10 ms·
Can rotation solve the Hubble Puzzle?
- hoseja 2y agoWait did nobody seriously consider rotation yet? Everything is rotating. Angular momentum is conserved.
- jvanderbot 2y agoIsotropy is a fundamental assumption that is very hard to let go of.
- exe34 2y agoWhere would the axis of rotation be?
- nodfyr 2y agoThat would imply a preferred direction in the universe (the axis of rotation) and thus anisotropy. 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.
- gitaarik 2y agoWell, the universe has an axis, found in the CMB: https://en.m.wikipedia.org/wiki/Axis_of_evil_(cosmology) https://en.m.wikipedia.org/wiki/Axis_of_evil_(cosmology)
- jfengel 2y agoThe article says right up front that the universe does not have an axis: However, a 2016 study compared isotropic and anisotropic cosmological models against WMAP and Planck data and found no evidence for anisotropy.
- gitaarik 2y agoThat was only one observation, most of the observations do indicate there is an axis
- lumost 2y agoRotation 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.
- exe34 2y agoand we would be at the center?
- theoreticalmal 2y agoMy dog is quite sure she’s at the center, if we’re trying to be specific
- shermantanktop 2y agoMain Character Energy? My cat has that too.
- layer8 2y agoThe center of a black hole lies in the future. It’s called a singularity, and the equations of general relativity break down at it. So no, we are not at the center.
- gitaarik 2y agoYeah, we are. https://en.m.wikipedia.org/wiki/Axis_of_evil_(cosmology) https://en.m.wikipedia.org/wiki/Axis_of_evil_(cosmology)
- AnimalMuppet 2y agoAre we in an infinite universe? I thought the current thinking was that it was finite but unbounded; that is, that it curved back on itself.
- 2y ago
- est31 2y ago> 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).
- BigParm 2y agoIf spacetime rotates, does that imply there being a centre of the universe?
- layer8 2y agoIf the universe is the interior of a black hole, one would assume so.
- irrational 2y agoAnd an axis.
- layer8 2y agoOr an axis.
- signalToNose 2y agoAnd my ax
- gitaarik 2y agohttps://en.m.wikipedia.org/wiki/Axis_of_evil_(cosmology) https://en.m.wikipedia.org/wiki/Axis_of_evil_(cosmology)
- pmontra 2y ago
- bostonwalker 2y agoI 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?
- dkural 2y agoThat 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.
- ziddoap 2y agoI 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)
- iainmerrick 2y agoThis comment has a good summary of the debunking: https://news.ycombinator.com/item?id=43540635 https://news.ycombinator.com/item?id=43540635 It's unfortunately rare for this kind of straightforward falsification to make it into publications aimed at the general reader. "A lie is halfway round the world before the truth has got its boots on," as they say.
- ziddoap 2y agoThanks. I was hoping for something a bit more authoritative than a reddit comment being copy/pasted to HN (e.g. an actual retraction, or a paper directly disputing the findings), but I'm guessing most of the community just ignored the paper due to the history of the author.
- 2y ago
- BurningFrog 2y agoIf I understand what I skimmed, the idea is that space-time itself rotates, not all the collective matter in it?
- jfengel 2y agoCorrect. 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.
- BurningFrog 2y agoThanks. These things really challenge my physics intuition!
- daxfohl 2y agoICYMI: a slick link from the article with a video that demonstrates how closed timelike curves work in Godel's time traversal solution to Einstein's field equations. https://iopscience.iop.org/article/10.1088/1367-2630/15/1/013063 https://iopscience.iop.org/article/10.1088/1367-2630/15/1/01...
- WhitneyLand 2y ago“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?
- layer8 2y agoAt 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.”
- daxfohl 2y agoGodel and Einstein were actually quite close.
- mcswell 2y agoThere's a scene in the recent movie Oppenheimer about that.
- TheRealPomax 2y agoIf your paper has a question title, it should be sent back to you with the note "change the title to summarize the paper".
- IAmBroom 2y agoAnd Betteridge's Law applies, so based on this alone: the Universe does not rotate.
- jinwoo68 2y agoUniverse 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?
- layer8 2y ago“Universe” is often used in the sense of “observable universe”.
- jinwoo68 2y agoI 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.
- olddustytrail 2y agoRotation isn't relative. You can tell how quickly you're rotating without reference to any other objects.
- carra 2y agoBut 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?
- olddustytrail 2y agoNope, rotation is not relative because it's an acceleration. There is no "space itself" because then you're assuming it is relative, like the speed of light. Basically you're trying to rediscover the aether. That was the question: light moves at speed C, but relative to what?
- 2y ago
- natch 2y agoRotation relative to what?
- analog31 2y agoI 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).
- natch 2y agoThanks! That makes sense, but didn't come to mind right away for some reason.
- quickthrower4b6 2y ago[dead]
- NoScopeNinja 2y ago[flagged]
- randomcarbloke 2y agobased on napkin math, the rotation they land on: 4.34 x 10^-20 rad/s is one order of magnitude (not a lot on a cosmological scale) slower than necessary for a causal disconnect at the boundary of the observable universe due to tangential velocity (at ~C) - obviously my maths could be off-by-one. Is this a reasonable conclusion?
- sojuz151 2y agoAnd the Hubble tension is around 4%, within a factor of 2 of that 10%. This sounds reasonable.