Re: The speed of gravity revisited
- From: "Tom Van Flandern" <tomvf@xxxxxxxxxxxxxxxx>
- Date: Tue, 1 Apr 2008 10:17:33 -0700
Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> writes:
[Roberts]: In the model of GR, gravity does not propagate at all, but changes in gravity propagate with speed c.
That is directly in contradiction to experiment and observations. Binary pulsars are an obvious example, as I demonstrated (without any dissent) in Reference B below. But even the simplest orbit computation program can show the same thing. If you use light-time-retarded positions of bodies to compute orbits, the computed orbits are open spirals, in contradiction to observations.
But you've obviously never done the experiment yourself, or have used only propagation delays in the potential field, which are irrelevant for orbit computation. See Reference (C).
There is no way known to any person on this planet to avoid the conclusion that gravitational force propagates >> c without invoking some kind of physical miracle, such as an effect without a cause or the creation of new momentum out of nothingness. Mathematical relativists don't seem bothered by such miracles. Meanwhile, real world physicists know they must not invoke miracles in their theories because that makes them non-falsifiable, and therefore unscientific. [See Reference E.]
[Roberts]: The GR model agrees with all these "evidences", and indeed it accounts MUCH more accurately than the Newtonian model for measurements in the solar system (including the perihelia of Mercury and other planets, the Shapiro time delay, the bending of EM radiation by the sun, the operation of the GPS, the frame dragging measured by the LAGEOS satellites, etc.).
True but irrelevant because GR is a field theory and describes only the field. The gravitational potential field causes all the effects on your list. But it does not cause ordinary orbital motion. Nor do the field equations describe ordinary orbital motion. To get that, one must take a gradient of the potential (or its equivalent) to get what you like to call an "approximation" theory. In simple, classical physics lingo, that process develops an expression for the 3-space (Euclidean) acceleration of bodies in coordinate time, which gives the orbital motion, which is then compared against astronomical observations made in Euclidean 3-space using proper time clocks.
Try computing an orbit with GR just once in any system with at least two significant masses, and you will discover that you cannot do it without adopting near-infinite gravitational force propagation speed between bodies applying forces to one another. Then the dawn will come, and you will finally understand what the "speed of gravity" issue is about.
[Roberts]: it is MUCH better to discuss models and their agreement with experiments than to discuss MODEL-DEPENDENT quantities like "speed of gravity".
The "speed of gravity" is not a model-dependent concept except at the level of parts per 100 million, any more than "perihelion motion" is model-dependent. Its simple meaning is: When a source mass accelerates, the speed of gravity is the ratio of the distance of a target body to the time elapsed before the target body responds. And every known experiment measures that elapsed interval to be zero within experimental error, making the speed of gravity >> c and approximately infinite.
Relativists like to redefine the concept to refer to the speed of changes in the gravitational potential field, which everyone agrees is c. But that refers to gravitational waves, and avoids the issue of the propagation speed of gravitational force for determining the ordinary orbital motion of two masses around a common center of mass. One must either give up the causal link to a source mass, or agree that the force propagates from the source mass to the target body faster than c.
Tom Van Flandern does not understand the real issues, and uses egregious PUNs to promulgate his claims. In particular, what he calls "speed" is not what anybody else would call "speed". The experiments he cites do NOT measure speed (usual meaning), and their actual measurements are fully consistent with GR, in which nothing propagates faster than c.
Quit making up nonsense. The published papers are in references (A), (B), (C), and (D) below. "Speed" has its unambiguous, classical meaning in all of them, as the editors, reviewers, and readers have all understood.
Where are your publications on the subject?
[Juan]: For calculations of orbits we have to use the actual positions of bodies and not the perceived locations.
[Roberts]: True in Newtonian mechanics; irrelevant in GR.
The comparison of theory with observations is not relevant? How absurd! You are disconnected from reality.
References:
** (A) "Possible new properties of gravity", Astrophys.&SpaceSci. 244:249-261 (1996); http://metaresearch.org/cosmology/gravity/possiblenewpropertiesofgravity.asp
** (B) "The speed of gravity - What the experiments say", Phys.Lett.A 250:1-11 (1998); http://metaresearch.org/cosmology/speed_of_gravity.asp
** (C) "Reply to comments on 'The speed of gravity'", Phys.Lett.A 262:261-263 (1999).
** (D) "Experimental Repeal of the Speed Limit for Gravitational, Electrodynamic, and Quantum Field Interactions", T. Van Flandern and J.P. Vigier, Found.Phys. 32:1031-1068 (2002); preprint under title "The speed of gravity - Repeal of the speed limit" at http://metaresearch.org/cosmology/gravity/speed_limit.asp
** (E) "Physics has its principles", in Gravitation, Electromagnetism and Cosmology, K. Rudnicki, ed., C. Roy Keys Inc., Montreal, 87-101 (2001);
http://metaresearch.org/cosmology/PhysicsHasItsPrinciples.asp
Tom Van Flandern - Sequim, WA - see our web site on frontier astronomy research at http://metaresearch.org
.
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