Cat, I have answered that as best I can. You seem to ignore my answer, which is that a spinning frame of reference will produce internal accelerations that can be detected if they are strong enough, and could be misinterpreted as forces, rather than "pseudo" forces such as the Coriolis Force is said to be on a spinning Earth.This does not answer my post #48.
Cat
The link I provided seems to be able to deal with my view of "spin" in the universe and has tested for it, and not found it.
What more are you looking for in the way of an answer? We just do not agree that "spin" cannot exist of be detected in a closed system (e.g., the universe) without some external reference point. I think it can, and have explained why I think that. If you don't agree with my position, what do you think is wrong with it?
Catastrophe
"Science begets knowledge, opinion ignorance.
Unc, I hope that I may be forgiven for repeating #48, since it is "round the corner" and is, in my opinion a complete answer to the whole question:
The underlines are intended to answer 1 . . . 2 . . . 3. EO.
I am sorry to disagree, but I do totally disagree that the Universe can spin, having no external marker. Secondly, if no "centrifugal" can be measured, then science must say that they do not exist (in an objective world), zero = NO, EO. "and not found" . . . "If yu cann't measure it, it ain't thur".
That IS my position, and I think it answers your comment in its entirety. I accept your right to believe what you like, but I do totally disagree with you in this matter, and I do believe that I have answered your point fully. No hard feelings, of course
Cat
My emphasis.
The underlines are intended to answer 1 . . . 2 . . . 3. EO.
I am sorry to disagree, but I do totally disagree that the Universe can spin, having no external marker. Secondly, if no "centrifugal" can be measured, then science must say that they do not exist (in an objective world), zero = NO, EO. "and not found" . . . "If yu cann't measure it, it ain't thur".
That IS my position, and I think it answers your comment in its entirety. I accept your right to believe what you like, but I do totally disagree with you in this matter, and I do believe that I have answered your point fully. No hard feelings, of course
Cat
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I think the difference is that you seem to rely on the measurement that says the universe does not have detectable spin to somehow imply that the universe could not have spin on a theoretical basis, thus making it logically unnecessary to even test for it.
My position is that, in theory as far as we currently understand things, a universe might have "spin" because it is not precluded by our physical understanding of things. That is different than thinking it is precluded.
So, that is the only point of difference - we agree that it does not seem to have spin, based on the test in the link that I provided.
My position is that, in theory as far as we currently understand things, a universe might have "spin" because it is not precluded by our physical understanding of things. That is different than thinking it is precluded.
So, that is the only point of difference - we agree that it does not seem to have spin, based on the test in the link that I provided.
Catastrophe
"Science begets knowledge, opinion ignorance.
No, Unc, I am definitely saying that spin is relative to something. Something is spinning around an axis and can only be measured against an external marker. To say that the Universe is spinning is like saying that a stationary object is going at 80 mph. Or that the colourless object is green.
There is the additional problem that spin, sadly, is ambiguous. As in, the Earth is spinning around its axis - so we have day and night, AND the Earth is spinning around the Sun - so we have summer and winter. Are you also saying that the Universe can spin around something? If not, why does it apply to the Earth and not to the Universe?
Coming back to the first point - day and night raises an interesting point. It requires the Sun to provide day and night - the Sun is the marker. What marker shows that the Universe is spinning? If there is no marker, there is no spin.
This whole thing is a question of semantics. Give a dog a bad name and hang it. Do you have this old saying in US? Call a colourless object green, and it looks green. Say that the Universe spins, and it has an invisible unproven marker. The only "proof" of spin is that someone says it spins. All dogs are yellow, all cats are green, all elephants are one inch tall, all planets have moons, All universes spin. Take your pick.
Cat
P.S. Spin must be quantified relative to something external. But, by definition, the Universe is all there is. So any "external" marker must be part of the Universe. But the Universe cannot spin relative to itself. So you must postulate another "external" marker, but this "external" marker must be part of the Universe . . . . . . . . . ad infinitum. There is no spin without an external marker. But any external marker must be part of the Universe . . . . . . unless all colourless cats are green.
