Does our universe have "spin"

Feb 7, 2022
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Just wondering if anybody has addressed this question.

We seem to see spin in everything from sub-atomic particles to black holes, not to mention galaxies.

So, it seems to me that spin should not be out of the question for the universe.

And, if the universe is spinning, wouldn't there be a fictitious "centrifugal force" that would tend to make it expand?

How would that compare to "dark energy"?
 
Feb 7, 2022
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COLGeek,

I do see that there have been discussions about spin here in the past. In particular, your second link went off the rails and was closed to further comments. It seems to have become bogged down in whether spin is an absolute or relative quality. There seems to have been some misunderstandings relating spin to "relativity" that missed the point that "relativity" is conceptualized between inertial frames of reference, and that a rotating frame is not an inertial frame - it involves fictional forces.

So, in the hope of not repeating the now-closed discussion, my intent for this thread is to address whether we can expect the universe to have spin, whether a spin in the universe could be perceived as such by us here on Earth, and whether it would have effects that could be mistaken for "dark energy" - or at least complicate measuring the effects of "dark energy" in a quantitative manner.
 
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COLGeek

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Apr 3, 2020
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Fair enough. Just sharing that this topic has come up in the recent past. Searching for previous discussions can help frame a more current iteration of a topic.
 
Feb 7, 2022
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Cat, I think we are just going to have to disagree on that. The reason is that we really don't know that inertia can be "relative" in a spinning universe. We certainly know that spin can be detected in a smaller closed system inside the universe by the forces that can be detected even without seeing outside of the spinning closed box. So, I don't see any a priori reason to say that a universe cannot have spin, or that we could not detect its effects.

However, detecting its effects without misinterpreting them might be difficult. For one thing, it would be covering an extremely large volume, and we are restricted to an extremely limited point of view from within that volume, currently and probably forever. So, if its manifestations are different in different regions, we would have a hard time figuring that out.

That is really my question - could we figure it out if it is really there?
 
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Catastrophe

"There never was a good war, or a bad peace."
Considering that we only have the observable universe in view, how can we possibly comment on The Universe. Politely, it would be speculation at best.

"That is really my question - could we figure it out if it is really there?"
No. ;)

Cat :) :) :)
 
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Considering that we only have the observable universe in view, how can we possibly comment on The Universe. Politely, it would be speculation at best.

"That is really my question - could we figure it out if it is really there?"
No. ;)

Cat :) :) :)
"We certainly know that spin can be detected in a smaller closed system inside the universe" My emphasis.

So what? Not wishing to be impolite. :)


Cat :)
Ok, try to think of it as a limiting situation for experiments that we can actually do.

I am assuming that you agree that a person can detect that he/she is in a rotating frame of reference when in a small, closed space with no visibility to the outside, by seeing that a mass set into unperturbed motion follows a curved path instead of a straight path.

Jut think about expanding that enclosed space until you reach the edge of the universe. Unless something suddenly changes when the boundaries of your test space reach the total space in our universe, you will get the same result for the universe that you can get in the smaller space that is a subpart of the universe.

Granted, detectability in any amount of space requires the ability to see enough deflection from a straight path to exceed your measurement threshold.

The thing that would get difficult in large amounts of space would be determining what is a straight line. Typically, we assume that a laser makes a straight line in space. But, we do know that light bends around mass. So, if light does not travel in mostly straight lines across our universe, then we might not be able to detect that matter is not traveling in a straight line, either. However, from what I keep reading, most people agree that our universe is "flat" rather than "curved". On the other hand, people used to think that was true of the Earth's surface at one time, and we laugh at them today. Maybe people will be laughing at us about space being flat some day, too.
 

Catastrophe

"There never was a good war, or a bad peace."
No, sorry. Standing at the centre of your own observable universe, there is nothing to see outside your observable universe (by definition). There is no correspondence whatsoever with a small closed space.

There is no external frame of reference.

You cannot observe or interact with an 'outside' when there is no 'outside'.

Cat :)
 
Feb 7, 2022
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Cat, what I posted does not require any thinking about what is outside the universe, so I am not understanding your objection.

What I posted is only observations inside the universe, taking the experimental volume from something we could test on Earth and conceptually expanding that volume to fill the entire universe. At what point in that expansion process do you think the result would change, and why?
 

Catastrophe

"There never was a good war, or a bad peace."
Unc,
" a person can detect that he/she is in a rotating frame of reference when in a small, closed space with no visibility to the outside, by seeing that a mass set into unperturbed motion follows a curved path instead of a straight path."

