Juan R. González-�lvarez wrote:
Tom Roberts wrote on Mon, 14 Apr 2008 14:30:05 +0000:
Don't evade the challenge, use whatever expression
you wish. Use whatever definition of "gravitational force" you wish. But
be sure to meet the challenge: describe how to MEASURE the
"gravitational FORCE" on an orbiting satellite, not any indirect or
model-dependent implications of it (such as orbit parameters, which are
geometrical, not any sort of force).

Excuses excuses excuses...

Yes, that's all you give. Please stop with the excuses and answer the
challenge.


I am still waiting from you to write the force, just that you say cannot
be measured Tom.

OK, here in the context of GR is an expression for the "gravitational
force", in any situation whatsoever (note the expression is enclosed in
square brackets):

[]

That's right, there is no "gravitational force" in GR. That's why I
always place that phrase in quotation marks.


But as I said above, YOU may use any theoretical context you think
appropriate, and use any definition of "gravitational force" you think
appropriate. Just tell us how one can MEASURE it on an orbiting satellite.


Or maybe as usual you are writting about stuff you never studied Tom.

No. I have studied SR and GR, as any perusal of my postings in this
newsgroup would show.


That paper shows how the equation for the orbit (in terms of
gravitational force, which is computed) in the alternative theory is
*independent* of the system of coordinates (whereas you are at least
correct here) the corresponding equation for GR is coordinate dependant.

That sounds like a fine theoretical context for you to use. Why can't you?


Game over.

YOU haven't even started to "play". But this is not a "game", it is a
serious question for you -- why do you think that "gravitational force"
can be measured, and if so, how?

I repeat: if you truly understood this, and there actually was a way to
respond to my challenge, you would have spent MUCH less time typing it
in than you have already spent in all your evasions.


This is the reason which one can speak about *gravitational
force* on that alternative approach.

So "speak" of it, already! In particular, tell us how to MEASURE it.


Tom Roberts

Tom Roberts wrote on Mon, 14 Apr 2008 14:47:56 +0000:

AT MOST what they have established is that the conventional notation is
inadequate to express the subtleties of differentiating a retarded-time
function of the source trajectory with respect to the implicitly-defined
retarded time, and relating it to the coordinate time of the point at
which the fields are to be evaluated. But given the comment by J.D.
Jackson (yes, THAT Jackson, author of _Classical_Electrodynamics_), I'm
not convinced they even did that.

Very much as your current posting, Jackson comment is based in false
atribution, misreading, misunderstanding, and unsound mathematics.

http://arxiv.org/abs/physics/0205041v1


Yes by THAT Jackson

http://arxiv.org/abs/physics/0608054


Try again: Look for a place where they evaluate [eq. 2] at time t rather
than the retarded time t0. THAT is what an "instantaneous interaction"
would involve, not their subtleties about differentiating with respect
to implicitly-defined variables (which may well be valid). The fact that
non-retarded derivatives with respect to {x,y,z,t} appear is due to the
way fields are LOCALLY related to potentials, and due to the fact that
Maxwell's equations are purely LOCAL. This is not any sort of
"instantaneous interaction", because the source trajectory is ALWAYS
evaluated at the retarded time.


"Yours is a statement of profound ignorance in all of its parts."
--- Uncle Al to Tom Roberts in sci.physics.research Feb 2008



--
http://canonicalscience.org/en/misce...guidelines.txt

Tom Roberts wrote on Mon, 14 Apr 2008 21:06:09 -0500:

Juan R. González-�lvarez wrote:
Tom Roberts wrote on Mon, 14 Apr 2008 14:30:05 +0000:
Don't evade the challenge, use whatever expression you wish. Use
whatever definition of "gravitational force" you wish. But be sure to
meet the challenge: describe how to MEASURE the "gravitational FORCE"
on an orbiting satellite, not any indirect or model-dependent
implications of it (such as orbit parameters, which are geometrical,
not any sort of force).

