M Sunday Morning Thought: Could the Universe Be Rotating?

[DarioC]

Just reading the Physorg article on the new numbers on the expansion of the universe.

While sipping my coffee a thought came to me. Has anyone considered the possibility that the entire universe is rotating in a way similar to galaxies? Probably old hat, right?

Just my thought on a quiet, rainy, Sunday morning.

DC

 

[edgepflow]

The "Godel Solution" is an exact solution to the Einstein field equations for a rotating universe. However, this solution does not have Hubble expansion so it is not considered physical.

 

[Farahday]

Clockwise or counter-clockwise. And how would you know if you were viewing it upside-down?

 

[DarioC]

Part B: Are there known/observed galaxies that rotate with sufficient velocity to disperse the stars. I would guess not, as the galaxy would never have formed in the first place.

Next: Would a rotating universe exhibit centrifugal force? I understand what you are saying about this mathematical theory, but that only "proves" that particular theory does not exhibit the Hubble expansion, not that other theories or physical reality of a rotating universe would not exhibit/include/demonstrate Hubble expansion.

DC

 

[bcrowell]

FAQ: Can we tell whether the universe is rotating?

It is possible according to general relativity to have cosmologies in which the universe is rotating. This is a non-Machian feature of GR, since the rotation is not relative to anything else. There does not have to be a center of rotation, and such solutions can be homogeneous. One of the earliest cosmological solutions to the Einstein field equations to be discovered was the Gödel metric, which rotates and has closed timelike curves.

Solar-system observations[Clemence 1957] put a model-independent upper limit of 10^-7 radians/year on the rotation, which is an order of magnitude too lax to rule out the Gödel metric. Observations of the cosmic microwave background's anisotropy impose a limit that is tighter (perhaps 10^-9 rad/yr[Su 2009] or 10^-15 rad/yr[Barrow 1985]), but model-dependent.

Because all of the present observation are consistent with zero rotational velocity, it is not possible to attribute any prominent cosmological role to rotation. In particular, centrifugal forces cannot contribute significantly to cosmological expansion.

Clemence, C.M. (1957). 'Astronomical Time', Rev. Mod. Phys. Vol. 29, p. 2

Hawking, S.W. (1969). 'On the Rotation of the Universe', Mon. Not. R. astr. Soc. Vol. 142, p. 529.

Collins, C.B., and Hawking, S.W. (1973). 'The Rotation and Distortion of the Universe', Mon. Not. R. astr.Soc. Vol 162, p. 307.

Barrow, J. D., Juszkiewicz, R., & Sonoda, D. H., "Universal rotation: how large can it be?," 1985 -- http://adsabs.harvard.edu/full/1985MNRAS.213..917B

Su and Chu, "Is the universe rotating?," 2009, http://arxiv.org/abs/0902.4575

 

[marcus]

Dario,

I think it's possible you might avoid wasting some time if you read Lineweaver's basic article on cosmology that I have a link for in my signature at the end of this post.

Just a suggestion. It is the link with "charley" at the end. A Scientific American article called Misconceptions about the Big Bang. If you go there, the first page is blank, so scroll down.

A lot of people have found that article by Charley Lineweaver helpful.

It is important to notice that as far as we know there is, in our space, no center of the expansion of distances. There is no direction in the sky that you or I could point and say "the center is over there."

If there were rotation where would the center be? If there were centrifugal force, in which direction would the force be pushing our galaxy?

Also it is important to realize that the distances to most known galaxies (as of today) are increasing faster than the speed of light. This is an unavoidable consequence of the Hubble Law v = Hd, and the measured value of the Hubble constant H. This is just a basic fact.

If you want to discuss standard mainstream cosmology, then you have to start somewhere. That short Lineweaver article is a good place. It is simply written, free, online, well illustrated, and covers many of the basics.