If you are in a small closed space. can you detect a mass following a curved path (on that scale)?

"taking the experimental volume from something we could test on Earth and conceptually expanding that volume to fill the entire universe."

It would stop when you can no longer see the walls - when you cease to have an external frame of reference?

I am a bit concerned that these seem contrived, with no relation to reality??

Cat :)
 

Catastrophe

"There never was a good war, or a bad peace."
On consideration, I am standing by my post #5, which I only entered because I thought (still do) that it settled an old question in a different way.

No (spin), because there is nothing outside the Universe (by definition) to provide a background for comparison. Semantically, it is a 'no sense' = meaningless question.

If that is not so considered, I don't want to get drawn into the same old arguments.

I am quite willing to delete #5 before the option runs out. Of course any inclusion of it in other posts will remain, but it would show that I don't want to be responsible for trawling over the same old stuff.

Cat :)
 
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I am not considering using the walls as a reference for "straight". I would compare the path of the mass to the path of light created by a laser. So long as we can call the light path "straight", I think we have a reference without relying on any walls anywhere. The only reason I used the concept of walls was as a block to getting any visual reference from outside the experiment volume. No longer necessary to have view blockers when considering the whole observable universe.
 
Nov 19, 2021
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If the universe is spinning then it must be spinning around a selected point. If we happened to be at that point then no amount of red shift measurements could reveal the spin since redshift measurements are along our line of sight and any spin centered on us is transverse to our line of sight.
Suppose the spin axis was near Polaris and the spin axis was parallel to and in the same direction as the Earth's spin axis, then if we looked to the east we would see galaxies receding from us and if we looked to the west we would see galaxies approaching us.
We do see half of the CMB approaching us and half receding from us. Perhaps we are not moving within the universe, perhaps it is spinning.
This is a tough one to wrap one's mind around.
 
Feb 7, 2022
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Yes, it is definitely hard to conceptualize.

"Spin" to me implies an axis of rotation.

I would naturally think that the earth is unlikely to be on any axis of rotation for the entire universe.

But, we are in the center of our own portion of the universe that is rendered visible by the events that are assumed to have made it transparent to light everywhere at the same time.

Assuming that the axis of rotation for the universe is not passing through earth, and that the sources of the cosmological background radiation that we are seeing now are also rotating, but not on an axis that goes through the Earth, what should we see in the way of red-shift from this vantage point?

Part of my problem is trying to decide if "spin" is like a pinwheel, with constant angular velocity along the radius to the axis, or instead, like many masses orbiting a central attractor, such as we see around a black hole. Heck, if we are orbiting around some huge mass, would we even be able to see it beyond the visibility horizon of the cosmic background radiation.

I am hoping that the Webb Telescope will be able to see more details around some local black holes and out toward the postulated background radiation source such that we might get a better feel for what really is going on.
 
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COLGeek,

There seems to have been some misunderstandings relating spin to "relativity" that missed the point that "relativity" is conceptualized between inertial frames of reference, and that a rotating frame is not an inertial frame - it involves fictional forces.
It's an interesting thread, but just as an aside, I don't like the use of the commonly used term 'fictional forces' to describe the forces present in a rotating (non-inertial) frame of reference, as that implies they are not 'real'. These forces are perfectly real in that rotating frame of reference, and are experienced by objects and can be measured in that frame of reference. :)
 
Feb 7, 2022
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I do understand the language issue, but I don't know what the alternative would be without inventing another word, which would tend to make most people lose the point.

The idea to be conveyed is that the person in the non-inertial frame that "thinks" (s)he is in an inertial frame will need to devise a "law of nature" that accounts for what is perceived as a force, but is really a lack of force that would be needed to make things act like the observer was in an inertial frame of reference. So, it is not a real force in the sense that it's depiction is not the way that the laws of nature really work.

The Coriolis Force is a good example. Even if you realize that the Earth is a sphere (sort of), if you still thought that it was stationary in space and the Sun revolved around it, then you would need to make a "law" of nature that things in motion try to turn toward the right when north of the equator, and leftward when south of the equator.

But, if people tried to use that "knowledge" in other situations, it would not work properly if the other situations were proper inertial frames or even rotating frames with different periods of rotation. Only by realizing the rotation as an important factor can an observer develop an understanding that is universally applicable.

And, that is the point of many of the questions I have regarding cosmology. Basically, I am asking "Are we missing something?" I think that question should always be kept in mind as people try to develop scientific understanding, especially when they get results that appear enigmatic, or their equations "blow up" for conditions that are actually observed or "required" by the theory in use.
 

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