Excuses excuses excuses...

Yes, that's all you give. Please stop with the excuses and answer the
challenge.

Summarizing, you did a strong statement about the gravitational force
(experimental physicists, astronomers enginners are measuring) but you
show unable to write the expression for the force.

· Replying stuff you never studied was your first mistake.

Then you offered us an generic 'argument' (you believed) about why
coordinate dependence of orbits invalidate existence of a physical force,
but in your ignorance of those research topics, you faield to see that
your argument does not apply to theories where the computed (and measured)
gravitational force is coordinate independent (thus not an artifact of
the coordinates choosen).

· Taking too seriously the geometrical approach to gravity was your
second mistake.

Game over.

YOU haven't even started to "play". But this is not a "game", it is a
serious question for you -- why do you think that "gravitational force"
can be measured, and if so, how?

The time of gamming on this newsgroup passed away and i am not longer
reading threads here. Of course, I continue reading spr and spf.

Tom, you are doing a good job here replying several common
misunderstandings about both SR and GR from undergraduate students of
physics, and also from people never studied physics.

You usually cite references (e.g. basic textbooks) on geometrical GR and
you always lack to cite references on *non-geometrical* approach to
gravity.

But since the geometrical formulation has certain range of empirical
validity your geometrical-oriented posters are more a symptom of
incompleteness than of serious misunderstanding about basic gravity.

Moreover, students always can learn more advanced and modern non-
geometrical theories at posterior courses, PhDs, or during postdocs and
then check by themselves the validity of your views about geometry:

http://www.amazon.com/Feynman-Lectur...tiers-Physics/
dp/0201627345

{BLOCKQUOTE
Feynman gave a series of lectures on gravitation at a graduate seminar at
Caltech in 1962.

[...]

This is a more fundamental approach than the usual differential geometric
framework and shows what the equivalence principle really means in terms
of fundamental symmetries. Highly recommended for a modern field theory
viewpoint of GR.
}


I may confess i admire your patience when sometimes you receive some
unfair replies -instead a simple thanks- after you waste your time on
replying some misunderstanding. Tom keep up that!

Now I may also say that good job get partially dirty by your tendency to
reply advanced research topics you fail to understand.

All your postings about advanced research topics i have revised here [#]
and in spr deserve a concise

"Yours is a statement of profound ignorance in all of its parts."
--- Uncle Al to Tom Roberts in sci.physics.research Feb 2008


[#] Your recent evaluation of Chubykalo and Vlaev, or your posting about
history of relativity for instance.

--
http://canonicalscience.org/en/misce...guidelines.txt

[This replies to "Koobee Wublee", Steve Carlip, and Tom Roberts.]


"Koobee Wublee" writes:

[Wublee]: Claiming the speed of gravity exceeding the speed of light in
free space violates relative simultaneity as demanded by the Lorentz
transform and thus SR. Since GR is built on top of SR, GR is falsified in
the process.

Special relativity (SR) has now been falsified in favor of Lorentzian
relativity (LR). See Ref. [1] at end for a primer on LR. The main reasons
for this replacement were published in Ref. [2], and boil down to these two:

** the lack of any experiment showing that the same Lorentz transformation
equations work both ways between any two inertial frames as in SR, as
opposed to working just one way (from the local gravitational potential
field to any other inertial frame) as in LR; and

** 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. See Ref. [3].

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.
Changes caused by motion occur only to clocks, not to time, in LR. If we
built a clock bases on the propagation of sound waves in air, then tried to
accelerate that clock past the speed of sound, its rate would obey the
Lorentz transformations (with c = speed of sound) up to speed c. But the
clock would simply cease to function at speeds at or above speed c.

GR is okay because it is actually based on LR, not SR. It uses Lorentz
transformations only in one direction, from the local gravitational
potential field to any other inertial frame. Substituting LR for SR and
leaving the math of GR as is means no more paradoxes, to the relief of
students of physics everywhere.


and Steve Carlip writes:

[Carlip]: There is a rigorous proof, using the full Einstein field
equations (and not just a low-order approximation that can hide the
underlying structure), that gravitational influence propagates at the
speed of light

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.

