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Cosmic Relativity

  1. Aug 24, 2010 #1

    mysearch

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    I was wondering if anybody knows the status of the work of C. S. Unnikrishnan in respect to a paper he wrote entitled http://arxiv.org/PS_cache/gr-qc/pdf/0406/0406023v1.pdf" [Broken].

    Extract taken from the abstract:
    “In this paper I argue for a reassessment of special relativity. The fundamental theory of relativity applicable in this Universe has to be consistent with the existence of the massive Universe, and with the effects of its gravitational interaction on local physics. A reanalysis of the situation suggests that all relativistic effects that are presently attributed to kinematics of relative motion in flat space-time are in fact gravitational effects of the nearly homogeneous and isotropic Universe.”

    C. S. Unnikrishnan is an associate professor at the http://www.tifr.res.in/" [Broken] might give those with the necessary background in this subject a more immediate insight to the scope of his work.

    Extract taken from last page:
    “Consider two clocks in a laboratory that are moving very fast inertially. Then one of the clocks, B, is transferred to another laboratory that decelerates and stops, say relative to the reference markers provided by the distant stars or the CMBR. (A) proceeds along its inertial motion. Finally B accelerates again such that it comes to rest relative to A. In the special relativistic analysis of this problem, it is the accelerated clock B that ages less, since the physical situation in a space-time diagram from A’s frame is identical to that in the original twin paradox."

    In this introduction, he seems to raise some fairly reasonable questions about the twin paradox in respect to Einstein’s first explanation back in 1918 plus the subsequent spread of interpretations based on accelerated frames, lines of simultaneity and time encoded light beams etc.
     
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  3. Aug 24, 2010 #2

    mysearch

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    It would appear that the ‘Beyond the Standard Model’ sub-forum feels this is a mainstream relativity discussion as they have moved this thread back here.:confused:
     
  4. Aug 24, 2010 #3
    Wasn't GR developed to address this? Looks as if this approach ignored GR altogether.
     
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  5. Aug 24, 2010 #4
    I think the author of that paper has taken the Ether of Lorentz Ether Theory, which is compatible with Special Relativity and then defined the absolute rest frame of the Ether as being where the CMBR is isotropic. There might be some small merit in such an approach (if we ignore the fact that two observers separated by cosmic distances that both consider themselves to be at rest wrt the CMBR are not at rest wrt each other), but unfortunately he has got his analysis wrong and arrived at the wrong conclusions. He has got so much wrong in that paper, that I do not know where to start debunking it. It just goes to show that even well qualified people can get confused by the twins paradox which might be a comfort to the rest of us.
     
  6. Aug 24, 2010 #5

    ZapperZ

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    The "Beyond The Standard Model" deals with extension beyond what is the current Standard Model of elementary particles. Your post has more to do with someone who has a different idea than Special and General Relativity, not with elementary particles. It has nothing to do with this being "mainstream".

    BTW, while we're on the subject, I would strongly suggest that you wait till this is published before investing in such effort to see if this even matters. If you have a reference to where this was published, please provide such information.

    Zz.
     
  7. Aug 24, 2010 #6

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    Thanks for the clarification. I saw the synopsis of this sub-forum described as “Professionally researched theories” and thought this applied in this case.
    I assume you have some qualification to the word ‘published’ that I might not fully appreciate. The only reference I have is `arXiv:gr-qc/0406023v1:7 Jun 2004’ that I have the feeling you are going to tell me doesn’t count. I presume by the date (2004) suggests this paper has had enough time to attract attention if it were going to do so? Other references are in my first post.
    Kev, I know you have been looking at this subject for some time. While your focus and priority might be on other things, I would appreciate any summary of the main points, which you think are fundamentally flawed. Thanks

    While the indication seems to be that this idea doesn't fly, I would appreciate any further clarification of specific problems that any other PF members might be able to highlight providing this is OK with the PF guidelines. Thanks
     
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  8. Aug 24, 2010 #7

    ZapperZ

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    "published" means appearing in a peer-reviewed journal. We have a set list of accepted journals listed in the PF Rules thread. Appearing on arXiv does not qualify, because these do not undergo such review. While high energy physics and string/quantum gravity issues are often done on arXiv, other subject areas are still heavily dependent on articles that have passed peer-reviewed. Thus, we strongly urge that sources must be published before they are used.

    The manuscript on arXiv appeared in 2004. If I were you, I would be very suspicious if, after all that time, it hasn't made it into any journal. All the warning bells and whistles should go off on something like that.

    Zz.
     
