> All objects within our universe rotate, including planets, stars, solar systems, galaxies, and galaxy clusters. Moreover, black holes, spherically symmetric objects with horizons, display near maximal rotation as presented by Daly (2019). The idea that everything revolves [...] naturally extends to the whole universe, as hinted by recent claims of anisotropic Hubble expansion in X-ray observations by Migkas et al. (2021). Furthermore, a plausible syllogism is that the universe has near-maximal rotation, motivated by cosmologies where the universe is the interior of a black hole (Pathria 1972).
> a plausible syllogism is that the universe has near-maximal rotation
And also from the abstract:
> Curiously, this is close to the maximal rotation, avoiding closed time-like loops with a tangential velocity less than the speed of light at the horizon.
That's weird considering that in lambda CDM the universe's accelerating expansion implies that stuff falls out of our observable universe, which implies that there is more stuff beyond the edge of the observable universe, and anyways there is no center of the universe and we are only at the center of our observable universe, which also further implies that there is stuff beyond the observable universe. Are they saying that our observable universe has a rate of rotation such that the tangential velocity at the edge is about the speed of light? What about the stuff beyond the edge? And as u/BigParm wonders, doesn't having the whole universe rotate imply a center? Surely we can't be at that center. But maybe there can be an illusion that we are at the center of rotation.
Wouldn't the center be the Big Bang and the 3D Universe at the current time (if Relativity lets me write about a current time) be the 3D surface of the 4D sphere (or spheroid) that the Big Bang is creating by keeping to expand?
Which would undercut practically all of modern physics. Really fundamental conservation laws like momentum and energy rely on the universe being equal in all directions. If it has a central axis, that does not hold.
So if that holds, it's potentially a major pointer to the very origins of the universe itself. But it's also one of those extraordinary claims that require extraordinary proof. I strongly doubt that this will stand up to scrutiny -- though I'll certainly be pleased if it turns out be true, because that will be a major advance in our understanding.
If everything started from a singularity that had a axiomatically uniform rotation, you might not be able to assess the center "axis" based from inside spacetime itself
This seems to be a variation of Mach's principle, which is one of the closest things to philosophy in physics!
To say that the universe rotates usually implies that it rotates with respect to something external. If we limit ourselves to the visible universe, this would mean that mass outside our light cones can actually influence us, by means of building the frame of reference that allows us to say that the universe rotates!
There is. The center of the observable universe is earth. Every alien civilization will see themselves at the center of thier observable universe. And each will observe the same rotation in faraway objects. Relativity makes things strange.
If you have two stars orbiting each other, they orbit a centre of gravity and they will probably both be rotating in the same direction as their orbits.
Is that a meaningful centre for anything else though?
Correct. Though the matter in it would also move, dragged along by the space-time.
It's much like the expansion of the universe, which is separate from the ordinary momentum of the objects within the universe. But the objects within the universe do move apart along with it.
I seem to recall there was an article posted here recently which noted that galaxies have a preferred direction of rotation. Seems like the universe itself rotating could be a reason why?
That article is by a crank. People pointed out that he cherry-picked the galaxies, and no one else who looked at the data objectively saw any evidence of preference for a rotation direction.
I looked around (Smithsonian, space.com, astronomy.com, etc.), but nowhere has any mention of people disputing the findings, do you have a link? Who is "people" in this case?
(I was/am skeptical just because it's a single-author study with pretty spectacular results, and have been keeping an eye out for any followups, but must have missed them)
Universe is called universe because it is the only one. Everything that exists should be part of the universe. When we say the universe rotates, what does it mean? Rotate relative to what? Does it mean that there's a larger "universe" that contains ours?
But even then you can only tell that you are rotating relative to space itself. If I understand correctly here we are speaking about the space itself rotating, so that would not be possible unless something else contains our universe's space, right?
Nitpick: "Atoms are called atoms because they have no subdivisible parts".
Oops, it turns out we used the name too soon.
When people say "universe" these days they mean the "visible universe" (or maybe the visible universe plus the stuff we're sure is there, but that falls outside our light cone now) - and not the original definition of the word anymore.
I don't think the paper claims that it's the observable universe that rotates. Does it? It'd be awkward if only the observable universe rotates. Observable universe is not special. It's observable just because it is "close" to the Earth.
I consider this to be a good question, but with a reasonably familiar answer:
Rotation is absolute. Unlike linear motion, you can tell if you're sitting in a rotating frame of reference or not. Experiments such as the Coriolis force, and Foucault's pendulum, are demonstrations of this principle.
