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Limit to Expansion of the Universe

  1. May 9, 2010 #1
    Thought experiment on a limit to the expansion of a Rotating Universe/Cosmos.

    Assumption: Let's say whether true or not, the entire Universe/Cosmos rotates about some axis. (The point from which the Big Bang happened, was a tortional explosion, i.e. it was spinning as it happened)

    As anyone who has ever looked at a CD or Record spinning knows, a sticker placed at the edge of the record is moving faster (going through a larger distance in the same amount of time) as a sticker placed closer to the center of the record.

    We also understand very well that the speed of light is the fastest velocity limit for any particle.

    Therefore, it stands to reason then that any particle at the edge of the universe, also cannot go faster than the speed of light. If the Universe is spinning, then that can only mean that the Universe cannot expand past a point whereby any particle at the edge of the universe revolves around the center of the Universe at a speed faster than that of light.

    Hence at the edge of a spinning expanding Universe, time will eventually come very close to standing still AND the Universe must at some point stop expanding such that any particle at the edge does not have the opportunity to go along a circumference of the Universe at a speed greater than the speed of light.

    If the spinning Universe continues to expand past the point of no expansion, then what happens to a particle at the very edge? I would guess the following:

    1) The particle must somehow stop revolving relative to the center of the Universe, even as the rest of the Universe closer to the center still revovles, possibly (along with any other particle with the same predicament) tearing the fabric of the universe at that point.

    2) The particle DOES achieve speeds faster than the speed of light...possibly going backward in time or achieving "imaginary" or negative mass. But any such particle, if it could exist, would also likely have anti-gravity forces. If you imagine a boundary of such particles around the spinning Universe, then these particles must somehow also contain the expansion of the Universe, via the anti-gravity forces.

    Therefore, **if** the Universe is indeed rotating around an axis, it must at some point stop expanding...it cannot expand forever. Now whether it contracts at that point, is another question all together.

    Krombacher
     
  2. jcsd
  3. May 9, 2010 #2

    DaveC426913

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    There are a LOT of preconceptions about a rotating universe that you may want to come to grips with (there is quite a bit of study about this that you can read up on). But aside from that, let's just pick at something within your argument that you should realize is inconsistent.


    Why would particles approaching c behave any differently here than anywhere else? Particles approach c, they experience time dilation, they cannot accelerate at the same rate. This is what happens every time we fire them in an accelerator, there's no "tearing" of any "fabric".

    The water near the edge of a bowl of spinning water is slowed by friction with the bowl's inner surface, so it cannot stay in lockstep with the rest of the water. Eventially you get a highly-attenuated spiral. What's wrong with that?
     
  4. May 9, 2010 #3
    Hi Dave,

    You said "particles approach c, they experience time dilation, they cannot accelerate at the same rate"

    But to a point. If a rotating universe expands so much so that time dilation is at point where time has halted, then there cannot be any more time dilation, right?

    The water near the edge of a bowl of spinning water...is tearing the fabric of the water, is it not. It's like suddenly hitting the brakes at the very edge.

    Finally with regard to "a LOT of preconceptions about a rotating universe", remember that all motion is relative. So we may never really know if the universe is actually rotating or not, as the "thing" that the universe would have to be relative to is something outside of the universe. If the big bang had any torsional forces, i.e. the singularity was spinning as it exploded, is there any way we would know?
     
  5. May 9, 2010 #4

    DaveC426913

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    This never happens. c can be approached but never reached. It is not to a point; it is a continuum; to infinity.

    Analogies only go so far. What is this "fabric" that gets "torn"? Spacetime has no such construct outside of Star Trek.

    Note you answered your own question:

    First:
    the "thing" that the universe would have to be relative to is something outside
    Then:
    the singularity was spinning as it exploded

    If you claim the first, you cannot then claim the second, since the singularity had no external referent.


    Really, there's lot of reading to do about this very concept. It's not a simple matter. I can point out internal flaws in your argument only so long before ultimately it will come down to flaws that require learning about the subject beyond Newtonian Mechanics.
     
    Last edited: May 9, 2010
  6. May 9, 2010 #5
    David,

    Well you're making my point. You said: "C can be approached but never reached" HENCE a rotating universe MUST stop expanding. Otherwise C would be reached. See? My point is that a rotating universe cannot expand forever.

    I don't see any internal contradiction with a spinning big bang or a spinning Universe, relative to something outside the universe/big bang.
     
