A spinning Universe?

  1. From a universe according to General Relativity can we ascertain if the Universe can be said to be spinning?

    Spinning relative to what is a tough question - I would say perhaps a rate of spin relative to the age of the Universe might give a framework if it can be agreed that say 1 second after the BB the Early Universe was spinning or perhaps more properly could at least be said to have had Angular Momentum as it expanded?

    I have no Grand Theory attched to this question I was just - as always - curious.
     
  2. jcsd
  3. selfAdjoint

    selfAdjoint 8,147
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    The famous logician and pal of Einstein, Kurt Goedel devised a spinning Einstein style universe and showed that it contained closed timelike paths - code for achievable time travel.
     
  4. That sounds interesting - time travle is always interesting though doubtful- what say the theorists?
     
  5. Garth

    Garth 3,443
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    A Machian view would say that the universe could not spin as a whole as it would need to rotate relative to something else; although one 'half' could rotate relative to the other 'half'.

    Goedel's model could then, in a Machian view, to be construed as a refutation of GR.

    Alternatively, from a GR point of view, it could construe a refutation of Mach's Principle. Perhaps Gravity Probe B will resolve the issue?

    Garth
     
  6. Nereid

    Nereid 4,014
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    How?

    More precisely, what limits could the 'best' (= most sensitive) results from GPB set on the rotation of the universe?

    On another tack, there is at least one research effort underway to measure 'local rotation', using ring lasers ... could that work also constrain 'universal rotation'?

    Finally, didn't I read that Hipparcos set some limits (not very stringent) on rotation of FK5? (I'll check later ...).
     
  7. Garth

    Garth 3,443
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    My cryptic reference to possible non-GR results of that experiment! -and possible Machian alternative results.

    As I said on another thread "Mach's Principle", my post #37:
    Garth
     
  8. Thanks guys

    When do we get the results of this probe you refer to?

    PS: If the Universe is spinning would there be a different rate of spin from the early universe to the present Universe?

    If expansion is increasing what would occur to the spinrate?
     
  9. Garth

    Garth 3,443
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    The experiment will end this (northern) Summer. Analysis of the results may take several months and results should be published early next year (06). However everything about GPB has taken twice as long as expected so I wouldn't hold your breath!
    If there is an absolute inertial frame relative to which the universe is spinning, and in which angular momentum is conserved, then its spin rate would slow down with expansion. Conversely as you plot back into the Big Bang the spin rate should go up - infinitely so as t -> 0?? Perhaps that is a possible cause of a bounce?

    Garth
     
  10. Thanks Garth - I will look forward to these fascinating results (or more correctly the results of this fascinating experiment!)

    Anyone else have any thoughts on the "bounce" Garth mentions?
     
  11. Garth

    Garth 3,443
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    Of course if would be a pancake bounce normal to the axis of rotation.

    Garth
     
    Last edited: Apr 21, 2005
  12. i have thought for years that it is spinning personally. and i thought this because i knew that galaxies, and everything else, is spinning. so the question is if a galaxy is spinning, then to what is its spin relative? and as far as what is relative to the spin of the universe that is impossible to ever prove. however, it is possible that one universe is spinning realtive to another, or to something bigger. we will just never know. but what we do know is that everything we know of is made of smaller couterparts down to the quark level. so it would make sense that our universe is maybe something similar to a cell in that makes up something even bigger. because to a cell our body would be a universe. and since everything is made on the atomic level, perhaps our universe makes up a bigger part of the "atom" per se.:rofl:
     
  13. JesseM

    JesseM 8,491
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    A rotating universe in the context of general relativity isn't rotating in quite the sense we usually think of it--there's no center of rotation, for example. As this page says:
     
  14. What an odd remark from someone writing about science. :smile:
     
  15. An interesting topic ..
    When one talks about a spinning universe, does one mean that all the galaxies and mass are spinning or does one mean that space (in between the galaxies) is also spinning ? If space itself is spinning, what does this actually mean ? There exists in general relativity also the so-called "frame-dragging" effect (a topic of investigation for the gravity probe B experiment). Could this also be interpreted that space is actually spinning around a rotating body ?
     
