

Galactic Rotation... no need for dark matter.
Galactic Rotation Described with Bulge+Disk Gravitational Models
It said that there was less need for dark matter in the disk of the galaxy while maintaining a halo of it. I did point that out in the thread it first came up in - a complete reading of the paper showed that they were arguing for an adjustment of the amount of baryonic and non-baryonic dark matter in the galactic disk that was still within LCDM bounds.

antoniseb
2012-May-02, 05:55 PM
We often get people asking if the universe is rotating (after all, they usually say, everything else is). If you think for a few minutes, there are a few questions that ought to come up clarifying what you are asking:
- Would that imply there is a center of rotation? If so where is it?
- If the actual universe is much larger than the visible universe wouldn't the likely position of the center of rotation be outside the visible universe, and if so, would that rotation be detectable?
- If the radius of the entire (more than just visible) universe is a trillion light years (plausible), what is the maximum rate of rotation we should be seeing?
- Is angular momentum conserved on universal scale? If so, was it rotating when inflation ended? How fast? What would the the angular speed now?
- If it is rotating, is it only rotating in our three spatial dimensions?

To me, this all kind of implies that if the Universe is rotating, it is not rotating fast enough to be an important issue.

utesfan100
2012-May-02, 06:31 PM
We often get people asking if the universe is rotating (after all, they usually say, everything else is). If you think for a few minutes, there are a few questions that ought to come up clarifying what you are asking:

It seems like the best definition of a universal rotation would be a expressed as a space-like angular velocity vector.

Q: Would that imply there is a center of rotation? If so where is it? A: No. The origin of any frame would be the center of rotation of that frame.
Q: If the actual universe is much larger than the visible universe wouldn't the likely position of the center of rotation be outside the visible universe, and if so, would that rotation be detectable? A: This question presumed the first question is correct.
Q: If the radius of the entire (more than just visible) universe is a trillion light years (plausible), what is the maximum rate of rotation we should be seeing? A: The rotation is a universal constant.
Q: Is angular momentum conserved on universal scale? If so, was it rotating when inflation ended? How fast? What would the the angular speed now? A: This depends on whether our angular velocity is truely absolute, or merely an approximation in our experimentally explorable volume.
Q: If it is rotating, is it only rotating in our three spatial dimensions? A: Yes, though it is likely to be purely spatial only in the CMBR frame.

To me, this all kind of implies that if the Universe is rotating, it is not rotating fast enough to be an important issue.
This view of a definition of rotation, however, would be difficult to distinguish from a defect in the ICRF. One would have to show that relative to the ICRF there is an apparent Coriolis force. This could appear, for example, as object at the same radius but opposite direction having different orbital period.

I believe that such an effect is tightly constrained by observation, thus the universe's rotation is not distinguishable from 0.

KhashayarShatti
2012-May-03, 08:44 AM
....
- If the actual universe is much larger than the visible universe wouldn't the likely position of the center of rotation be outside the visible universe, and if so, would that rotation be detectable?
- If the radius of the entire (more than just visible) universe is a trillion light years (plausible), what is the maximum rate of rotation we should be seeing?
.....
If sophisticated detecting equipment exist to differentiate the difference in rotation between one side of visible universe and the other side,then could this technique identify, by extrapolation, the size of the invisible universe and guess the position of the centre?
As a theoretical example, lets imagine the universe is doughnut(torus) shaped. In this case one could imagine one visible side to be at R1 radius and the other visible side to be at R1+27 billion light years of age. Now the only parameter we could measure is the difference between the rotation of these two sides. Is it enough data to detect the position of the centre of this invisible universe or more data are required?

KhashayarShatti
2012-May-04, 09:34 AM
I believe that such an effect is tightly constrained by observation, thus the universe's rotation is not distinguishable from 0.
In order to minimize observational errors, perhaps detecting the difference between 3rd axis rotation of nearby galaxies for a longer period could help. Although rotations are said to be slow but sizes of galaxies(100000 light years across) are very large.

Ivan Viehoff
2012-May-08, 10:23 AM
By a simple observational experiment, i think one could find out whether the universe(space and matter) is rotating or not. Galactic alignment of the solar system could be the best proof of this if and only if it turns out to be compatible and in agreement with the tilting of other galaxies. You see if 3 degrees of freedom of rotation of a few galaxies are observed then by a single rotation of the universe all the galaxies will be affected and rotate in accordance with the formula T=I *w1 x w2 , the moment that causes a third rotation. In this case the axis of rotation and the poles of the universe could also be detected, yes?
No.

Did you read what Jens wrote? To repeat it, if space itself was rotating, then since it is our reference frame we would not notice if everything else was rotating along with it. Relative to the reference frame, the items within the space of the universe would not have any net angular momentum. We can only notice if the contents of the universe are rotating relative to the space they sit in.

Hence it is a meaningless question to ask if the universe itself, ie, space and matter all together, is rotating. You can't sit outside space and observe whether it is rotating relative to some larger frame.

Also, observationally, the universe is anisotropic. So it would not appear that the matter of the universe is collectively rotating relative to space either.