There is the additional problem that spin, sadly, is ambiguous. As in, the Earth is spinning around its axis - so we have day and night, AND the Earth is spinning around the Sun - so we have summer and winter. Are you also saying that the Universe can spin around something? If not, why does it apply to the Earth and not to the Universe?
Coming back to the first point - day and night raises an interesting point. It requires the Sun to provide day and night - the Sun is the marker. What marker shows that the Universe is spinning? If there is no marker, there is no spin.
This whole thing is a question of semantics. Give a dog a bad name and hang it. Do you have this old saying in US? Call a colourless object green, and it looks green. Say that the Universe spins, and it has an invisible unproven marker. The only "proof" of spin is that someone says it spins. All dogs are yellow, all cats are green, all elephants are one inch tall, all planets have moons, All universes spin. Take your pick.
Cat
P.S. Spin must be quantified relative to something external. But, by definition, the Universe is all there is. So any "external" marker must be part of the Universe. But the Universe cannot spin relative to itself. So you must postulate another "external" marker, but this "external" marker must be part of the Universe . . . . . . . . . ad infinitum. There is no spin without an external marker. But any external marker must be part of the Universe . . . . . . unless all colourless cats are green.
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Cat, I do understand that you do not conceive of "spin" without having an external marker to serve as a "fixed" point.
But, you keep expressing that position without discussing what is wrong with my position that "spin" can be measured internally by noting deviations from the known physics of an inertial frame of reference, which a spinning frame of reference is not.
Unless you can convince me that an observer in a spinning frame of reference cannot distinguish that frame from an inertial frame unless he has an external marker in an inertial frame , then we are just talking around the point of disagreement instead of addressing it directly.
And remember, I am agreeing with the linked article that spin could have been detected if it was present, but it appears to not be present. So, I am not insisting that there must be some spin that we are not detecting.
The only difference in our positions is that you seem to think that spin cannot exist in the universe, and I don't see any physics that would preclude it, nor physics that would make it impossible to detect. Hard to detect, maybe. Possible to misinterpret, maybe.
But, you keep expressing that position without discussing what is wrong with my position that "spin" can be measured internally by noting deviations from the known physics of an inertial frame of reference, which a spinning frame of reference is not.
Unless you can convince me that an observer in a spinning frame of reference cannot distinguish that frame from an inertial frame unless he has an external marker in an inertial frame , then we are just talking around the point of disagreement instead of addressing it directly.
And remember, I am agreeing with the linked article that spin could have been detected if it was present, but it appears to not be present. So, I am not insisting that there must be some spin that we are not detecting.
The only difference in our positions is that you seem to think that spin cannot exist in the universe, and I don't see any physics that would preclude it, nor physics that would make it impossible to detect. Hard to detect, maybe. Possible to misinterpret, maybe.
Catastrophe
"Science begets knowledge, opinion ignorance.
Unc, can you please clarify what you mean by spin relative to an external frame of reference can be measured internally?
Anything in the Universe can spin relative to something else, and probably does. I see my answers to your assertion about 'internal measurement' as
and I don't think that you are answering my points.
Either we find some common ground, or we just "call it a draw" and depart in friendship. As you know, I have great respect for you, and a little disagreement on a question of semantics is not going to change that.
Frankly, I don't understand what you are talking about. Could you please, maybe look at my point of vies which is, at least, stated in simple form?
You state
This is absolutely 100% totally not the case. See above
What I am saying is that the Universe, in toto, cannot spin because there is nothing by which that spin can be measured. No day and night without the Sun.
Can you please just state your position on that?
Cat
Only an internal test for deviation from an inertial frame of reference can be used to determine if the universe is spinning. If one looks at a supposed external reference frame then one must assume the external reference frame is not the one that is spinning.
