Speed of gravity
in [Relativity]
|
From: G. L. Bradford on 2 Mar 2010 12:24 "G. L. Bradford" <glbrad01(a)insightbb.com> wrote in message news:DuednYPtQ7RcSRHWnZ2dnUVZ_ridnZ2d(a)insightbb.com... > > "BURT" <macromitch(a)yahoo.com> wrote in message > news:7f7539e6-ae95-4eff-bc8e-101469ac2464(a)u19g2000prh.googlegroups.com... > On Mar 1, 10:22 pm, "G. L. Bradford" <glbra...(a)insightbb.com> wrote: >> <carlip-nos...(a)physics.ucdavis.edu> wrote in message >> >> news:hmguvj$1f6o$1(a)news.telesweet.net... >> >> >> >> >> >> > 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. >> >> > It's also true that if you start with *Newtonian* gravity and stick >> > in a finite propagation speed, orbits become dramatically unstable. >> > This does *not* happen in general relativity, though; in GR, there >> > are additional velocity-dependent interactions that almost (but not >> > quite) cancel the instability. 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. >> >> > 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. >> >> > 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. But if you look at the force exerted by a charge >> > moving at a constant velocity, it points towards the "instantaneous" >> > position of the charge, not the retarded (light-travel-delayed) >> > position. This is discussed in the Feynman Lectures, Vol. II, chap.21 >> > -- you can see very explicitly that the effects of finite propagation >> > speed are canceled to lowest order by additional velocity-dependent >> > interactions that effectively "extrapolate" the position of the moving >> > charge. >> >> > Steve Carlip >> >> ========================= >> >> Two bodies are in an orbital system, one orbiting the other as they >> travel >> through the universe. The speed of light gives one body the relative >> position of the other to be 8 light minutes. Their fields of gravity fix >> the >> position of each relative to other at [8 light minutes plus 8 minutes]. >> The >> Earth does not orbit the history 8 light minutes away, it orbits the >> solar >> mass 8 light minutes plus 8 minutes away. It is gravitationally aware of >> the >> exact actual position of the sun relative to itself, as is the sun >> gravitationally aware of the exact actual position of the Earth relative >> to >> itself. The speed of light versus gravity's [field] being nothing less >> than >> gravity's [singularity] by another name. >> >> You told Art that the bodies orbit the history, not the mass. The >> seemingly small difference in the example above might not mean much, if >> anything, to the lazy but means everything to physics. You separated the >> sun's field, the sun's well, from the sun's mass 8 minutes worth at the >> Earth's distance from it. You would separate the field, the well, from >> the >> mass even more at Mars' distance from it....and even more at Jupiter's >> distance from it...and even more at Saturn's distance....and so on. >> >> GLB >> >> =========================- Hide quoted text - >> >> - Show quoted text - > > The gravity field moves slower than lght as it's mass moves. The field > moves nonlocally. > > Mitch Raemsch > > ========================= > > A gravity field is singular in space and time, in space-time, not plural! > At one light second's distance from the body it exists at one light second > plus one second in the universe. At ten light seconds distance from the > body it exists at ten light seconds plus ten seconds in the universe. At > one thousand light seconds from the body it exists at one thousand light > seconds plus one thousand seconds in the universe. All of the [plus] > unobservable and singularly advanced in space and time, in space-time, > over the speed of light. > > Gravity's field (gravity's singularity), integrally, has nothing to do > with speed at all, no matter if it's 'c' or even infinity. It's singular, > damn it! The gravity field is singular, always existing and in motion as > singular, a singularity in space and time, in space-time. It does not > exist one light second from the body, which is to say it does not exist -1 > second to the body's 0. It exists that -1 second + 1 second to equal 0 (0 > = 0). At one light second's distance (-) from any gravitational body (0), > it has already (+) beaten the speed of light by one second (0 = 0). At ten > light seconds distance (-), it has already (+) beaten 'c' by ten seconds > (0 continues to equal 0). And the inequality between the speed of light > and gravity's field (gravity's singularity) only continues to grow with > all accumulating distance the speed of light has to contend with (that > gravity's singular field does not have to contend with). > > Any so-called gravitational wave (made out to be the material entity of > the gravity field) doing the speed of light would be tied to > an -observable- massless history [behind] rather than the -unobservable- > massive body [ahead]. Any body at any distance trying to orbit a massless > history rather than a massive body is certainly going to have an > "unstable" orbit. > > GLB > > ========================= If the speed of light were to measure itself locally against any point of gravity's field (against gravity's singularity) it would always find itself to be doing 'c' at that point. Which is to say, again, any point at all in any extent at all of gravity's field! To include any plane! GLB =========================