Aethelwulf
2012-May-08, 12:31 PM
Is the universe rotating? In fact space being in rotation.
If yes then:
What happens to light from distant objects? Is there redshift?
What would the force be on distant rotating galaxies?
If no then:
Proof?

It is believed by some scientists that there is a specific handedness with the rotation of galaxies and they attribute this phenomenon possibly due to the universe spinning very early on in its history.

Ivan Viehoff
2012-May-08, 02:00 PM
It is believed by some scientists that there is a specific handedness with the rotation of galaxies and they attribute this phenomenon possibly due to the universe spinning very early on in its history.
I suspect when you say "universe" here, you mean "the matter in the universe". OP is asking whether space itself, together with the matter in it, is spinning.

Aethelwulf
2012-May-08, 02:02 PM
I suspect when you say "universe" here, you mean "the matter in the universe". OP is asking whether space itself, together with the matter in it, is spinning.

Some Cosmologists have investigated whether it was possible that the universe was spinning causing the handedness of spinning galaxies. I meant what I said. In their study, the universe would indeed be spinning very early on in the universe giving rise to the specific directionality of spin among galaxies.

KhashayarShatti
2012-May-09, 03:58 PM
..... You can't sit outside space and observe whether it is rotating relative to some larger frame.

Right.You can't sit outside space and observe whether it is rotating relative to some larger frame. But this argument is not scientific. Scientifically no one can be sure that nothing exists outside the universe. The clue is within the behaviour of galaxies. Lots of intelligence exists that haven't been decoded about the rotation of galaxies. But there seems to be some clue. This space and this matter match one another. From point of view of material engineering, If one could make another proportion, perhaps another space with another type of matter could exist(for example:BH). To some extent the behaviour of the universe appears to have some shear force similar to the stir of a cup of coffee with milk. You see magnetars are some indication of the existence of strong magnetic field that can power early rotation of the plasma(charge particles) state of matter as the universe expanded.But the shear force can affect both space and matter at the same time. In general, whatever the reality, there might be some harmony affecting all galaxies in proportion which may be a good clue to determine if the universe(matter) with its container(space) has a centre. I think if it is proved that the universe has a centre then a measure of some sort of size of the universe could be realized.

Van Rijn
2012-May-10, 12:25 AM
It is believed by some scientists that there is a specific handedness with the rotation of galaxies and they attribute this phenomenon possibly due to the universe spinning very early on in its history.

Through Galaxy Zoo a lot of galaxies were examined, and they didn't find evidence for universal preferred rotation. I think this article gets into that:

http://arxiv.org/abs/0803.3247

Jens
2012-May-10, 02:07 AM
- Would that imply there is a center of rotation? If so where is it?

This might be complicating the issue, but I've wondered, what if the universe were actually rotating in a further dimension? As an analogy, we could take the surface of a sphere rotating in three dimensions. In that case there are two centers, right? So what would happen if the universe were actually a three-dimensional space rotating in a four-dimensional space?

KhashayarShatti
2012-May-10, 01:07 PM
If time and space are said to be highly correlated, then is it possible to refer to it as "Absolute Space" instead of 4D space? If we reduce time, we can say it all becomes space with no time. So could there be a kind of absolute space with no time, in which this universe exists?I think rotation of the universe could be a clue.At least it could give a possibility whether you call it 4th dimension or absolute space or whatever mainstream perhaps refers to it as 11 dimension or parallel universes, etc., perhaps if it turns out that all galaxies have a common 3rd rotation in proportion, with no reason except an external effect.

Ivan Viehoff
2012-May-10, 01:28 PM
Some Cosmologists have investigated whether it was possible that the universe was spinning causing the handedness of spinning galaxies. I meant what I said. In their study, the universe would indeed be spinning very early on in the universe giving rise to the specific directionality of spin among galaxies.
But, for the reason Jens originally gave, and which I repeated in my other posts, this only makes sense if in fact when they say "the universe" they mean "what lies within universe, not the space itself". If the space of the universe was rotating and along with it the matter, we would not perceive the rotation and it would not result in any preferential handedness in the spinning of galaxies perceived within the space of the universe.

Ivan Viehoff
2012-May-10, 01:30 PM
Right.You can't sit outside space and observe whether it is rotating relative to some larger frame. But this argument is not scientific. Scientifically no one can be sure that nothing exists outside the universe..
Perfect. You understand me entirely, it seems, until

The clue is within the behaviour of galaxies.

NEOWatcher
2012-May-10, 01:53 PM
If we reduce time, we can say it all becomes space with no time.
No, that's not how dimensions work.
If I reduce X in a 2d system, I am still somewhere in 2d space. X does not go away because we can still move in X.

KhashayarShatti
2012-May-10, 02:09 PM
But, for the reason Jens originally gave, and which I repeated in my other posts, this only makes sense if in fact when they say "the universe" they mean "what lies within universe, not the space itself". If the space of the universe was rotating and along with it the matter, we would not perceive the rotation and ......

