Gravitational Time Dilation

Discussion in 'Astronomy, Exobiology, & Cosmology' started by RajeshTrivedi, May 4, 2015.

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  1. OnlyMe Valued Senior Member

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    Here is the sequence of posts that led to the post you were just responding to.

    My post,
    The two imediately preceding. You could also follow the links back, but then ....

    The issue was and is whether Gravity is self gravitating! No matter how anyone chooses to argue to question one way or the other. As Q-reeus pointed out you dredged up the old debate, even if you forgot what it was about.

    Edit to add, BTW the reason I started with the selective recall comment is that I have also questioned the idea that Gravity is self gravitating.., and in discussions that you were a party to.
     
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  3. paddoboy Valued Senior Member

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    Gravity is self gravitating certainly, and that is exactly what the following means......
    Certainly not what you originally claimed thus........
    The debate never touched on any absence of a central mass. It was purely and simply the uncluttered fact that gravity/spacetime being non linear, means that gravity makes gravity, and supported by references and tashja's Professors.

    Yep, I dredged up an old debate to make a point and show professional references, so? Nothing more, nothing less.
    Did you? That's nice, I must have forgotten.
    Do you have any reference saying gravity is non linear?

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    Last edited: Jun 3, 2015
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  5. paddoboy Valued Senior Member

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    http://www.cco.caltech.edu/~kip/ftp/ScheelThorneUFN130110.pdf

    Geometrodynamics: The Nonlinear Dynamics of Curved Spacetime

    Mark A. Scheel1 and Kip S. Thorne1 1Theoretical Astrophysics 350-17, California Institute of Technology, Pasadena, CA 91125, USA (Dated: January 9, 2014)

    We review discoveries in the nonlinear dynamics of curved spacetime, largely made possible by numerical solutions of Einstein’s equations. We discuss critical phenomena and self-similarity in gravitational collapse, the behavior of spacetime curvature near singularities, the instability of black strings in 5 spacetime dimensions, and the collision of four-dimensional black holes. We also discuss the prospects for further discoveries in geometrodynamics via observation of gravitational waves.
     
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  7. paddoboy Valued Senior Member

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    Well put brucep!
    Actually a link I supplied also in the old thread I recollect.
     
    Last edited: Jun 3, 2015
  8. OnlyMe Valued Senior Member

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    First, no one has proven that gravity is nonlinear or that gravity is self gravitating. Even understanding that the term self gravitating may have different meanings in different contexts. What is discussed is that GR is nonlinear, or more accurately, in your reference above, the nonlinear dynamics of curved spacetime is being evaluated.

    From the conclusion of the paper your quoted.

    VII. CONCLUSIONS
    Physicists have barely scratched the surface of geometrodynamics. As numerical simulations continue to improve and are used to explore more complicated and generic situations, we expect to learn more about the geometrodynamics of critical behavior, singularities, dynamical black holes, and other phenomena. We look forward to observations of gravitational waves from strongly gravitating astrophysical sources, which will enable usto test the geometrodynamical predictions of Einstein’sequations for the first time.

    The above is just as theoretical as some of what you have been railing against of late. In a strict since it is not science, it is theoretical speculation. Nothing real is being observed, tested or even described... GR is still theory.

    Without falling back on some quote, it is sometimes unclear you understand, just what do you think self gravitating means? In your own words if you can.

    Yes, gravitational fields of two or more massive objects can and do interact such that the local gravitational field could not be described by the gravitation associated with either massive object, by itself... But as I said there is no evidence that anyone has ever observed any gravitational field that is self gravitating. The idea is speculation based on a conceptual interpretation of the field equations, not something that is or has been observed and is then being described.
     
  9. paddoboy Valued Senior Member

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    Of course it is theoretical, no one said it wasn't, difference being it is not trying to over throw an established incumbent theory on a science forum of all places.
    On that score, my railing will continue.
    GR certainly is still a theory, a theory that is overwhelmingly supported by most and deservedly so, and almost certainly will not be replaced by someone railing against it on any science forum.
     
  10. paddoboy Valued Senior Member

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    I would also add to the ire of some, that GR and SR are in the near certain concept of scientific theories, and have no peer with regards to theories of gravity.
     
  11. Q-reeus Valued Senior Member

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    Doubly wrong. Firstly, Farsight's often repeated position is exactly yours re 'gravity gravitates'. How does that make him supporting me? Wake up - idiot! Your memory is evidently poor, and this is not the first time I have needed to 'refresh it'. Further, I had two experts that outright supported my position, and a third who had to concede my point but in a 'delicate and diplomatic way' - the same one who's site is linked to in #540 here. And all that can be found in links leading to older links, according to what I gave in #527.

