Re: The speed of gravity revisited

Tom Roberts writes:

[TomVF]: Publication of experiments funded in-house is often published in-house at most major science agencies because that enhances the agency's reputation. These are still peer-reviewed papers. In-house editorial boards are usually stricter than journal referees because they feel the reputation of their home institution is at stake.

[Roberts]: Nonsense. That may be the policy of YOUR "Meta-Research organization", but it most definitely is not the policy of any major university -- "publish or perish" applies....

You continue to make absurd claims without any basis. Each government agency I worked for or worked with had its own editorial board for precisely the purpose I specified. Probably dozens of people reading this can confirm that is the case for their own agencies.

[Roberts]: Though it is QUITE CLEAR that the in-house "peer review" of metaresearch.org is ludicrous and/or involves "peers" who do not understand relativity.

Certainly, none of our reviewers has so limited a knowledge of the subject as you do.

[TomVF]: A better question is, given the importance of this result and the lack of any other experiment to justify what is in the textbooks, why has no one else ever attempted to replicate it, even just to refute Sherwin and Rawcliffe?

[Roberts]: Probably for the simple reason that essentially nobody knows about it.

You missed the thrust of my point. Why has no one anywhere in physics attempted to do an experiment to learn if the force between *accelerating* charges propagates at speed c or faster? It's a pretty important matter, and many physics texts read as if the experiment was done and the result is known. That kind of mythology retards progress in the field.

[TomVF]: The derivation of equations of motion from those [solutions of the field] equations is not unique until one specifies the speed of interactions. That speed has always been taken as instantaneous by GR, which is the correct assumption.

[Carlip]: Nonsense.

[TomVF]: That's your argument? Nonsense? You don't even say what point you consider nonsense: that the equations of motion depend on an assumption about the interaction speed, or that GR makes the correct assumption.

[Roberts]: Both (sort of) -- in GR the equations of motion for a test particle have no dependence whatsoever on any "interaction speed".

Right because, as I explained, that "interaction speed" term was driven to zero by adopting infinite gravitational force propagation speed.

[Roberts]: All one needs to do is LOOK AT THE MATH to see this is so.

And all one needs to do is understand basic physics to see why one thing cannot act on another without a material, tangible entity passing between them. Any such entity obviously has a propagation speed.

[TomVF]: You will have to do better.

[Roberts]: No, the problem is yours, and YOU will have to understand the mathematics of GR. It is quite different from what you try to discuss.

No one can apply math to physics until they understand physics. You wish to ignore all issues of physics, so your position remains indefensible.

Can you even imagine an issue we might have with the math? This discussion is all about what the math means to physics. But I understand why you keep harping back to mythical math issues because you are out of your comfort zone when discussing the physics behind the math.

[Carlip]: The geodesic equations are ...

[TomVF]: The solution is unique for any fixed point in the field.

[Roberts]: No. You keep showing that you simply do not understand the math. The entire solution is unique, giving the trajectory of the test body. This holds for every point the test body ever occupies, not just some "fixed point".

If that were true, then the math would have nothing to do with reality. In the physical world, source masses change target body momentum via the propagation of material, tangible entities ("force" carriers). Such forces are necessarily retarded if the target body is moving. Aberration is simply the ratio of transverse target body speed to force propagation speed.

The only physical justification for ignoring the retardation of forces (setting aberration to zero) in the math is the adoption (whether implicit or explicit) of infinite force propagation speed. If you don't understand this basic physics point, then you have no defense for drawing conclusions about physics from the math.

[Roberts]: NONE of the experiments you cite are sensitive enough to resolve the difference between the predictions of Newton and GR.

The experiments are looking for a retardation effect four orders of magnitude larger than GR effects such as light-bending or perihelion advance. You apparently don't know much celestial mechanics, and should refrain from comments in that subject area lest you remove all doubt.

[Roberts]: how little you read what other people write.

All you write is blustering claims and insults like this one. When have you ever attempted to communicate something of substance by mentioning an experiment, observation, reasoned argument, or citation? Your entire stance seems to rest on an appeal to authority, a type of argument never valid in science. When any issue is disputed in science, only the merits of the arguments matter, not the number or prestige of experts on one side of the issue.