From: BURT on 2 Mar 2010 15:28 On Mar 2, 1:04 am, "G. L. Bradford" <glbra...(a)insightbb.com> wrote: > "BURT" <macromi...(a)yahoo.com> wrote in message > > news:7f7539e6-ae95-4eff-bc8e-101469ac2464(a)u19g2000prh.googlegroups.com... > On Mar 1, 10:22 pm, "G. L. Bradford" <glbra...(a)insightbb.com> wrote: > > > > > > > <carlip-nos...(a)physics.ucdavis.edu> wrote in message > > >news:hmguvj$1f6o$1(a)news.telesweet.net... > > > > 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. > > > > It's also true that if you start with *Newtonian* gravity and stick > > > in a finite propagation speed, orbits become dramatically unstable. > > > This does *not* happen in general relativity, though; in GR, there > > > are additional velocity-dependent interactions that almost (but not > > > quite) cancel the instability. 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. > > > > 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. > > > > 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. But if you look at the force exerted by a charge > > > moving at a constant velocity, it points towards the "instantaneous" > > > position of the charge, not the retarded (light-travel-delayed) > > > position. This is discussed in the Feynman Lectures, Vol. II, chap.21 > > > -- you can see very explicitly that the effects of finite propagation > > > speed are canceled to lowest order by additional velocity-dependent > > > interactions that effectively "extrapolate" the position of the moving > > > charge. > > > > Steve Carlip > > > ========================= > > > Two bodies are in an orbital system, one orbiting the other as they travel > > through the universe. The speed of light gives one body the relative > > position of the other to be 8 light minutes. Their fields of gravity fix > > the > > position of each relative to other at [8 light minutes plus 8 minutes]. > > The > > Earth does not orbit the history 8 light minutes away, it orbits the solar > > mass 8 light minutes plus 8 minutes away. It is gravitationally aware of > > the > > exact actual position of the sun relative to itself, as is the sun > > gravitationally aware of the exact actual position of the Earth relative > > to > > itself. The speed of light versus gravity's [field] being nothing less > > than > > gravity's [singularity] by another name. > > > You told Art that the bodies orbit the history, not the mass. The > > seemingly small difference in the example above might not mean much, if > > anything, to the lazy but means everything to physics. You separated the > > sun's field, the sun's well, from the sun's mass 8 minutes worth at the > > Earth's distance from it. You would separate the field, the well, from the > > mass even more at Mars' distance from it....and even more at Jupiter's > > distance from it...and even more at Saturn's distance....and so on. > > > GLB > > > =========================- Hide quoted text - > > > - Show quoted text - > > The gravity field moves slower than lght as it's mass moves. The field > moves nonlocally. > > Mitch Raemsch > > ========================= > > A gravity field is singular in space and time, in space-time, not plural! There is more than one curved geometry when there is more than one gravitational source. Mitch Raemsch
From: Koobee Wublee on 2 Mar 2010 17:06 On Mar 1, 9:53 am, carlip-nos...(a)physics.ucdavis.edu wrote: > 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. You can say the same thing for Newtonian gravity. <shrug> > I wouldn't say Einstein "assumed" this -- it was not put > into the derivation of the field equations of general relativity, Yes, it is not possible to show gravitational effect propagates at a certain speed just by examining the field equations. <shrug> > but is, rather, a conclusion. Conclusion? You mean by a unanimous vote just like our congressmen unanimously vote for their salary increase every single year while the general public experience great hardship in this dire economy. <shrug> > 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. It is indeed a good one for an early April Fool joke. How do you like the warp drive thing? > It's also true that if you start with *Newtonian* gravity and stick > in a finite propagation speed, orbits become dramatically unstable. Yes, Laplace showed the speed of gravity must be several billion times the order of the speed of light to demonstrate a stable solar system. <shrug> > This does *not* happen in general relativity, though; in GR, there > are additional velocity-dependent interactions that almost (but not > quite) cancel the instability. This fix does not appear in the field equations. So, it is a band- aide added later on to solve this problem. <shrug> > 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. I thought the late Van Flandern did show that aberration of earth results in a catastrophic model of the solar system. <shrug> > 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. The case for binary stars utilizes MATHEMAGICS to conjure up gravitational waves from the cracks of spacetime where in the case of the ever so innocent Schwarzschild metric, it does radiate energy. This is totally contradictory to the geodesic equations that show a complete conservation of energy under the Schwarzschild metric. <shrug> > 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. But if you look at the force exerted by a charge > moving at a constant velocity, it points towards the "instantaneous" > position of the charge, not the retarded (light-travel-delayed) > position. This is discussed in the Feynman Lectures, Vol. II, chap.21 > -- you can see very explicitly that the effects of finite propagation > speed are canceled to lowest order by additional velocity-dependent > interactions that effectively "extrapolate" the position of the moving > charge. The so-called vigorous MATHEMAGICS only CONCLUDES what you want to believe. If you go back to the model of an absolute frame of reference, any simple mathematical diagram will show so where relativity fails big time. <shrug>