    The pro 'gravity gravitates' offered no explanation as to how in EFE's all vacuum solutions have precisely zero Ricci curvature. Instead, merely asserted that e.g. GW's (once again - never detected, only inferred) 'self' gravitate', or that 'eternal BH's' are a 'pure self-sustaining field'. Go read again the last para in #527 here. All is not well in 'consensus' GR.
    Fact is, as you are nothing more than an inveterate quote-mongering cheer-leader for only sometimes majority/consensus opinions and pronouncements, of 'authorities', you are totally incapable of directly challenging my position as per e.g. #527 this thread, or #332 here:
    http://www.sciforums.com/threads/black-hole-not-so-black.142702/page-17
     
    Last edited: Jun 3, 2015
  12. paddoboy Valued Senior Member

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    Take it easy fella.....
    If I have forgotten or otherwise it certainly does not detract from the real effects of gravity making gravity as a result of its property of nonlinearity.
    And no you did not have any known experts supporting your position.
    Post 540 and the link therein supports my position and not yours.
    from that post.....
    The upshot? We should be careful applying pre-gr terms to general relativity. Personally, I find "gravity gravitates" a useful way of picturing the non-linearity - as long it doesn't mislead one into thinking that the "gravitational energy" is just a localizable source term like any other.
    But just as with most of our troubled alternative people, you seem somewhat delusional and rather emotional to boot.
    My advice, other than categorically telling you that nonlinearity and gravity making gravity are real effects, is to remind you that all the hot air and bluster you attempt to use to give your view at least an ounce of credibility, is to no avail.
    Now again, really take it easy for your own well being and good.
     
  13. Q-reeus Valued Senior Member

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    Poor memory is one thing. Outright lying is another. Both Sascha Vongher and Peter Donis outright supported my position - though in Sascha's case it took me quite some time to fully realize what he meant. For instance 'you might as well say nothing gravitates' seemed inscrutable at the time, but in retrospect, it was just his way of saying spacetime curvature has the same gravitational 'mass' as uncurved spacetime. Thus completely consistent with his earlier direct statements.
    Actually, you are simply not conceding my position that bolded part is indeed a diplomatic and cautious statement - "a useful way of picturing" was in response to my pointing out what in-vacuo zero Ricci curvature directly implies - 'gravity does NOT gravitate' - according to EFE's. It is futile to continue arguing this with an imbecile not capable of appreciating anything mathematical. Lacking the capacity for a healthy sense of shame or humility - much like a psychopath experiences no remorse after murdering.
     
  14. RajeshTrivedi Valued Senior Member

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    Admirable for Paddoboy !! for other counter participants its like getting fooled !!

    Paddoboy with no fundamental knowledge of the subject, beyond lay science journal knowledge, is taking on almost all the guys on substantial complex issues.......I am getting speechless. Its not worth engaging Paddo beyond silly pranks, but yes as someone said, sometimes his links may provide some valuable information. No prudent person can win Paddoboy on argument, he changes and changes smoothly giving no chance to others.

    All those who wish to understand this Gravity Gravitating itself, should also acquaint with the alternative (or some modification of GR equations) by Huseyin Yilmaz. It requires somewhat mathematical approach and its a bit alternative improvisation to GR, so obviously our friend will oppose this tooth and nail without understanding the abc of it.
     
  15. RajeshTrivedi Valued Senior Member

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    Thats a good realization, better late than never. No prudent man can ever win an argument with him.
     
  16. paddoboy Valued Senior Member

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    No the lie is none of the professors supported your position in total, a couple did support mine in total.
    Gravity does gravitate in the following sense. If we have a mass, for instance a stone, we say that it 'gravitates' meaning two things: (1) the first is that it falls attracted by another mass (like the Earth) and (2) the second is that itself attracts masses. Now let's see if gravity itself does the same. To see this, we can consider a small localised pulse of gravitational waves. This is a 'thing' which is entirely made of gravity: there is no matter whatsoever, it is only a local deformation of spacetime, namely gravity. Well, we can ask if such localised pulse of gravitational waves does or does not gravitate. According to what we said before, we can say that 'it gravitates' if (1) it falls attracted by a mass and (2) it attracts, in turn, masses. Now, according to the equations of general relativity, both things happen: a small pulse of gravitational waves 'falls' towards a mass (for the same reason light does), and itself deforms spacetime around itself, and therefore attracts any other masses. In this sense, 'gravity gravitates'. Perhaps there is a different sense in which 'gravity does not gravitate', but I am not aware of it, and could not guess it.

    Carlo Rovelli



    The science on whether empty space expands (as predicted by *gravity* theory) or gravitational waves propagate through “empty” space, or GR’s “self-interacting” nonlinearity for example, are not in question. Are suchlike phenomena “gravity in GR gravitating”? I refuse discussing verification transcendent distinctions. You must make up your own mind about what you mean by “gravity in GR” and “gravitating”. Intrinsically curved space-time? Then see whether you can live with further language preferences that would make “curved space-time does curve space-time” or suchlike acceptable to you, whether it ‘means what you meant to say’. You may as well defend that nothing gravitates, because with space-time as a given, there is no further time to do anything anyways – after all, “there is no gravity in GR” but just self-consistent geometry.