  9. Aug 24, 2010 #8

    Ich

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  10. Aug 24, 2010 #9

    AWA

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    For starters the author claims that there is "absolute time" (wich in itself is against the very principle of relativity) and at the same time that GR follows naturally from his theory. This contradiction makes it more than highly suspicious. Either he understands very little about relativty or he is trying to disguise as relativity something that clearly is wrong and misleading.
     
  11. Aug 24, 2010 #10

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    Ich - many thanks - a pretty damning account by the sounds of it.
    I came across Unnikrishnan’s work via this paper, which then references ‘Cosmic Relativity’. In this paper, it cites that Einstein got around to addressing the Twin Paradox in 1918, although it was originally raised around 1911. It suggests that Einstein used aspects of GR to address the problem, which many sources now appear to reject as unnecessary. However, for a relativity novice like me, there appears to be some confusion about which interpretation is now thought to be the accepted resolution of the paradox, e.g.

    1. Einstein GR based description
    2. Acceleration sufficiently identifies the moving frame, then apply Lorentz transforms
    3. Lines of simultaneity allow time in each frame to be compared
    4. Exchanging time encoded light signals that account for propagation delay
    5. All of the above
    So would appreciate a pointer to any specific source/description that is considered to be the definitive position. Many thanks again.
     
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  12. Aug 24, 2010 #11

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    To be honest, I was deferring reading the paper in detail until I got some sort of acceptance from PF members who know more about this subject. Kev raised the issue of the absolute rest frame in #4, although the author switches between preferred, rest and absolute at various points. I believe he might be making these statements based on his assumption that CMB is a ‘preferred’ frame, not necessarily absolute, but because the expansion of the universe is very slow – see figure on page 2, then it is for all practical purposes absolute. I am not arguing his case, simply trying to understand the possible logic. Absolute time is mentioned as the following quote suggests:

    “But we know for a fact that there is a preferred frame, and also absolute time. The frame in which the Cosmic Microwave Background Radiation (CMBR) has no dipole anisotropy is the absolute rest frame, and the value of the monotonically changing temperature provides the absolute time”

    Presumably, somebody is in a position to say whether this is another false statement.
    Thanks
     
  13. Aug 24, 2010 #12
    Hopefully I can come back to this in more detail later, but briefly the answer is 5. There is no single resolution and as long as the numerical predictions of the various resolutions when correctly interpreted and applied are the same there is no way to eliminate competing resolutions. Philosophically I find the pseudo gravitational GR explanation the least satisfactory. It requires that I spend my life stationary and whenever I accelerate, for example by stepping on the accelerator of my car, that a gravitational field coincidentally springs up and accelerates the ENTIRE universe in the opposite direction while I remain stationary. I cannot prove that does not actually happen so that explanation cannot be eliminated, but it is extremely unlikely and very egocentric and it cannot be true for everyone. However, physics is not about philosophy and if the math works and if you cannot find a contradiction that is physically measurable, then you have to accept the predictions! I do not think Einstein actually meant that the entire universe actually accelerates in the opposite direction each time you step on the gas, but by the equivalence principle, the predictions are the same as what would be measured if that actually happened!

    Here are some comments on brief extracts from Unnikrishnan's paper http://www.ias.ac.in/currsci/dec252005/2009.pdf :
    This is simply wrong. The analysis for the case where the two twins both initially have high speed motion has been analysed in this forum several times and the answers are compatible with experimental results.

    Unnikrishnan obviously misses the point that I can pick an observer that is not at rest with the CMBR and come to exactly the same conclusions about the relative ageing of the the twins, disproving his claim that the CMBR is the preferred frame.

    Eddington calls the reversal of the velocity as occurring by "supernatural means" because it requires that the entire universe is accelerated. Unnikrishnan obviously does not get this.
    Einstein's "GR" explanation of the twins paradox does not mean that Einstein acknowledges that the SR explanations are inadequate. All the non acceleration resolutions had already been advanced and accepted by people that understood relativity and there would be no point in Einstein simply repeating the explanations that were already in the public domain that were not accepted by die hard anti-relativists. Simply repeating the known resolutions is not going to suddenly make the the anti relativists suddenly understand them, so Einstein came up with another approach, that validated (rather than disproved) the non acceleration SR approaches, because the predictions are in agreement.
     
  14. Aug 24, 2010 #13
    In addition to kev's response, I would point out that the above resolutions are substantively just variations on a single "theme". The difference between them is procedural, the reason for the differential aging is the same in each of them.
     
  15. Aug 24, 2010 #14
    LOL. I think Einstein's intent was that considering yourself stationary for the above is allowed, but not required. Like you pointed out, he wasn't contradicting other resolutions, he was just filling in a gap.