[Roberts]: there is an APPROXIMATION to GR that has a propagation delay of c, and in which the orbit does not "spiral" significantly

Wrong. If you can produce such an approximation (by experiment, observation, reasoning, or citation), I'll be happy to concede victory to you. I can only hope that you are gracious enough to reciprocate when you find out that no such approximation exists.

For example, the gravitational radiation delay is proportional to c^-5, and is utterly insignificant compared to the matters we have been discussing. The light-bending, gravitational redshift, propagation speed delay, and perihelion advance factors are all proportional to c^-2, which is orders of magnitude smaller than light-speed aberration everywhere in the solar system. And any computer experiment, whether using Newtonian or GR equations of motion, immediately demonstrates that propagation delays of c generate rapid spiral orbits.

Do you accept this challenge to show a propagation delay of c in the GR equations of motion, with little spiraling? Your efforts should be instructive to both of us and to our readers.

[Roberts]: Steve Carlip has discussed a case for which an exact computation in GR shows the direction of the 3-acceleration of a test body does not point to the instantaneous position of the source.

Steve's case is theoretical and cannot be demonstrated experimentally. The one I cited is an actual experimental result. Binary pulsars attract one another from their instantaneous positions rather than from their extrapolated, light-time-retarded positions.

BTW, I do have issues with the math of GR for strong fields and high speeds. But nearly everybody cautions that GR has not been adequately tested in that domain, and lots of relativists have suggested that changes may be needed.

[Roberts]: One of [TomVF's web site] papers (http://metaresearch.org/cosmology/gravity/gravity.asp) attempts to use the GPS satellites to "prove" that the term -xv/c^2 does not appear in the Lorentz transform for t=>t', thus showing he does not understand the basics of SR, what an inertial frame is, or how they apply (in a very limited way) to the GPS.

That paper has had thousands of readers, but none so confused as to make such an absurd interpretation you propose. The vx/c^2 term is not needed in LR because the transformations work only one way, from the local gravitational potential frame to the moving frame. But that term is an intrinsic, integral part of SR. The important (experimentally verified) part of the time transformation, the gamma term, is common to both SR and LR. As I remarked before, GPS uses the LR form of the equations *without* the vx/c^2 term. GPS synchronizes all clocks in all reference frames to the USNO master clock. Then all those clocks remain synchronized (except for a small, periodic eccentricity effect that vanished for circular orbits), despite relativity corrections being quite large (~40,000 nanoseconds per day).

I give you credit for trying to read the paper. Please try again, now that we are past the first point where your understanding of it failed. -|Tom|-


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

.

Relevant Pages

  • Re: Career advice needed.
    ... who post here semiregularly are full professors at math or physics ... provide help to a deserving aspiring student. ... I do know of several cases of a Math graduate program accepting ... study these prereqs on your own from books (by paying a yearly fee you ...
    (sci.physics.research)
  • Re: The physical motions of photons in free space!
    ... >the choice that "The rest frame of the ether is what ... The base to SR is a math base, ... Any physics equation, ...
    (sci.physics.relativity)
  • Re: Physics versus Mathematics
    ...  Bend your math anyway you like. ... Go to the beach and see if a wave imparts some force. ... can't quite do the same for gravity. ... physic or what we describe as physics, ...
    (sci.physics.relativity)
  • Re: Why relativists dont understand Einsteins 1905 mathematics.
    ... speeds we are used to. ... It cannot mutate into waves for part of the journey because by their very nature waves spread out and their energy density reduces. ... The waves of Maxwell's wave in aether theory do not physically exist. ... Essentially what Einstein assumed was that EM theory is correct and that therefore the laws of mechanics had to change resulting in having to ditch 3 long standing and apparently sensible axioms of physics. ...
    (sci.physics.relativity)
  • The Proper understanding of Modern Physics.
    ... The Proper understanding of Modern Physics. ... There is no desire to destroy the math of SR. ... The MMX disproved the ether. ... measurement, but we also had to then determine what ...
    (sci.physics.relativity)