  7. May 9, 2010 #6
    As to "fabric that gets torn", perhaps I should instead ask this question:

    If the Universe is spinning and expanding, and at some point must stop expanding or it will violate c, then particles at the edge must stop spinning about the axis with the rest of the universe, so that they do not violate c.

    Wouldn't this cause some sort of signal, i.e. massive electromagnetic radiation, or something (torn fabric) which would signal to us on earth that we have 1) reached the maximum expansion of the universe and 2) the Universe spins?

    Krombacher
     
  8. May 9, 2010 #7

    DaveC426913

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    Note also that, for the universe to be rotating, there would have to be an axis, which means certain points (along the axis) would be special, and it would be possible to locate this centre of the universe.

    This violates relativity as we know it. And if relativity is wrong, then our problem of relativistic time dilation at the edge just ... goes away!
     
  9. May 9, 2010 #8

    DaveC426913

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    This does not follow.
    The matter at the edge of the universe is moving near c tangentially. That does not impose any limit on its expansion radially.

    That is, unless you're thinking of a rigid disc...


    Let's say I use my hand to start a small whirlpool in a lake. I get more and more vigorous, causing the whirlpool to grow ever larger. At some point, the edge rotating water will be far enough from my location that the water's speed is affected more by the stationary water outside, than by the moving water inside. The water at the edge will still move in a circle but its speed will not increase beyond a certain amount (dependent on the vicsoity of water). The water at this distance will fall out-of step with the inner rotation of the whirpool, though it will continue moving. The whirpool's radius can expand without limit, but the speed of the water at its edge will approach closer and closer to some maximum speed limit.

    i.e. there is no such correlation between "stopping tangential acceleration" and "stopping radial expansion". The former can drop off to near zero without stopping the latter.
     
    Last edited: May 9, 2010
  10. May 9, 2010 #9
    Dave you raise some good questions. How would we within the Universe know about "special points" along the axis, especially if our relativistic point is outside the universe?

    If it is not possible to locate the "special points" then no violation of relativity.

    Krombacher
     
  11. May 9, 2010 #10
    Dave, with regard to rigid disk. If the singularity of the big bang was rotating, then it follows that everything blowing out of the rotating big bang is also rotating, like a rigid disk. If not like a rigid disk, then we would KNOW for sure whether the universe was rotating, because we would see some parts of it moving at different rates than other parts.

    But we don't know because if the whole thing is turning, how could you know? But you are on track with the rigid disk concept, as it was my analogy to a record or CD playing.

    The more the "rigid disk" expands the faster any "sticker" on the edge of the disk moves relative to a sticker towards the center of that "rigid disk". So the "rigid disk" can only expand so much, because anything on its edge will move faster and faster, but limited by c, and hence limited in expansion.

    Krombacher
     
  12. May 9, 2010 #11

    DaveC426913

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    I must away to bed.

    Read up on rotating universe and, if not entirely satisfied, you will at least have a fresh set of questions for tomorrow.
     
  13. May 9, 2010 #12
    Good night Dave,

    I read some on rotating universe, but didn't see anything remotely to what I am trying to convey. Feel free to point to any discussions or threads on this board regarding what I am saying, and I will be very pleased to read it.

    Krombacher
     
  14. May 9, 2010 #13

    DaveC426913

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    Please, stop saying this.

    It is a conclusion based on incorrect premises. Get the premises correct (by reading and by asking more questions) before drawing false conclusions.
     
  15. May 9, 2010 #14
    You said:

    "Please, stop saying this.

    It is a conclusion based on incorrect premises. Get the premises correct (by reading and by asking more questions) before drawing false conclusions."

    Are you saying that the premise of a rigid disc is incorrect?

    Krombacher
     
  16. May 9, 2010 #15

    DaveC426913

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    You shouldn't be looking for things like what you are trying to convey. You should be looking to learn the things that are not what you think.

    If a student thought 2+2=5, and then went looking in a book for confirmation, but the book only ever said 2+2=4, well what does the student learn about his belief?

    Most of the premises you've started with are incorrect. It is much faster for you to read than for someone on PF to correct each premise individually.
     
  17. May 9, 2010 #16
    Alright, let's say we don't have a rigid disk, but we have a whirlpool as Dave suggests. Therefore the universe at the very edge is trying to slow down as the rotating universe expands, according to Dave.

    Let's compromise and say that we are spinning pizza dough over our head. If Dave is right, the edge of the pizza is trying to slow down so as not to violate tangential c as I try to expand the pizza dough into a larger circle. The pizza dough would definitely "tear" near the edge, wouldn't it, effectively stopping the expansion. And hence my point.

