Re: The speed of gravity revisited

"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> writes:

[Roberts]: For those unwilling to wade through the umpteenth time this has been discussed, here is the bottom line: ... None of the experiments Van Flandern cites refute GR ...

I am sorry you can't keep your correspondents straight. For the umpteenth time, I agree with GR as a mathematical theory. Nothing I've said here is in any way a refutation of GR.

But equations can have many different physical interpretations. Even the biggest names in the field (Einstein, Dirac, Feynman) agree GR has at least two different physical interpretations. The experiments and physical principles have now eliminated one of those - the geometric interpretation. But that still leaves us with the field interpretation of GR, the one those great physicists preferred anyway.

So unless you are unable to unlearn something you were once taught, you just need to switch the physical interpretation you support, leaving the math of GR as it is, and you will again be in accord with experiments and physical principles. Do you have some problem with going back to the way Einstein taught GR (field interpretation), instead of the unphysical geometric interpretation that became popular from the 1970s forward?

[Roberts]: In the model of GR, gravity does not propagate at all, but changes in gravity propagate with speed c.

[TomVF]: That is directly in contradiction to experiment and observations.

[Roberts]: No, it is not. But to understand this one must actually use GR, which you quite clearly do not understand (more on this below).

You are making a fool of yourself. I cited a detailed set of experiments from the published, peer-reviewed literature; while you make unbacked claims without an ounce of attempted justification. You seem to know only the geometric interpretation of GR, which lacks causality for new motion and momentum conservation between source mass and target body.

When you repeat geometric GR statements such as "gravity does not propagate at all", that requires redefining the word "gravity" to mean just the refraction effects the field has on electromagnetic signals and eliminating the main *force* that governs the orbital motions of planets, moons, satellites, and spacecraft. In normal physics, "force" means the time rate of change of (3-space) momentum by definition. (Consult any dictionary or encyclopedia that gives definitions by field of application). So orbital motion represents a force by definition of the word. And linear momentum involves a propagation velocity by definition. So there is no physics issue in that claim, just an issue of the definition of words. With your re-definitions, there is no longer an active connection between a source of gravity and the effect it is currently having on target bodies, which makes no sense in real physics.

In our many exchanges, you have shown extensive unfamiliarity with celestial mechanics, the field that tests GR against astronomical observations. But that doesn't seem to cause you to hesitate to make claims about what the experiments and observations show. For example:

All the experiments I cited demonstrate that gravity propagates faster than c. The Taylor-Hulse binary pulsar demonstrates that *changes* in gravity also propagate much faster than c. This flatly contradicts your claim. Therefore, the burden is now on you to point out the exact error in my proof in the cited published paper, or to concede the point. Just pontificating is not a valid, scientific response.

[TomVF]: Binary pulsars are an obvious example, as I demonstrated (without any dissent) in Reference B

[Roberts]: To claim you demonstrated it is wrong, and to claim "without dissent" is a bald-faced lie. You even published a comment on the major dissenting paper.

Now you are just being a twerp. (If you have any doubt about whether that is a counter-insult, look up the definition. I use them so rarely that I wouldn't want you to miss one.) Reference B contains a proof, using binary pulsars, that changes in gravity propagate much faster than c. You obviously did not even look at it or you wouldn't be saying there is something wrong with it, then quickly attempting to change the subject by calling me a liar so no one will notice that you neglected to give any clue about what is wrong with this published and now-widely-accepted proof, or even that you understand the proof. Your "hit and run" tactic did not work.

Regarding the "lie" part, I must presume you are referring to Kopeikin's failed Jupiter-quasar appulse experiment. Several of the leading names in relativity today commented that his experiment had no bearing on the speed of gravity, but merely measured the speed of electromagnetic signals (c) as that speed enters any light-bending experiment. You don't need to rely on my refutation of Kopeikin because your senior colleagues have done that job for me. But Kopeikin wasn't talking about gravitational force or "changes in gravity". So even if he had been right, his result would not support your claim.

In fact, you won't find a single knowledgeable relativist on USENET who can support your claim that "changes in gravity propagate at speed c". When binary pulsars accelerate, that is a change in the gravity they exert on one another, and those changes act on the other body much faster than the light-time between them. You might still find someone who will mistake this claim to mean that changes in gravity are gravitational waves. But that too is physical nonsense. When I walk around a room and trigger a response in a sensitive gravimeter, I am indeed changing the gravitational force I exert on the gravimeter, but I am not generating gravitational waves at any detectable level. And no one who knows what he/she is talking about would claim otherwise. Gravitational waves have never yet been detected within our solar system.