From: BURT on 2 Mar 2010 20:17 On Mar 2, 2:06 pm, Koobee Wublee <koobee.wub...(a)gmail.com> wrote: > On Mar 1, 9:53 am, carlip-nos...(a)physics.ucdavis.edu wrote: > > > 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. > > You can say the same thing for Newtonian gravity. <shrug> > > > I wouldn't say Einstein "assumed" this -- it was not put > > into the derivation of the field equations of general relativity, > > Yes, it is not possible to show gravitational effect propagates at a > certain speed just by examining the field equations. <shrug> > > > but is, rather, a conclusion. > > Conclusion? You mean by a unanimous vote just like our congressmen > unanimously vote for their salary increase every single year while the > general public experience great hardship in this dire economy. > <shrug> > > > 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. > > It is indeed a good one for an early April Fool joke. How do you like > the warp drive thing? > > > It's also true that if you start with *Newtonian* gravity and stick > > in a finite propagation speed, orbits become dramatically unstable. > > Yes, Laplace showed the speed of gravity must be several billion times > the order of the speed of light to demonstrate a stable solar system. > <shrug> > > > This does *not* happen in general relativity, though; in GR, there > > are additional velocity-dependent interactions that almost (but not > > quite) cancel the instability. > > This fix does not appear in the field equations. So, it is a band- > aide added later on to solve this problem. <shrug> > > > 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. > > I thought the late Van Flandern did show that aberration of earth > results in a catastrophic model of the solar system. <shrug> > > > 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. > > The case for binary stars utilizes MATHEMAGICS to conjure up > gravitational waves from the cracks of spacetime where in the case of > the ever so innocent Schwarzschild metric, it does radiate energy. > This is totally contradictory to the geodesic equations that show a > complete conservation of energy under the Schwarzschild metric. > <shrug> > > > 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. But if you look at the force exerted by a charge > > moving at a constant velocity, it points towards the "instantaneous" > > position of the charge, not the retarded (light-travel-delayed) > > position. This is discussed in the Feynman Lectures, Vol. II, chap.21 > > -- you can see very explicitly that the effects of finite propagation > > speed are canceled to lowest order by additional velocity-dependent > > interactions that effectively "extrapolate" the position of the moving > > charge. > > The so-called vigorous MATHEMAGICS only CONCLUDES what you want to > believe. If you go back to the model of an absolute frame of > reference, any simple mathematical diagram will show so where > relativity fails big time. <shrug> There is no Doppler gravity. The field moves all at once with its mass motion. Mitch Raemsch
From: BURT on 2 Mar 2010 20:20
On Mar 2, 5:17 pm, BURT <macromi...(a)yahoo.com> wrote: > On Mar 2, 2:06 pm, Koobee Wublee <koobee.wub...(a)gmail.com> wrote: > > > > > > > On Mar 1, 9:53 am, carlip-nos...(a)physics.ucdavis.edu wrote: > > > > 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. > > > You can say the same thing for Newtonian gravity. <shrug> > > > > I wouldn't say Einstein "assumed" this -- it was not put > > > into the derivation of the field equations of general relativity, > > > Yes, it is not possible to show gravitational effect propagates at a > > certain speed just by examining the field equations. <shrug> > > > > but is, rather, a conclusion. > > > Conclusion? You mean by a unanimous vote just like our congressmen > > unanimously vote for their salary increase every single year while the > > general public experience great hardship in this dire economy. > > <shrug> > > > > 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. > > > It is indeed a good one for an early April Fool joke. How do you like > > the warp drive thing? > > > > It's also true that if you start with *Newtonian* gravity and stick > > > in a finite propagation speed, orbits become dramatically unstable. > > > Yes, Laplace showed the speed of gravity must be several billion times > > the order of the speed of light to demonstrate a stable solar system. > > <shrug> > > > > This does *not* happen in general relativity, though; in GR, there > > > are additional velocity-dependent interactions that almost (but not > > > quite) cancel the instability. > > > This fix does not appear in the field equations. So, it is a band- > > aide added later on to solve this problem. <shrug> > > > > 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. > > > I thought the late Van Flandern did show that aberration of earth > > results in a catastrophic model of the solar system. <shrug> > > > > 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. > > > The case for binary stars utilizes MATHEMAGICS to conjure up > > gravitational waves from the cracks of spacetime where in the case of > > the ever so innocent Schwarzschild metric, it does radiate energy. > > This is totally contradictory to the geodesic equations that show a > > complete conservation of energy under the Schwarzschild metric. > > <shrug> > > > > 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. But if you look at the force exerted by a charge > > > moving at a constant velocity, it points towards the "instantaneous" > > > position of the charge, not the retarded (light-travel-delayed) > > > position. This is discussed in the Feynman Lectures, Vol. II, chap..21 > > > -- you can see very explicitly that the effects of finite propagation > > > speed are canceled to lowest order by additional velocity-dependent > > > interactions that effectively "extrapolate" the position of the moving > > > charge. > > > The so-called vigorous MATHEMAGICS only CONCLUDES what you want to > > believe. If you go back to the model of an absolute frame of > > reference, any simple mathematical diagram will show so where > > relativity fails big time. <shrug> > > There is no Doppler gravity. The field moves all at once with its mass > motion. > > Mitch Raemsch- Hide quoted text - > > - Show quoted text - There is also a range for this gravitational domain in the distance. Mitch Raemsch |