    Krombacher
     
  18. May 9, 2010 #17

    sylas

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    There's nothing to "tear". It is more like water, as Dave has already said. Furthermore, you have to bear in mind that speed limits of c really only apply locally. The current expansion already has galaxies receding from each other at significantly greater than "c", in the sense that the "proper distance" between then is increasing much more than the speed of light.

    As Dave says, the best bet is to read up on rotating universe models. The famous pure mathematician Kurt Godel turned his hand to looking at this problem rigourously. I don't know a great deal about it myself, but a reference is:
    • Rotating Universes in General Relativity Theory, Kurt Godel, in General Relativity and Gravitation, Volume 32, Number 7 / July, 2000, pp 1419-1427, doi:10.1023/A:1001911308752
      Reprinted from Proceedings of the International Congress of Mathematicians, Cambridge, Mass. 1952, vol.1, p.175.

    Cheers -- sylas
     
  19. May 9, 2010 #18
    sylas, thank you! Very interesting. I was not aware of the fact that "current expansion already has galaxies receding from each other at significantly greater than "c", in the sense that the "proper distance" between then is increasing much more than the speed of light".

    If true, then that certainly is a game changer as far as putting a cap on expansion (my thought experiment). Are the galaxies receding from each other at speeds greater than c due to the expansion of the universe (i.e. big bang momentum) or due to gravity effects?

    I think it must be due to gravity effects and here's why I think that.

    1) We know that entropy must increase with the forward movement of time. Another way to put this is to say that time must move forward with increases in entropy.

    For example, if a glass of water fell off of a table and shattered in a bunch of pieces, time is moving forward as more entropy is created. However if suddenly those pieces came together and jumped on the table, it would appear as though we are watching a video being rewound, or it would appear as though time is moving backward as there is less entropy.

    That's why I think that the Universe may never contract, because if it did, there would be less entropy, and hence a contracting Universe would be going backwards into time (a no-no, if we are to avoid paradoxes).

    So what I am trying to achieve is to have a Universe that can neither contract and also hit a limit to expansion.

    2) We are also learning that gravity is an attempt by phyical forces to increase entropy in the Universe such that by masses interacting with one another vis. a vis. gravity, they are able to create more disorder, and hence move forward in time.

    Here's the link:

    http://www.technologyreview.com/blog/arxiv/24975/


    So. We know that time slows as you approach c. We also know that if you exceed c, an impossibility, then time would move backward (and hence make it possible for paradoxes, and that's why it's impossible to move faster than c)...UNLESS

    you can increase entropy. Increasing entropy must mean that you are moving forward in time and not backward.

    So my thought is that if the galaxies are moving away from each other faster than "c" then they must be creating so much entropy to offset the backward movement of time.

    I wonder if entropy is being increased at such fast rates that that allows for phenomena faster than "c".

    That's what ultimately will allow us humans to travel large distances in faster than c times frames...we will have to create massive disorder (entropy) as we do it so that we don't accidentally slip backward into time (an impossibility).

    Krombacher
     
  20. May 9, 2010 #19
    I think what it all boils down to is :

    We know that time links the two major laws. The law of entropy - time moves forward as entropy increases, and as entropy increased time moves forward. And the law of c - nothing may go faster than the speed of light and so time slows as you approach the speed of light.

    These two laws lead to a third law - nothing of mass may go back into time, or paradoxes will result.

    We are learning that gravity plays a role in both laws as well. Gravity as an interaction between masses to increase entropy and gravity as a means of motion and hence velocity not to exceed c.

    What is interesting is which of the two laws is stronger? I.e. if we pitted the law of entropy against the law of c, which would win?

    My guess is that the law of entropy would win. In other words, you may go faster than "c" if you are creating immense disorder as you do it.

    But if entropy is that strong of a law, then there can be no contracting Universe, as that would create more order not disorder.

    The question for me though is, is the law of c strong enough to also stop expansion of the Universe, via my thought experiment of my very first post?

    Krombacher
     
  21. May 9, 2010 #20

    DaveC426913

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    This is cosmology 101.

    Don't you think you should be reading up on the facts before drawing conclusions?

    It isn't.
    No.


    No.

    No.

    trying to achieve

    You are attempting to build your own theory. This is expressly forbidden on PF. You agreed to these rules when you signed up.

    Thread reported for violation.

    A last word before th is thread is locked:

    There is nothing wrong with an inquisitive mind; we welcome and encourage this. But rather than making claims, you must ask questions. Your misconceptions can then be corrected beforfe they spin so wildly out of control.
     
    Last edited: May 9, 2010
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