In fact, a historical oddity is that when this idea was nailed down by both theory and experiment, the Catholic Church dropped its ban on heliocentrism. (Not that it mattered, the horse had already left the barn).
Rotation implies a great many observables and properties of the universe. There would be a cosmic axis, which implies a cosmic center and a cosmic north. Both concepts that are problematic in an infinite universe. If the universe is in fact inside of a black hole of a different universe - some of these problems go away as the Hubble volume would be the finite boundary of the universe.
“We show that a Gödel inspired slowly rotating dark-fluid variant of the concordance model resolves this tension…”
Gödel wait what? I thought of him as “only” the logician who killed Hiblert’s dreams and caused people to question the very foundations of mathematics.
Dude then took up physics as a hobby and trolled Einstein by discovering closed time-like curves?
At the level of what he did, physics is “just” math (finding solutions for Einstein’s general-relativity equations).
Also, from Wikipedia: “At age 18 [so around 1924], Gödel joined his brother at the University of Vienna. He had already mastered university-level mathematics. Although initially intending to study theoretical physics [we can assume that’d include an interest in relativity at that time], he also attended courses on mathematics and philosophy.”
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And also from the abstract:
> Curiously, this is close to the maximal rotation, avoiding closed time-like loops with a tangential velocity less than the speed of light at the horizon.
That's weird considering that in lambda CDM the universe's accelerating expansion implies that stuff falls out of our observable universe, which implies that there is more stuff beyond the edge of the observable universe, and anyways there is no center of the universe and we are only at the center of our observable universe, which also further implies that there is stuff beyond the observable universe. Are they saying that our observable universe has a rate of rotation such that the tangential velocity at the edge is about the speed of light? What about the stuff beyond the edge? And as u/BigParm wonders, doesn't having the whole universe rotate imply a center? Surely we can't be at that center. But maybe there can be an illusion that we are at the center of rotation.
Which would undercut practically all of modern physics. Really fundamental conservation laws like momentum and energy rely on the universe being equal in all directions. If it has a central axis, that does not hold.
So if that holds, it's potentially a major pointer to the very origins of the universe itself. But it's also one of those extraordinary claims that require extraordinary proof. I strongly doubt that this will stand up to scrutiny -- though I'll certainly be pleased if it turns out be true, because that will be a major advance in our understanding.
To say that the universe rotates usually implies that it rotates with respect to something external. If we limit ourselves to the visible universe, this would mean that mass outside our light cones can actually influence us, by means of building the frame of reference that allows us to say that the universe rotates!
If you have two stars orbiting each other, they orbit a centre of gravity and they will probably both be rotating in the same direction as their orbits.
Is that a meaningful centre for anything else though?
It's much like the expansion of the universe, which is separate from the ordinary momentum of the objects within the universe. But the objects within the universe do move apart along with it.
These things really challenge my physics intuition!
(I was/am skeptical just because it's a single-author study with pretty spectacular results, and have been keeping an eye out for any followups, but must have missed them)
Deleted Comment
Oops, it turns out we used the name too soon.
When people say "universe" these days they mean the "visible universe" (or maybe the visible universe plus the stuff we're sure is there, but that falls outside our light cone now) - and not the original definition of the word anymore.
(Not that we have "found" anything else yet.)
They are aptly named.
Rotation is absolute. Unlike linear motion, you can tell if you're sitting in a rotating frame of reference or not. Experiments such as the Coriolis force, and Foucault's pendulum, are demonstrations of this principle.
In fact, a historical oddity is that when this idea was nailed down by both theory and experiment, the Catholic Church dropped its ban on heliocentrism. (Not that it mattered, the horse had already left the barn).
Dead Comment
There are stringent constraints on anisotropy from the cosmic microwave background.
In particular, one can use the Doppler effect to check whether the CMB dipole is compatible with our velocity with respect to the CMB frame.
https://en.m.wikipedia.org/wiki/Axis_of_evil_(cosmology)
The observation could also be due to an area of relatively high density inside an area of relatively no density.
Gödel wait what? I thought of him as “only” the logician who killed Hiblert’s dreams and caused people to question the very foundations of mathematics.
Dude then took up physics as a hobby and trolled Einstein by discovering closed time-like curves?
Also, from Wikipedia: “At age 18 [so around 1924], Gödel joined his brother at the University of Vienna. He had already mastered university-level mathematics. Although initially intending to study theoretical physics [we can assume that’d include an interest in relativity at that time], he also attended courses on mathematics and philosophy.”