If you are on a spinning ride at the carnival with your eyes closed, it is easy to determine that you are spinning as your arms fly out and your inner ear fluids slosh around. There is no need for an external reference.
Any spin that the universe has could be determined by looking at the spins of galaxies to see if there is an excess of right handed or left handed spins. Here is a paper from 2011 that claims the universe is spinning..
Detection of a dipole in the handedness of spiral galaxies with redshifts z∼0.04 - ScienceDirect
If you are on a spinning ride at the carnival with your eyes closed, it is easy to determine that you are spinning as your arms fly out and your inner ear fluids slosh around. There is no need for an external reference.
Any spin that the universe has could be determined by looking at the spins of galaxies to see if there is an excess of right handed or left handed spins. Here is a paper from 2011 that claims the universe is spinning..
Detection of a dipole in the handedness of spiral galaxies with redshifts z∼0.04 - ScienceDirect
Catastrophe
"Science begets knowledge, opinion ignorance.
Then the problem is solved. You agree with me that we both recognise that spin exists within the Universe - there being a multitude of examples including stars and planets and moons spinning around their own axes.
You do not dispute that the Universe itself cannot be measured as spinning relative to anything. Ergo, the Universe itself does not spin.
Cat
Cat, I suggest we just call this a "draw" as you suggested. Your restatements of my position do not accurately reflect my actual position. I do dispute "that the Universe itself cannot be measured as spinning relative to anything. Ergo, the Universe itself does not spin." And, both Bill and I have stated how that can be done.
And, where you asked (again) "Unc, can you please clarify what you mean by spin relative to an external frame of reference can be measured internally?", you are bypassing the whole concept of an inertial frame of reference.
We will not ever be able to resolve this so long as you can only envision a frame of reference to be external to a spinning frame of reference. If you want to continue, you will need to discuss an internal frame of reference where things in motion do not change direction unless acted upon by a force.
What spurred me to ask this question in the first place is that theorists keep postulating forces from unknown "energies" working by unknown physics to explain astronomical observations and theoretical traps (like how the whole universe could have expanded out of a black hole that the theory puts it into.) That logically raises the question about whether those foces (at least the observed ones) could be misinterpretations of phenomena that occur because we assume that we are relating them to an inertial frame of reference when, actually, we are misinterpreting an accelerating frame of reference as inertial.
Bill has now added another link to the conversation, which also looked for signs that the universe has spin. And, it came to the opposite conclusion from the first paper that you linked. So, I still think this is a relevant question that should not be avoided simply on the basis of word definitions.
With even "the best" theories claiming that we do not properly understand 95% of what we can observe, there should be plenty of room for questioning how we interpret what we are observing.
And, where you asked (again) "Unc, can you please clarify what you mean by spin relative to an external frame of reference can be measured internally?", you are bypassing the whole concept of an inertial frame of reference.
We will not ever be able to resolve this so long as you can only envision a frame of reference to be external to a spinning frame of reference. If you want to continue, you will need to discuss an internal frame of reference where things in motion do not change direction unless acted upon by a force.
What spurred me to ask this question in the first place is that theorists keep postulating forces from unknown "energies" working by unknown physics to explain astronomical observations and theoretical traps (like how the whole universe could have expanded out of a black hole that the theory puts it into.) That logically raises the question about whether those foces (at least the observed ones) could be misinterpretations of phenomena that occur because we assume that we are relating them to an inertial frame of reference when, actually, we are misinterpreting an accelerating frame of reference as inertial.
Bill has now added another link to the conversation, which also looked for signs that the universe has spin. And, it came to the opposite conclusion from the first paper that you linked. So, I still think this is a relevant question that should not be avoided simply on the basis of word definitions.
With even "the best" theories claiming that we do not properly understand 95% of what we can observe, there should be plenty of room for questioning how we interpret what we are observing.
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Catastrophe
"Science begets knowledge, opinion ignorance.
Bill,
Cat
If you are arguing that the whole is not greater than the part, then I have no response.