Then in Ref. [3], Vigier and I carefully showed exactly where in GR the
switch is made from the speed of changes in gravitational potential (c) to
the propagation speed of gravitational force (infinity). Without that
switch, "gravitational influences" of all kinds, including force, would
propagate at speed c; but the theory would then fail to represent
observations in a gross way (spiraling orbits).

However, you already know these statements are correct. So what did you
hope to accomplish for physics by your misleading wording? What you said
about "gravitational influence" is untrue of gravitational force, which as
you well know cannot propagate as slowly as the speed of light.

[Carlip]: If you really "agree[d] with GR as a mathematical theory," the
argument would be over.

Apparently, it would not, because I do agree with GR as a mathematical
theory, but have taken great pains to show (as others before me have done)
that the mathematical theory has more than one physical interpretation; and
that one of those interpretations (the "geometric") has now been falsified
in favor of another (the "field" interpretation). In short, GR as Einstein
taught it is just fine; but much of the post-Einstein evolution of GR has
been unproductive or outright wrong.

It appears that you are so locked into the geometric interpretation that
you equate falsifying it with falsifying the mathematical theory. But that
would mean you never learned GR as Einstein taught it, because he had little
use for the geometric interpretation. He was familiar with celestial
mechanics and how astronomers test GR using observations made in Euclidean
3-space. You could learn much about Einstein's thinking by becoming more
familiar with the basics of celestial mechanics.

At the very least, that effort would also allow us to communicate with a
common lexicon and common definitions. When GR co-opts words such as "force"
and "velocity", and redefines them in 4-space, they preclude the possibility
of communicating with real-world physicists who conduct the relevant
observations and experiments in 3-space. Examples of such communication
failures appear throughout Tom Roberts' messages, such as the one I reply to
next. He seems not to know that the 3-space world still exists.


and Tom Roberts writes:

[Roberts]: Experiments can test theories. They cannot possibly test
interpretations of those theories. This is so because the way an
experiment and a theory are compared is to take the equations of the
theory, apply the experimental setup to them (e.g. as boundary
conditions), and use the equations of the theory to predict (compute) the
values that the experimental detectors measure. Nowhere in that is any
interpretation of the equations used.

You should try comparing theory and observations sometime. Your phrase
"apply the experimental setup to them" is equivalent to adopting an
interpretation of the theory, a particular physical meaning for the symbols
in the equations.

For example, a = GM/r^2 is an equation connection the gravitational
acceleration of a target body (a) to the gravitational mass (GM) of a source
mass and the distance (r) between the two. Many observations confirm this
relation to be correct and complete for most purposes, excepting certain
critical applications. It is obvious to everyone that there is no
propagation delay in this equation. That fact about the equation has at
least two different physical interpretations:

** [field GR] the effect the source mass has on the target body is
instantaneous to the accuracy of the observations; or

** [geometric GR]: The source mass anticipates the future relative position,
velocity, and acceleration of the target body one light-time ahead, then
sends out its influence as if it came from the retarded source instead of
the true source.

There is no question that the first of these two interpretations is
favored by logic and observations.

[Roberts]: The experiments have said NOTHING WHATSOEVER about whether or
not the "geometrical interpretation" [#] of GR is valid. The experiments
have said that the EQUATIONS of GR are valid (for their specific
measurements).

The experiments have only said that what you call the "approximation"
theory is valid. But the approximation theory has infinite force propagation
speed. In fact, the approximation theory looks almost identical to the
equation example I just gave, except for those higher-order terms that are
of no consequence for the "speed of gravity" issue.

[Roberts]: in GR the geometry is DYNAMIC, and this is fundamental to the
theory.