  16. Chris Hillman

    Chris Hillman 2,334
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    "Rotating universes"

    Hi, Always curious,

    Just thought I'd recommend some more reading:

    You can find a new arXiv eprint with fabulous illustrations of closed timelike curves CTCs in the Goedel lambdadust solution as http://www.arxiv.org/abs/gr-qc/0611093. The classic description is in Hawking and Ellis, The Large Scale Structure of Space-Time, and if you search the arXiv you should find a dozen or so eprints discussing various aspects of this fascinating solution.

    I also recommend Cuifolini and Wheeler, Gravitation and Inertia, for more about Mach's principle, frame dragging, gravitomagnetism, and rotating cosmological models, even though I don't feel this book comes up the high standards of exposition set in the classic textbook by Misner, Thorne, and Wheeler, Gravitation, Freeman, 1973.

    That's not true in general; the so-called LRS (locally rotationally symmetric models) and the well-known Van Stockum dust are examples of cosmological models in which the matter (source of the gravitational field) is rotating about an axis with a definite location "in space". However, the Goedel lambdadust is homogeneous (not isotropic), so it does have the property you mentioned.

    The issue of how to define "rotation" in curved spacetimes gets quite tricky and much ink has been spilled--- unfortunately, some contributions seem to involve "independently committing" the same errors which have been made (and corrected) in the past, so discussion can easily become contentious.

    As always, the local versus global distinction is critical. There are distinct notions of "rotation" which are local in the sense of "jet space", principally vorticity (MTW, Hawking and Ellis, the book by Eric Poisson, A Relativist's Toolkit, are all good sources for the kinematical quantities known as the vorticity tensor, expansion tensor, and acceleration vector), and neccessarily more sophisticated notions which are global.

    One thing to watch out for (for those who know what these buzzwords mean): in many "rotating" dust models, the "obvious" coframe read off the metric is often already inertial and even comoving with the dust particles, but the frame may be spinning. With luck, as in the Goedel lambdadust, you can "despin" the frame by applying, as you run along the world line of each dust particle, just the right rotation as a function of proper time about one of the spatial frame vectors. Here, note that in curved spacetimes, nonspinning inertial frames correspond to Lorentz frames in flat spacetime. Spinning but inertial frames correspond to, well, you probably get the idea.

    Similar remarks hold for circularly polarized plane waves. Speaking of which, the Osvath-Shuecking circularly polarized gravitational plane wave solution is often touted as a "rotating" cosmological solution (although it is an exact vacuum solution, indeed a Petrov type N vacuum, not a fluid solution, so no matter is anywhere in sight!).

    Chris Hillman
     
  17. Supposing the universe rotates - and the galaxies rotate around its centre - and the solar systems rotate around the centre of galaxies - and the planets rotate around the centre of solar systems - is there some crazy math that could posit the earth as the centre of it all?
    No I am not a creationist - just thought it would be fun to try.
     
  18. ZapperZ

    ZapperZ 29,996
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    First of all, you're posting in a thread that had its last activity in 2006!

    Secondly, why even bother with such a thing since we already know that the earth is NOT the center of the solar system, much less, the "center of it all"? Is there a reason to want to do this meaningless exercise?

    Zz.
     
  19. Just the math.

    Can concentric circles end up with a point of the edge of the first circle as the centre?
     
  20. I apologize for digging up a 5 year old thread as my first post but looking into this subject is what lead me here. I have always believed that the galaxies may orbit some type of center and more so that the universe is rotating and possibly in orbit along with others around some larger body. I wasnt sure (although I assumed) that the question had been put forth by anyone else.


    Also, Hello. Holland is actually my name. I am a 33 yo Texan, living in Nicaragua with enough free time on my hands to ponder the workings of the heavens. I look forward to reading the information provided in this forum.
     
  21. bcrowell

    bcrowell 5,805
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    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
     
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