From an engineering point of view, you know that older technology rate gyroscopes have a rotating disc and a frame to hold it. Take two gyroscopes and rotate their frame about a common centre twice as far away from one of them. Now If I refer to galaxies as gyroscope discs and the space as the frame that holds these discs, then if and only if the frame is torqued, the discs would sense a common third rotation, yes? The only difference is that the frame of the galaxies is not seen and not sensed perhaps due to the fact that gravity is unidirectional. The only thing that IS sensed and could be observed is the difference in 3rd rotation of galaxies.

profloater
2012-May-10, 02:24 PM
In that analogy what is the frame constraining the two galaxy gyroscopes together? Indeed what is the frame holding the stars of the galaxy? The analogy is more like a gas or fluid gyro as was used in fluid logic gates but they do not behave like a rigid rotor in gimbals. I gather that two galaxies would be treated like two point masses for cosmology, so their spin hardly has any way to communicate one to the other. I guess they represent the local net spin angular momentum of the particles from which they coallesced.

Aethelwulf
2012-May-10, 02:50 PM
But, for the reason Jens originally gave, and which I repeated in my other posts, this only makes sense if in fact when they say "the universe" they mean "what lies within universe, not the space itself". If the space of the universe was rotating and along with it the matter, we would not perceive the rotation and it would not result in any preferential handedness in the spinning of galaxies perceived within the space of the universe.

The biggest problem of a rotating universe is the question of what the universe is rotating relative to?

It would require a boundary.

HenrikOlsen
2012-May-10, 04:46 PM
Not really.

Rotation is an absolute (as opposed to relative) property, measurable1 without outside references.

1) There's a practical limit to how slow rotations are measurable, but that doesn't disprove that rotation doesn't need anything to rotate relative to.

Swift
2012-May-10, 05:11 PM
From an engineering point of view, you know that older technology rate gyroscopes have a rotating disc and a frame to hold it. Take two gyroscopes and rotate their frame about a common centre twice as far away from one of them. Now If I refer to galaxies as gyroscope discs and the space as the frame that holds these discs, then if and only if the frame is torqued, the discs would sense a common third rotation, yes? The only difference is that the frame of the galaxies is not seen and not sensed perhaps due to the fact that gravity is unidirectional. The only thing that IS sensed and could be observed is the difference in 3rd rotation of galaxies.
What makes you think the analogy to a mechanical gyroscope is a good model of a rotating galaxy or a rotating universe?

Aethelwulf
2012-May-10, 05:19 PM
Where did you get that from?

I've heard conflicting arguments. If you could direct me in the right way? Even if that a boundary condition is not required, I have also heard that if the universe rotated it would actually cause a high scale Anisotropy.

Aethelwulf
2012-May-10, 05:19 PM
To Henrik^

HenrikOlsen
2012-May-10, 06:14 PM
Where did you get that from?

I've heard conflicting arguments. If you could direct me in the right way? Even if that a boundary condition is not required, I have also heard that if the universe rotated it would actually cause a high scale Anisotropy.
A rotating frame gives rise to Coriolis forces which are locally measurable (see caveat about measuring very small forces in practice) without reference to anything outside the frame.

Aethelwulf
2012-May-10, 07:34 PM
A rotating frame gives rise to Coriolis forces which are locally measurable (see caveat about measuring very small forces in practice) without reference to anything outside the frame.

The Coriolis force is

\frac{2\vec{\omega}c}{\sqrt{G}} = F

This is also called the gravimagnetic field. Things rotate independent of the rotation of the universe, producing their own gravimagnetic fields. The gravimagnetic field however of a gyroscope is an experience of a type of torsion of the gravitational field as a frame-dragging effect.

In other words, your argument does not make sense in my mind. The rotation of the universe might give rise to the angular momentum of star systems in our universe, but the gravimagnetic forces would be local to the mass proportional to the celestial objects we see, it would not give a direct evidence this is caused at all from some universal rotation. But perhaps, the important point is as I mentioned: the gravimagnetic forces are frame-dependent. This is why it is called ''frame-dragging''.

ref: Motz, On the Quantization of Mass (for the gravimagnetic field as the Coriolis force.)

KhashayarShatti
2012-May-10, 07:35 PM
What makes you think the analogy to a mechanical gyroscope is a good model of a rotating galaxy or a rotating universe?
An image of Galactic alignment in which the plane of the solar system was shown as an ellipse with respect to the milkey way. I tried to find it but I couldn't. In that photo it was quite clear that the plane of the solar system is going to become orthogonal to the plane of the galaxy at an inclination of almost 60 degrees. Sometimes it strikes every engineers mind familiar with gyros to think of a gyroscopic effect.

Swift
2012-May-10, 07:55 PM
An image of Galactic alignment in which the plane of the solar system was shown as an ellipse with respect to the milkey way. I tried to find it but I couldn't. In that photo it was quite clear that the plane of the solar system is going to become orthogonal to the plane of the galaxy at an inclination of almost 60 degrees. Sometimes it strikes every engineers mind familiar with gyros to think of a gyroscopic effect.
I won't argue whether a galaxy looks like a gyroscope or not (I don't particularly think it does). But even if it does, it doesn't mean that a gyroscope is a good model of a galaxy.