My dictionary says: "dynamics: the branch of mechanics that deals with
motion and the way in which forces produce motion". In the geometric
interpretation of GR, what force initiates 3-space motion for a target body
at rest relative to a source mass?

This is an important question. Please do not evade it.

[TomVF]: "Force" is the time rate of change of (3-space) momentum. ...
orbital motion represents a force by definition of the word.

[Roberts]: That is just plain wrong. Here is how you can see that it is
wrong: try to describe how one could MEASURE the "gravitational force" on
an orbiting satellite. If you cannot do that, you cannot define "force"
this way. And you CLEARLY cannot do it (if anyone had ever done it, GR
would have been unnecessary, irrelevant, and almost certainly wrong).

We observe the satellite's x,y,z coordinates in the
Earth-centered-inertial frame at a succession of times. Two such
measurements determine the satellite's momentum. Additional measurements
yield the time rate of change of that momentum. This is the 3-space force by
definition.

How can you argue with a definition? This is physics 101. Your
understanding of real-world physics seems severely incomplete.

[Roberts]: Note you must measure the force itself, not any geometrical
aspects of the physical situation -- that would be geometry, and you're
claiming this is not geometry.

Now you are playing word games. The example I just gave used flat
Euclidean space, normal proper time, and conventional 3-space forces.
Geometric GR uses curved space-time, coordinate time, and the initiation of
motion without forces. In real-world physics, propagating forces are
carriers with momentum that originated from a source mass and can collide
with a target body and transfer their momentum. In no sense does this use
the notion that "gravity is just geometry". Geometric GR does.

I'm always careful to put in the caveat "3-space" to avoid confusions of
this sort over definitions. You apparently ignored that distinction.

[Roberts]: To test GR, one must use the equations of GR, or a valid
approximation to them, not some cobbled-together equations into which you
put "delayed forces". The linearized GR approximation is well known to
give equations in which propagation delays don't appear.

Again, you seem to be speaking with confidence about a subject where you
have no knowledge. The conversion from solutions to the field equations into
3-space equations of motion (for the purpose of comparing the theory with
observations made in a flat Euclidean 3-space) is accomplished by a lengthy
mathematical process. There are several versions in the literature, the most
famous being that in Ref. [4]. In this *conversion* process, instantaneous
action at a distance is adopted. Propagation delays are never even
considered, let alone entered and later cancelled. This is also evident in
the end equations, which reduce to the Newtonian equations for ordinary
orbital motion in the majority of cases (weak field, low velocity). As even
you admit, the Newtonian equations (necessarily) have infinite gravity
propagation speed. There are no propagation delays at any order in these
3-space relativistic equations of motion.

And these are the equations used to test GR. I had no hand in
"cobbling-together" these equations. Yet they are just as "instantaneous
action at a distance" as is a = GM/r^2. In the weak-field, low-velocity
cases such as most solar system orbits, these equations reduce to a =
GM/r^2, with gravity propagating at infinite speed. And this has nothing to
do with "approximations". Speed of light propagation for gravity fails to
work by a gross amount even in weak-field, low-velocity cases.

[Roberts]: Even standing on a bathroom scale does not measure
"gravitational force": it CLEARLY measures an UPWARD force on your body
and a downward force on the floor, neither of which can possibly be the
attractive force of gravity.

The downward force is most definitely the force of gravity, as can
readily be verified by raising the person slightly above the floor and
releasing him. It is cancelled by the upward force of the floor.

We are now talking past one another. I am familiar with the "new-speak"
way of redefining common terms in relativity so as to make certain claims
true, such as "gravity is not a force". Again, I am clear in my writing
about what definitions I am using. In order to compare theory to
observations made in flat Euclidean 3-space, GR's predictions must likewise
be converted to flat, Euclidean 3-space. Then we can describe and compare
the two interpretations of GR entirely in this flat, Euclidean 3-space where
forces are the time rate of change of 3-space momentum, velocity is the time
rate of change of position, acceleration is the time rate of change of
velocity, and classical definitions are in full force and effect.