Cat
Catastrophe
"Science begets knowledge, opinion ignorance.
"If you are arguing that the whole is not greater than the part, then I have no response." - Catastrophe
I don't know what that means.
I am arguing that the rotation of a system can be determined only from within.
I don't know what that means.
I am arguing that the rotation of a system can be determined only from within.
IG2007
"Don't criticize what you can't understand..."
I think I am a bit late, but well, I will still enter the fray because this is an interesting thread
The following is my opinion on this topic:
Firstly, we need to discuss if we are talking about The Universe or A universe.
If we are talking about The Universe, then well, it is not possible to measure the spin of our Universe without an outside reference and as The Universe is defined as all that exists, there cannot be any outside reference. The fact that our Earth rotates around its axis was only proven by the movement of the stars and the oblateness of the poles, later corroborated by satellites (another outside reference, mind you). One might argue that, if the Universe is a sphere and it spins, then, its poles might be oblate too and therefore, there is a possibility of proving that it is spinning. But well, The Universe, by its very definition, cannot have a boundary, as there is nothing outside it.
Now well, if we are to establish a conversation about the spin of A universe, however, we must establish that there are other universes, which, if you are a student of the quantum world, might not surprise you. But, well, as it is not possible to observe anything outside the realm of our universe, we cannot observe other universe, and hence we cannot state scientifically that there are other universes - it can only remain in the realm of hypotheses and possibilities.
I hope my viewpoint has satisfied most, if not all of whom reading this, as it is hard to please all.
I dunno, I haven't ever been thrown out of the window with wind speeds of more than thousands of kilometres per hour making me head right into the vacuum.
The following is my opinion on this topic:
Firstly, we need to discuss if we are talking about The Universe or A universe.
If we are talking about The Universe, then well, it is not possible to measure the spin of our Universe without an outside reference and as The Universe is defined as all that exists, there cannot be any outside reference. The fact that our Earth rotates around its axis was only proven by the movement of the stars and the oblateness of the poles, later corroborated by satellites (another outside reference, mind you). One might argue that, if the Universe is a sphere and it spins, then, its poles might be oblate too and therefore, there is a possibility of proving that it is spinning. But well, The Universe, by its very definition, cannot have a boundary, as there is nothing outside it.
Now well, if we are to establish a conversation about the spin of A universe, however, we must establish that there are other universes, which, if you are a student of the quantum world, might not surprise you. But, well, as it is not possible to observe anything outside the realm of our universe, we cannot observe other universe, and hence we cannot state scientifically that there are other universes - it can only remain in the realm of hypotheses and possibilities.
I hope my viewpoint has satisfied most, if not all of whom reading this, as it is hard to please all.
While this is a continuing thread, I just want to still bring in the perspective from #21 (my sincere apologies for any repeat)
Every object that we know in the universe (as of date) has motion, they spin on their axis and as well revolve around larger objects in certain orbits. Even the Superclusters may have some movement though we don't know for sure yet Superclusters-Motion.
When everything in the our frames of reference is moving, earth's rotation, revolution around sun, Sun moving around our galaxy Milkyway, and possibly Milkyway itself moving inside our Supercluster Laniakea. And while all these are moving they are bending and dragging the Space Time fabric also along with it. Our point of observation of this Visible Universe which we don't know for sure where we are in this universe (say if it is spinning) then our sun/galaxy/supercluster is not necessarily are at the center of the Universe, we could be anywhere far flung edge of a spinning universe and while we observe from earth with so many relative motions in action, how can we so certain that the stars are not actually receding from each other in an expanding universe but actually spinning away because the frame in which we are observing we are only able to observe it in such a way!!!
Every object that we know in the universe (as of date) has motion, they spin on their axis and as well revolve around larger objects in certain orbits. Even the Superclusters may have some movement though we don't know for sure yet Superclusters-Motion.
