Re: The speed of gravity revisited

On Apr 18, 4:09 pm, carlip-nos...@xxxxxxxxxxxxxxxxxxx wrote:
Tom Van Flandern <to...@xxxxxxxxxxxxxxxx> wrote:

Playing with the definitions of words does no one trying to follow this
discussion any good. You avoid defining "gravitational influences" and just
cite a reference. However, no one is disputing that changes in gravitational
potential (the subject of the field equations) propagate at the speed of
light, c. I am always careful to state that "the speed of gravity" measured
by the six available experiments always means the 3-space propagation speed
of gravitational force, and has nothing to do with changes in gravitational
potential.

That's garbage, Tom.

I used the term "gravitational influence" simply to avoid getting into a
pointless debate about whether gravity in GR is "really" or force or not.
If you would go and read Low's paper, you would see that he is clearly
contradicting your claim.

Low’s paper is full of handwaving. Your proposal to nullify the speed
of gravity through aberration is even more faulty. As a scientist,
how can you live with that? Where is your ethics?

What Low shows is the following:

Let R be an arbitrary region in space (at a fixed time, say t=0) containing
some sources of gravitation. Let p be a point outside R, at a distance d
from R -- that is, for which the closest point in R is a distance d away.

At time t=0, change conditions in R any way you want -- move the masses
around, add more masses, take some away, anything at all, as long as you
don't change anything outside R. What happens at p? Low shows that it
is a clear, unequivocal, unambiguous prediction of GR that nothing
whatsoever changes at p until a time d/c has passed.

To repeat: change the source of gravity in R any way you want. According
to GR, nothing at all happens at a point p outside R until the time for a
light signal to reach p from R has passed. By any sensible definition of
"speed" I can imagine, that means that gravity propagates at the speed
of light.

What you are saying is equally valid for anything including Newton’s
law of gravity. It is an extension to the theory of non-causality.
<shrug>

If you accept this, then we are merely arguing over semantics (although I
would add that your definition of "speed of gravity" must be truly bizarre).
If you don't accept this, then you don't accept "the mathematics of GR."
Period.

If you accept there is no paradox in causality or in anything, a well
thought-out experiment would have no problem measuring the propagation
speed of gravitational effect. As Dr. Van Flandern has pointed out,
all indicate this speed to be magnitudes higher. If aberration does
not work for you, you must accept the experimental results which would
falsify GR in doing so. If not, you have no right to claim yourself a
physicist. <shrug>

You are guilty of

** MYSTICISM IS WIDSOM
** FAITH IS THEORY


.

Relevant Pages

  • Re: The speed of gravity revisited
    ... It concerns only the propagation speed of changes in the gravitational potential field, about which there is no dispute -- it is speed c. ... In particular, physics is concerned about the direction of the arrow of causality, whereas math is not. ... You need to study the two different physical interpretations of GR, then come to understand why one of them is now off the table, and why the other makes the physics of gravity easier to understand for everyone. ... is, in a static situation it simply is not possible to distinguish among models in which "gravitational force" propagates with different speeds, because for any propagation speed whatsoever one obtains the same "gravitational force" and its direction. ...
    (sci.physics.relativity)
  • Re: Tom Van Flandern and Newtonian Gravity
    ... assuming infinite propagation speed. ... were talking about a substitute for gravity, ... that "spacetime" means proper time, ... spacetime intervals are proper time intervals multiplied by c, ...
    (sci.physics.relativity)
  • Re: Tom Van Flandern and Newtonian Gravity
    ... replacement physics interpretations for the math of GR and QED. ... to the notion that superluminal speeds contradicted causality. ... propagation of gravity in forward time, ...
    (sci.physics.relativity)
  • Re: Doubts about relativity dogmas
    ... not involve propagation in any meaningful sense relevant to gravitation. ... Because GR uses retarded potentials without retarded ... When people say "gravity propagates at the speed of light in GR", ... difference to explain this inconsistency is that the propagation speeds ...
    (sci.physics.relativity)
  • Re: The speed of gravity revisited
    ... Special relativity has now been falsified in favor of Lorentzian relativity. ... ** six experiments showing that the propagation speed of gravitational force is>> c, which contradicts SR, but is in accord with LR having no speed limit. ... If your only concern is that the Lorentz transformations do not work for speeds above c, the references explain why this is not a problem for LR. ... I am always careful to state that "the speed of gravity" measured by the six available experiments always means the 3-space propagation speed of gravitational force, and has nothing to do with changes in gravitational potential. ...
    (sci.physics.relativity)
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