Speed of gravity
in [Relativity]
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From: BURT on 4 Mar 2010 14:48 On Mar 4, 11:09 am, "Juan R." González-Álvarez <nowh...(a)canonicalscience.com> wrote: > G. L. Bradford wrote on Thu, 04 Mar 2010 11:24:21 -0500: > > > > > > > "Juan R. González-Álvarez" <nowh...(a)canonicalscience.com> wrote in > > messagenews:pan.2010.03.04.11.32.22(a)canonicalscience.com... > >> carlip-nospam wrote on Mon, 01 Mar 2010 17:53:55 +0000: > > >>> Art <n...(a)zilch.com> wrote: > >>>> Has this question been settled yet? I've read that Einstein assumed > >>>> gravity travels at c. But I've also read that certain orbits are > >>>> iunstable unless gravity travels >> c. > > >>> It depends what you mean by "settled." > > >>> General relativity predicts that gravity propagates at the speed of > >>> light, in the sense that if you change the matter configuration in > >>> some finite region, the gravitational effects of that change don't > >>> reach distant regions until after the light-travel time to those > >>> regions. I wouldn't say Einstein "assumed" this -- it was not put > >>> into the derivation of the field equations of general relativity, but > >>> is, rather, a conclusion. There's a rigorous proof in Low, "Speed > >>> limits in general relativity," Class. Quant. Grav. 16 (1999) 543, on > >>> line at arxiv.org/abs/gr-qc/9812067. > > >> Right. > > >>> It's also true that if you start with *Newtonian* gravity and stick in > >>> a finite propagation speed, orbits become dramatically unstable. > > >> Newtonian gravity is not a theory of "finite propagation speed" [1]. > > >>> This does > >>> *not* happen in general relativity, though; in GR, there are > >>> additional velocity-dependent interactions that almost (but not quite) > >>> cancel the instability. > > >> Adds self-interaction, retardation, or many-body effects and the GR > >> 'orbits' > >> become highly unstable. > > >> Numerical relativists have never checked the general case of motion. > > >> Authors as Dr. Schieve "regarded as one of the world experts in the > >> field of relativistic chaos" [2] know that GR fails for general case in > >> many-body > >> dynamics and they are using other theories of gravity to try to study > >> those > >> more complex motions [1] for which, I repeat, GR fails. > > >>> The lack of exact cancellation leads to slow changes in the orbits of > >>> binary neutron stars ("gravitational radiation reaction"), which are > >>> observed and agree very precisely with prediction. This cancellation > >>> was, again, not put into the derivation of the field equations of > >>> general relativity, but comes out as a conclusion. It's discussed in > >>> my paper, "Aberration and the speed of gravity," published in Phys. > >>> Lett. A267 (2000) 81, on line at arxiv.org/abs/gr-qc/9909087. > > >> This paper only considers simplified models, only studies some aspects > >> of motion and make several bold claims about Newtonian gravity and > >> other models > >> that the author clearly dislike [1]. > > >>> As for the experimental/observational question, we have no direct > >>> evidence. Gravity is too weak an interaction for the difference > >>> between an infinite propagation speed and the GR prediction of a > >>> finite speed plus velocity-dependent interactions. But a Newtonian > >>> theory with infinite propagation speed would give the wrong results > >>> for binary pulsars, unless some additional radiation reaction terms > >>> were stuck in by hand. > > >> Continue doing bold claims about Newtonian theory. In particular > >> Newtonian theory is not the c--> oo limit of a field, metric, or > >> similar theory. This limit gives you a theory of gravity without > >> retardation, which is not equivalent to a true AAAD theory, of course > >> [1]. > > >> Evidently, nobody would try to use a Newtonian theory (non-relativistic > >> theory) to explain a relativistic observation. One would use a > >> generalized theory, which already gives the "radiation reaction terms" > >> from first principles. > > >>> It's also worth noting that the same issue occurs in electromagnetism.. > >>> Almost everyone accepts that the electromagnetic force travels at the > >>> speed of light. > > >> You continue doing very bold claims Steve. > > >> The Lorentzian electromagnetic force (associated to the field model of > >> electromagnetic interactions) "travels at the speed of light". But that > >> is not true in more advanced models of electromagnetism. > > >> E.g. the generalized electromagnetic forces obtained from the theory > >> studied by Dr. Schieve and many other people to study relativistic > >> chaos, dissipation, and other advanced topics are instantaneous and > >> cannot be obtained from electromagnetic field theory, which (as is > >> well-known to actual experts) gives the wrong results [3]. > > >> There exists a quote from Schieve monograph "Classical Relativistic > >> Many-Body Dynamics" [3] which is reproduced in [4] about the failure of > >> field theory: > > >> "Of course, the most interesting results derivable from the many-body > >> theory are for systems for which field theory is not capable of > >> producing the equations of motion." > > >> In [4] it is showed that the theory discussed in the above monograph > >> reduces exactly to Newtonian theory plus Coulomb interactions, whereas > >> Maxwell-Lorentz fails. [4] also discusses some of the mistakes in your > >> wrong PLA paper. > > > ============================= > > > Just for the heck of it, too bad you did not mention the Lagrange > > (...) > > My goal was not to write a detailed post naming all the mistakes and > over-simplifications that Steve is doing :-D > > In the several dozens of references cited in the four links > contained in my original message, *links that you sniped now*, he can > find the experimental stuff, the rigorous theorems, and the extra > info :-D > > --http://www.canonicalscience.org/ > > BLOG:http://www.canonicalscience.org/publications/canonicalsciencetoday/ca...- Hide quoted text - > > - Show quoted text - Geometry moves with the flow of mass through space. This is a nonlocal effect of the geometry field moving below light speed as mass moves. Mitch Raemsch |