When everything in the our frames of reference is moving, earth's rotation, revolution around sun, Sun moving around our galaxy Milkyway, and possibly Milkyway itself moving inside our Supercluster Laniakea. And while all these are moving they are bending and dragging the Space Time fabric also along with it. Our point of observation of this Visible Universe which we don't know for sure where we are in this universe (say if it is spinning) then our sun/galaxy/supercluster is not necessarily are at the center of the Universe, we could be anywhere far flung edge of a spinning universe and while we observe from earth with so many relative motions in action, how can we so certain that the stars are not actually receding from each other in an expanding universe but actually spinning away because the frame in which we are observing we are only able to observe it in such a way!!!
"... it is not possible to measure the spin of our Universe without an outside reference." IG2007
I don't believe this is true, in fact I am pretty sure the opposite is true. If you saw an outside reference moving sideways how would you know if it were you moving or the reference moving? There would be no way to tell.
Only a measurement within our frame of reference can determine if it is rotating. This is done by extablishing a flat level surface and stringing a straight line upon it. A marble is then rolled along the line. If the marble deviates from the straight line then the frame of reference is rotating.
I don't believe this is true, in fact I am pretty sure the opposite is true. If you saw an outside reference moving sideways how would you know if it were you moving or the reference moving? There would be no way to tell.
Only a measurement within our frame of reference can determine if it is rotating. This is done by extablishing a flat level surface and stringing a straight line upon it. A marble is then rolled along the line. If the marble deviates from the straight line then the frame of reference is rotating.
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IG2007
"Don't criticize what you can't understand..."
Firstly, I do not understand how objects spinning in a system make it plausible that the entire system is rotating. Secondly, I do not think the revolutions of the planets and stars have anything to do with the rotations. The Earth does not rotate because it revolves around the sun, it is because of the way it was formed, by continuous collisions of massive bodies.
Well, do not blame me if the marble is spinning along the universe too, then there would probably be no deviation.
Moreover, how can we see an outside reference moving sideways if there is no outside reference to observe? We cannot argue for the motion of a body without looking from the perspective of another body, motion is relative.
Yes it is collisions or as well as massive bodies bending and dragging space along when they move. Like satellites revolving around planets, planets revolving around the sun, Stars in galaxies revolving around a center which is possibly a giant black hole thus we can say galaxies are also spinning. Now we don't know yet if these galaxies while they are spinning are as well revolving within the superclusters they belong!!! And if so then, are these supercluster spinning and like this so many questions not answered yet.
Also, we know from observation that stars are moving further and further away (expanding Universe), hence Universe is also in motion. This we are able to tell by observing from within our frame of reference in our universe.
Hence the question is what makes us so confident that Universe (as we know) is not spinning thus creating an effect of stars receding away from us (from the point of our observation on earth). Maybe it is an expanding universe or Spinning universe or an expanding universe that is as well as spinning.
Now if it is spinning then a very valid question by @Cat is about the definition of Universe (if all that we know spins then what is it spinning inside hence the theoretical concept of a super universe where you have multiverses and ours being one of the MCU-616 verse??
. Thus the dilemma of real Physics versus Metaphysics leading to more debates in the above forums. The latter is thought provoking, has helped science but as well is hijacked by fiction writers to a billion dollars franchise.
There is deviation from a straight line in any rotating frame of reference. This is what makes storm systems rotate on Earth. Commonly known as the Coriolis force.
And, yes, we cannot see our universe rotating against an outside reference simply because there is no outside reference. Even if there was, we would have no way of knowing if the outside reference itself was rotating.
There really is no "metaphysics" in the question. I probably could reframe the question as:
Is the universe we are observing consistent with a inertial frame of reference?
That should get us past the idea of outside-the-universe reference points, so we can talk about the actual internal physics.
But, it also brings in the concept of other accelerations besides rotational acceleration. And we are already hearing that the universe is accelerating its expansion.
So, the question I had in mind is whether we could be misinterpreting one type of acceleration as a different type of acceleration. We can't explain the cause of the one we think we see with anything that we actually understand.