    The exact same scenario of the entire universe accelerating due to pseudo-forces while an observer is "stationary" in an accelerated reference frame is perfectly valid (and commonly used) in Newtonian physics, which I assume is the reason Einstein considered it an important gap to fill.
     
  16. Aug 25, 2010 #15

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    Kev, first and foremost, thanks for taking the trouble to point out some of the key problems within the Unnikrishnan paper. Second, I accept that people have been looking at this problem for 100 years and, as such, I assume that virtually very scenario that can be dreamt up has been discussed and presumably resolved. However, this doesn’t stop a novice like me from trying to resolve the apparent ‘paradox’ in their own mind. Of course, with so much conflicting data available these days, it is easy to get side-tracked onto the wrong path. Therefore, my comments below are primarily focused on the remaining issues that I am trying to resolve.
    Let me initially make reference to the following paper, which seems to advocate a more strict approach to what is and what isn’t the cause of the paradox – see page 3; bullets (a-d): http://home.sprynet.com/~owl1/twinparadox.pdf" [Broken]

    Initially, I had resolved the twin paradox based on the simplistic assumption that the space-twin would feel the force of acceleration [F=ma] and therefore this identified the relative moving twin. As such, this identified the frame to which the Lorentz time dilation transform applied. However, other papers then suggested weaknesses in this argument by substituting the space-twin with a relay handover that maintained constant velocity throughout. In addition, the wider implications of the Earth moving within the solar system, the solar system within the galaxy and the galaxy within the universe, and so on, suggested that my original model might be too localised.
    If possible, can you point to any reference that expands on this explanation? I must admit, I thought that referring to CMB as a preferred, not absolute, frame was not necessarily invalid; especially if you ignored the actual expansion of the universe within a local area of spacetime.
    Again, on first reading, this model seemed to suggest a reversal of the standard twin paradox, which would also lead to a reversal of which twin experienced time dilation. Again, I would appreciate any links to the discussions that resolves this particular case.
    On a tangential note, while I agree that physics is not philosophy, I do not think that mathematics in isolation is verification. There are aspects of modern physics that now exceeded our ability to physically verify and therefore physics has to continually assess, and identify, where the limits of inference might have been exceeded. However, returning to more solid ground, I also tried to adapt the original twin model to become a ‘triplet’ model, sorry :eek:, in which two of the siblings went into space on an identical journey, but in opposite directions. I won’t repeat the details here, but an outline can be referenced in the following thread: https://www.physicsforums.com/showthread.php?p=2850785#post2850785"

    Fredrik comments in post #2 steered me towards considering spacetime diagrams and lines of simultaneity, which while informative, still left questions about the correlation of time in the 2 identical moving frames. For example, the diagram attached to post #6, in the thread referenced above, seems to support the idea that the 2 siblings are the same age when they return to Earth, and at various points on route, while the lines of simultaneity seem to suggest that both are younger or older at other points on the trip.

    There was one other point in the initial Unnikrishnan's paper: http://www.ias.ac.in/currsci/dec252005/2009.pdf" - see section ‘Counter-examples’ where he discusses stopping clocks on route to ascertain a comparative judgement of time. With respect to my example above, if the 2 siblings above took 100’s of atomic clocks on their respective journeys, and stopped them at designated distances on route, could these clocks be compared at the end of the journey and would they show time to be synchronous throughout both journey despite the implications of the lines of simultaneity?
     
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  17. Aug 25, 2010 #16

    jtbell

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    If you want to focus on the twin paradox, you might want to start a new thread instead of staying in one called "Cosmic Relativity" which some people are probably ignoring after the first few posts.
     
  18. Aug 25, 2010 #17
    While that paper may be correct in addressing what everybody knows, that a solution to the paradox can be reached via SR alone, it is totally wrong in its rejection of the other solutions and as Kev and Al68 said all of your listed solutions are valid and amount to the same thing.
     
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  19. Aug 25, 2010 #18
    The standard twins paradox resolutions resolve the case in which both twins start in inertial motion with the relative velocity between them equal to zero, their initial velocity relative to the CMBR or anything else makes no difference to the result, so is not normally specified at all in standard resolutions.

    The reason the standard resolutions don't specify an initial velocity of the twins relative to the CMBR or something else isn't because it's zero, it's because there is no reason to specify a value that the calculations don't use.
     
  20. Aug 25, 2010 #19
    Unnikrishnan's papers on relativity are terrible, you are wasting your time reading (and citing) them. He lacks a basic understanding of relativity which puts him in the fringe category. You can safely ignore his papers.BTW, Subask Kak is even worse.
     
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