[TomVF]: 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.

[Roberts]: How silly can you get???? The subject here is GR and its relation to experiments. To address that you must use GR, and not whatever it is you have cobbled together with "light-time-retarded positions".

How exactly do you propose to learn anything about the "relation of GR to experiments" without computing orbits from GR equations of motion (i.e., celestial mechanics, my professional specialty)? I have to agree that this is getting very silly indeed. But then, for some reason you feel compelled to pretend you know something about fields in which you know nothing.

I have previously given you the references to the three main papers converting the Schwarzschild solution into 3-space equations of motion: Einstein-Infeld-Hoffman, Robertson-Noonan, and Damour-Deruelle. Have you read these papers yet? Do you have any idea what their meaning is? Yet this step is crucial to understanding the comparison of GR with observations, and indeed to understanding the whole "speed of gravity" issue.

[Roberts]: I repeat: In the model of GR, gravity does not propagate at all, but changes in gravity propagate with speed c. You have said NOTHING that addresses this, much less refutes it as you claim.

I gave you specific references to prove the points I made. You provide nothing but exaggerated claims and insults. Are you unable to read published papers with understanding, or is it beneath you? My Reference B proves what I said it proves. The other references support my other statements. Read and learn. Only then can you be qualified to criticize.

[TomVF]: 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.

[Roberts]: That a GROSS overstatement. What you clearly mean is "Tom Van Flandern does not know how to do this". And it's also clear that your lack of knowledge is at fault, as the current primary theory of gravitation does PRECISELY this.

The pattern continues. I mention observations, experiments, reasoning, and citations, such as the Foundations of Physics article Vigier and I published. You say I'm wrong and ignorant and offer *nothing* of any substance, just unsupported claims and accusations. So which of us is displaying his ignorance?

[TomVF]: GR is a field theory and describes only the field.

[Roberts]: Then how is it that GR is applied to all those experiments and
measurements? Clearly GR describes more than the "field" -- it describes
THOSE EXPERIMENTS AND MEASUREMENTS.

The field equations describe only the field and the field effects: light-bending, gravitational redshift, etc. The field itself is unobservable. So to make comparisons with astronomical observations made in a Euclidean coordinate system, solutions to the field equations must be converted to 3-space equations of motion, then numerically integrated, then used to make predictions, which may then be compared to observations.

The field equations and their solutions use the speed of light. But in the step where they are converted to 3-space equations of motion (which are expressions for *gravitational force*), instant force propagation must be assumed because delayed forces, even delays just for changes in forces, lead to total failure of the theory to agree with observations.

Why do you choose to resist learning, and to hurl insults, instead of educating yourself? Are you afraid there might be something to what I have published about several times now? Or are you just afraid of what your colleagues might do if you found something I wrote that you agreed with?

[Roberts]: Speed is measured by using two synchronized clocks to measure the travel time along a path measured with standard rulers at rest in the same frame the clocks are synchronized in. Which of the experiments you reference have done that? -- NONE.

Two of the experiments use actual speed as you just defined. Three others use aberration, which is the ratio of transverse orbital speed to force propagation speed. So, all these experiments allow us to determine the actual propagation speed of gravitational forces in a model-independent way using the classical meaning of "speed". You just needed to know the meaning of "aberration" to realize that.

You spend countless hours dealing with some uneducated and unknowledgeable people on USENET. I've seen you research topics and give reasoned responses, as for example when dealing with the few remaining folks still touting Miller's 1930s data allegedly showing anisotropies of light speed of ~ 8 km/s when GPS has set upper limits to such anisotropies more than 1000 times smaller.

Yet how many of the people you deal with are professionals who publish regularly in the major, peer-reviewed journals and deal with every objection to the satisfaction of neutral parties? What exactly do you want to see to move you to take this material seriously? Or are you one of those physicists about whom it is said that "physics advances one funeral at a time"?

Your utterances reflect badly on your reputation because of your unwillingness to read published works and either learn new things, or at least discuss the substantive issues they raise instead of using denial, loud claims, and insults. -|Tom|-


Tom Van Flandern - Sequim, WA - see our web site on frontier astronomy research at http://metaresearch.org

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