Is the universe we are observing consistent with a inertial frame of reference?
That should get us past the idea of outside-the-universe reference points, so we can talk about the actual internal physics.
But, it also brings in the concept of other accelerations besides rotational acceleration. And we are already hearing that the universe is accelerating its expansion.
So, the question I had in mind is whether we could be misinterpreting one type of acceleration as a different type of acceleration. We can't explain the cause of the one we think we see with anything that we actually understand.
There is a difference between the possible rotation of the universe and the expansion. The rotation is seen as a tangential velocity at far distances. The expansion is seen as a radial velocity at far distances.
Unfortunately, I don't think there is any way to detect movement across our field of view other than taking two images many years apart by a camera that is not rotating. This is not possible in a practical sense.
The best way I have seen is to simply average out the rotation vectors of many distant galaxies. Each galaxy forms by aggregating the local moment of inertia, just like storms on Earth. This has been done and shown a slight amount of spin. See post #58.
Unfortunately, I don't think there is any way to detect movement across our field of view other than taking two images many years apart by a camera that is not rotating. This is not possible in a practical sense.
The best way I have seen is to simply average out the rotation vectors of many distant galaxies. Each galaxy forms by aggregating the local moment of inertia, just like storms on Earth. This has been done and shown a slight amount of spin. See post #58.
I agree that the two directions of motion are different.
But, if a rotating frame of reference is mistakenly perceived as an inertial frame of reference, then what appears to be radial motion is actually straight line motion in an inertial frame with the rotating frame's apparent radial change in distance being perceived as due to a mysterious force.
The link Cat posted in reply #24 uses the "Bianchi cosmologies" which are the equations resulting from not assuming that the universe is isotropic when solving the field equations in General Relativity Theory. The authors claim that their work is the first to "consider all degrees of freedom in these solutions to conduct a general test of isotropy using cosmic microwave background temperature and polarization data from Planck." Their result is that it looks highly unlikely that the universe has "spin".
Not being able to check their assumptions, math or data myself, I have to take their word for it as the best effort to date to address my question. That does not mean that I am positive that no future study could come to a different conclusion when more is known or errors in math or modeling are uncovered. But, it is a reasonable result that comes from a reasonable effort to address the question. So, at this point, I am accepting the following:
1. It is a reasonable question that can be addressed.
2. It has been addressed in a very comprehensive (and complex) manner in the linked paper.
3. The conclusion is that there is high probability that the universe has no intrinsic spin (nor anisotropy in direction).
But, if a rotating frame of reference is mistakenly perceived as an inertial frame of reference, then what appears to be radial motion is actually straight line motion in an inertial frame with the rotating frame's apparent radial change in distance being perceived as due to a mysterious force.
The link Cat posted in reply #24 uses the "Bianchi cosmologies" which are the equations resulting from not assuming that the universe is isotropic when solving the field equations in General Relativity Theory. The authors claim that their work is the first to "consider all degrees of freedom in these solutions to conduct a general test of isotropy using cosmic microwave background temperature and polarization data from Planck." Their result is that it looks highly unlikely that the universe has "spin".
Not being able to check their assumptions, math or data myself, I have to take their word for it as the best effort to date to address my question. That does not mean that I am positive that no future study could come to a different conclusion when more is known or errors in math or modeling are uncovered. But, it is a reasonable result that comes from a reasonable effort to address the question. So, at this point, I am accepting the following:
1. It is a reasonable question that can be addressed.
2. It has been addressed in a very comprehensive (and complex) manner in the linked paper.
3. The conclusion is that there is high probability that the universe has no intrinsic spin (nor anisotropy in direction).
From my vague knowledge of things, I wouldn't think that 'spin' in terms of such a vast scale would be measurable. As far as I understand it, everything in the universe is moving in it's own direction, rotation, etc - so one cannot apply an overall 'spin' to it all.
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