    S


    -----------------------------------------------
    Dr. Sascha Vongehr


    But even in the vacuum (no matter) one can have gravitational fields (eg black holes). Ie, the gravitational field can feed on itself. As Wheeler argued and showed in the 60s one could have geon-- a concentration of gravity waves which are more or less trapped by their own gravitational field, so that from outside it just looks like a mass but inside there is no matter at all.

    Furthermore, the mass of a body consists both of the sum of the energy of the
    matter plus a contribution from the gravitational field. Ie, yes, gravity
    gravitates.

    William G. Unruh

    """""""""""""""""""""""""""""""""""""""""""""""""""""""

    Ok qreeus, perhaps if you carried on with less of the whinging, less whining, less complaining, and calmed down a bit, you would see that yep, as I have been saying from day one...gravity gravitates due to the property of nonlinearity.
    [psst, I see rajesh is here to give you some support. That should be fun!

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  17. RajeshTrivedi Valued Senior Member

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    Its quite evident that both Paddoboy and Brucep do not understand the meaning of Gravity gravitates itself and non linearity of gravity. What they have understood and wish to convey is that Gravity produces further Gravity....thats perfect nonsense....

    Non linearity of Gravity simply stems from the fact that EFEs are non linear equations, so its difficult to solve them exact without analytical and numerical solutions for multi body system, this is not a failure of GR as such, but makes it quite complex. Due to this it can be simply said that the effect cannot be superimposed, that is impact of m1 (or E1) at P and impact of m2 (or E2) at P cannot be added, thats the non linearity. This aspect and the effect of a remote other source (since there is no provision in GR directly to add up another source in the EFEs) on local point is taken as Gravity Gravitates.....a nice word coined, but it does not mean that Gravity produces Gravity as Paddoboy is latched on.
     
  18. paddoboy Valued Senior Member

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    You have a couple of unanswered questions Rajesh....
    Now if you are so sure you are correct in any claim you have made, all I ask for is one supporting expert opinion or reputable link.
    I mean you don't expect the forum to take the word of an Electrician who fits a few light bulbs now and then, over more expert opinion, now do you?

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  19. paddoboy Valued Senior Member

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    No, you couldn't be more wrong.
    And I have given reputable links backing that up.
    For instance, how do you expect any BH to hold its shape, as no signal can ever get from where the mass is [Singularity/quantum/Planck level] back out to the EH.
    http://www.einstein-online.info/spotlights/gravity_of_gravity
    The gravity of gravity
    One reason why the physics of general relativity is much more difficult than that of Newton's theory of gravity or the theory of electrodynamicsis a property called non-linearity. In short, gravity can beget further gravity - where gravitational systems are concerned, the whole is not the sum of its parts.

    massessuch as planets or stars. In front of us, there is a sphere drifting in space. We can chart the gravitational influence which this sphere exerts on other masses in its vicinity (in physics-speak, the sphere's gravitational field) by keeping a record of its influence on a small test particle. The particle's mass is so little that its presence does not significantly alter the situation. Thus, we can use the particle as a probe - we keep track of the force exerted by the spherical mass as we move the particle to different locations.

    As an example, say that when our test particle is at location A, the gravitational force pulling it towards the sphere has a magnitude of twoNewton. Here is a sketch showing the sphere on the right at the location M1 and the test particle on the left at location A. The force on the test particle is represented by the blue arrow - the arrow's direction shows the direction of the force (an attractive force, so the arrow points towards the sphere) and its length represents the magnitude of the force (in this case two Newton - twice as long as the reference length representing one Newton, shown on the bottom left):
     
  20. RajeshTrivedi Valued Senior Member

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    Although I do not do that as you will not be able to understand the difference between an electrician and an electrical engineer. Nonetheless do you think it is demeaning or lesser to be an electrician ?? F0r that matter did I ever tell you that you are a retired mechanic so you must be a fool ? I am just saying that you are admittedly unaware of Physics / maths at the deeper level, still you are able to engage almost all the guys who have better and deeper understanding of the subject.

    PS : You are able to engage Paddoboy, because people here who are giving alternative ideas or even trying to put forth the correct position, want their alternatives to be seen, they are checking, and they do not want falsehood or incorrect position to remain on record.
     
  21. paddoboy Valued Senior Member

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    All you need do is show one reputable link that fully supports what you say.

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    Cat got your tongue?
     
  22. paddoboy Valued Senior Member

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    And I'm saying, and showing, and referencing what I say, that what I claim is generally factual...and far removed from your anti BH/GR fairy tales which only exist within your mind..
     
  23. Daecon Kiwi fruit Valued Senior Member

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    If energy is equivalent to mass, and mass produces gravity, is gravitational force not a form of energy?
     
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