What's not a good place to start is some words you heard. Like "Big Bang". The words often give people a false mental image. Or watching something on television. It's easy to get the wrong mental pictures and waste time on misconceptions. I don't KNOW that you are doing that, but I'm suggesting you read that article just as insurance. As a preventative measure, just in case
=====================

Also if not too much trouble, please give us the link to the physorg article about "new numbers on the expansion of the universe". I didn't see a recent physorg article about that and I'd be interested to look it up?

 

[DarioC]

http://www.physorg.com/news/2011-03-hubble-alternative-dark-energy.html

Well, I must admit that my question was not well-pondered by me before asking or I would not have asked. I should have thought of the no-center expansion at least. But it did bring up some good references. Thanks all for those.

I am familiar with some relativity and cosmology concepts from reading Albert, Hawking, Penrose, and Greene, so I don't take the "big bang" literally.

DC

PS: Let's try this. If the universe started as a finitely small OR a infinitely-small point and expanded, it should, regardless of elapsed time, still be of a finite size. If it is of a finite size, then it must have a center. Yeah, I know, flat vs curved, but it is still an interesting point from a layman's view.

Then on the other hand; if the universe is curved, that would imply that it was always curved, all the way back to the infinitely-small point. A curved, without end, limits, or edges, infinitely-small point; I rather like that.

 

[bcrowell]

If it is of a finite size, then it must have a center.

Closed FRW cosmologies have finite spatial volume, but they don't have a center.

 

[marcus]

http://www.physorg.com/news/2011-03-hubble-alternative-dark-energy.html

...should, regardless of elapsed time, still be of a finite size. If it is of a finite size, then it must have a center.

... A curved, without end, limits, or edges, infinitely-small point; I rather like that.

Thanks for the link. It let's us know where you are coming from, since you began your first post with a reference to that physorg news item.

The technical article, in case you haven't looked it up, is this:
http://arxiv.org/abs/1103.2976

I want to emphasie what BAPowell said about "finite size does not imply a center".

Also cosmologists don't say that the U was once an infinitely small point. You still hear that in popularizations, at least about the portion of the U we presently observe, if not the whole U.

The reason they don't assume infinitely small point is that classical (unquantized) Gen Rel breaks down at extreme density and gives meaningless results. It fails before the "infinitely small point" is reached. So there is no reason to believe it. So scientists (among themselves) do not believe that. You don't believe stuff if there's no evidence.

One place that explains that is the Tale of Two Big Bangs essay at Einstein-Online that I have a link to in my sig. It is only one page and simply written, no math. Please read it. Then you may see statements like the following in a different light:
"A curved, without end, limits, or edges, infinitely-small point; I rather like that."



Hopefully you really do rather like the idea (except nobody says infinitely small point) because expansion can very well have begun with a spatially finite boundaryless U. Some models (which have not been observationally ruled out) show that for the start of expansion.
Conceiveably that might be the accepted picture some day, in which case if you rather like it already you'd be ahead of your time.

Other models show an infinite volume U at the start of expansion. One might expect that in time some of the alternatives will be observationally ruled out.

I don't know of any model where expansion begins with the whole U is an infinitely small point. That's just what you get in popularizations.

 

[DarioC]

I don't believe the small point origin either, but I understand it was originally a desired objective. It just doesn't happen to be workable as a solution, but I don't believe it for a different reason.
I occurs to me that if the rules fall apart at some certain "compression limit" perhaps that is where the cycle (if any) reverses. That is, if one intends to believe in multiple cosmic expansion cycles, which I do.

It also occurs to me that perhaps there could be multiple differentiated areas of a larger universe where some areas are expanding and other areas are being "compressed." That, of course, would require abandoning the big bang theory. I would wager someone could work that out mathematically, chuckle.

Cosmology is certainly interesting, but I think one should not take anything as an absolute, as drastic changes and reversals seem to come up at regular intervals. I just try to enjoy the show at a level that I can understand.

DC

 

[Tanelorn]

"I just try to enjoy the show at a level that I can understand."

Me too!

I wondered, roughly, how many people are currently researching and advancing the field of Cosmology, by this I mean members of the top rank(s)?