Without doing that, you wouldn't have any clue what the equations of GR
say about orbital motion in real-world physics. -|Tom|-


REFERENCES:

[1] http://metaresearch.org/cosmology/gr....asp#_ednref10

[2] "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).

[3] "The speed of gravity - What the experiments say", T. Van Flandern,
Phys.Lett.A 250, 1-11 (1998); also at
http://metaresearch.org/cosmology/speed_of_gravity.asp.

[4] Einstein, A., Infeld, L., and Hoffmann, B., "The gravitational equations
and the problem of motion", Ann.Math. 39:65-100 (1938).


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

Tom Van Flandern wrote in message

[This replies to "Koobee Wublee", Steve Carlip, and Tom Roberts.]


"Koobee Wublee" writes:

[Wublee]: Claiming the speed of gravity exceeding the speed of light in
free space violates relative simultaneity as demanded by the Lorentz
transform and thus SR. Since GR is built on top of SR, GR is falsified in
the process.

Special relativity (SR) has now been falsified in favor of Lorentzian
relativity (LR). See Ref. [1] at end for a primer on LR:

Ref [1]:
http://metaresearch.org/solar%20syst...iles/proof.asp

Dirk Vdm

On Tue, 15 Apr 2008 22:30:46 +1200, Juan R. González-Álvarez wrote
(in article ):

Tom Roberts wrote on Mon, 14 Apr 2008 21:06:09 -0500:

Juan R. González-�lvarez wrote:
Tom Roberts wrote on Mon, 14 Apr 2008 14:30:05 +0000:
Don't evade the challenge, use whatever expression you wish. Use
whatever definition of "gravitational force" you wish. But be sure to
meet the challenge: describe how to MEASURE the "gravitational FORCE"
on an orbiting satellite, not any indirect or model-dependent
implications of it (such as orbit parameters, which are geometrical,
not any sort of force).

Excuses excuses excuses...

Yes, that's all you give. Please stop with the excuses and answer the
challenge.

Summarizing, you did a strong statement about the gravitational force
(experimental physicists, astronomers enginners are measuring) but you
show unable to write the expression for the force.

· Replying stuff you never studied was your first mistake.

Then you offered us an generic 'argument' (you believed) about why
coordinate dependence of orbits invalidate existence of a physical force,
but in your ignorance of those research topics, you faield to see that
your argument does not apply to theories where the computed (and measured)
gravitational force is coordinate independent (thus not an artifact of
the coordinates choosen).

· Taking too seriously the geometrical approach to gravity was your
second mistake.

Game over.

YOU haven't even started to "play". But this is not a "game", it is a
serious question for you -- why do you think that "gravitational force"
can be measured, and if so, how?

The time of gamming on this newsgroup passed away and i am not longer
reading threads here. Of course, I continue reading spr and spf.


You make bold statements without any explanation, you leave the newsgroup
when challenged on anything and you avoid answering Tom's question. You call
yourself a physicist?

** Posted from http://www.teranews.com **

On Apr 15, 12:42 pm, "Tom Van Flandern" wrote:

"Koobee Wublee" writes:
[Wublee]: Claiming the speed of gravity exceeding the speed of light in
free space violates relative simultaneity as demanded by the Lorentz
transform and thus SR. Since GR is built on top of SR, GR is falsified in
the process.

