On Apr 1, 10:17 am, "Tom Van Flandern" wrote:
Tom Roberts" 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.]

While Professor Roberts is struggling to understand how a binary
system still have to account for gravitational field varying with
time, Professor Carlip addressed your claim that the speed of gravity
being several billion times the speed of light in the following
article. I have seen no public refutation to his work.

http://arxiv.org/abs/gr-qc/9909087

The aberration can also be simply explained by the good old Galilean
transformation. Any apparent distance must be corrected by the
Galilean transform. In this paper, Professor Carlip is suggesting the
gravitational distance between the stars must be corrected by this
aberration. In doing so, it will cause a first-order cancellation on
the issue of the speed of gravity. The argument between you and him
centers around if the aberration must be corrected. Do you have any
fundamental argument to suggest that the aberration should not be
corrected in this case?