Special relativity (SR) has now been falsified in favor of Lorentzian
relativity (LR). See Ref. [1] at end for a primer on LR. The main reasons
for this replacement were published in Ref. [2], and boil down to these two:

REFERENCES:

[1]http://metaresearch.org/cosmology/gravity/LR.asp#_ednref10

Galilean transform (GT):

** dt' = dt
** dx' = dx - v dt
** dy' = dy
** dz' = dz

** dt = dt'
** dx = dx' + v dt
** dy = dy'
** dz = dz'

Lorentzian transform (LR):

** dt' = dt / sqrt(1 - v^2 / c^2)
** dx' = dx
** dy' = dy
** dz' = dz

Lorentz transform (SR):

** dt' = (dt - v dx / c^2) / sqrt(1 - v^2 / c^2)
** dx' = (dx - v dt) / sqrt(1 - v^2 / c^2)
** dy' = dy
** dz' = dz

** dt = (dt' + v dx' / c^2) / sqrt(1 - v^2 / c^2)
** dx = (dx' + v dt') / sqrt(1 - v^2 / c^2)
** dy = dy'
** dz = dz'

As you have correctly pointed out, LR does not manifest the twin's
paradox. However, it manifests the time dilation. In doing so, it
does not satisfy the principle of relativity.

At low speed v, SR reduces to GT, but LR does not. Thus, LR must be
wrong.

The following is a simple way of writing down all the equations of SR.

c^2 dt'^2 - dx'^2 - dy'^2 - dz'^2 = c^2 dt^2 - dx^2 - dy^2 - dz^2

Or

ds^2 = c^2 dt^2 - dx^2 - dy^2 - dz^2

Writing down all the equations of LR into one concise equation, you
have

c^2 dt'^2 - dx'^2 - dy'^2 - dz'^2 = c^2 dt^2 / (1 - v^2 / c^2) - dx^2
- dy^2 - dz^2

Or

ds^2 = c^2 dt^2 / (1 - v^2 / c^2) - dx^2 - dy^2 - dz^2

There is no solution to the field equations that would satisfy your
flat spacetime.

These are very serious flaws to your LR.

LR represents a pile of nonsense just like SR that you've pooh-poohed
and GR that you've embraced. shrug

What does the mentioned link has to do with this discussion?

On 15 abr, 17:15, "Dirk Van de moortel" dirkvandemoor...@ThankS-NO-
SperM.hotmail.com wrote:
Tom Van wrote in message
*

[This replies to "Koobee Wublee", Steve Carlip, and Tom Roberts.]

"Koobee Wublee" writes:

[Wublee]: Claiming the speed of gravity exceeding the speed of light in
free space violates relative simultaneity as demanded by the Lorentz
transform and thus SR. Since GR is built on top of SR, GR is falsified in
the process.

* *Special relativity (SR) has now been falsified in favor of Lorentzian
relativity (LR). See Ref. [1] at end for a primer on LR:

Ref *[1]:
*http://metaresearch.org/solar%20syst...iles/proof.asp

Dirk Vdm

Prime Mover wrote in message

On 15 abr, 17:15, "Dirk Van de moortel" dirkvandemoor...@ThankS-NO-
SperM.hotmail.com wrote:
Tom Van wrote in message


[This replies to "Koobee Wublee", Steve Carlip, and Tom Roberts.]

"Koobee Wublee" writes:

[Wublee]: Claiming the speed of gravity exceeding the speed of light in
free space violates relative simultaneity as demanded by the Lorentz
transform and thus SR. Since GR is built on top of SR, GR is falsified in
the process.

Special relativity (SR) has now been falsified in favor of Lorentzian
relativity (LR). See Ref. [1] at end for a primer on LR:

Ref [1]:
http://metaresearch.org/solar%20syst...iles/proof.asp

Dirk Vdm

What does the mentioned link has to do with this discussion?

Fraud, mental condition, incompetence... take your pick.

Dirk Vdm

As Tom Van Flander has said, gravitational potential and gravitational
force are
two distinct concepts and as such their speeds does not have to be the
same.
As many published experiments have demonstrated, gravitational forces
can not possibly
propagate at c. I consider this as a scientific fact, indeed.

It is also true that geometric GR is concerned with gravitational
potential only and that
disturbances in the gravitational potential propagates with speed
equal to c.

In fact, these are such a clear statements and concepts that I am
impressed that there
is any room for discussion on this issue.