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Jim:

"Gadfly" is right suggesting that my last post to you would make for a dramatic exit. However, that wasn't so much my intent as to, hopefully, provide you with a "wake up call", if you will.

Now, while your response doesn't show much in the way of evidence of your "awakening", there are, perhaps, a few clarifications I would like to make (even though it may disappoint the "Gadfly").

First, perhaps I was a bit too blunt in using the term "weaseling", and I certainly am sorry for how the use of the term has distracted you. True, I didn't go into how I came to see it this way, but that is only because I didn't, and don't, feel like going through our exchanges in order to make this explicit. I'll leave it to others to judge between me and thee.

Second, after quoting my statement:

I "gravitate" to distinguishing between geodesic vs. non-geodesic motion because it is well defined (determinable, at least in principle) in all cases (regardless of the nature of the curvature, or lack thereof). The only "difficulty of determining in some cases, by observation, whether a body is deviating from geodesic motion" is in terms of experimental accuracy, as with any observational measurement.

you then, apparently, try to suggest I've contradicted myself by quoting:

I’ll quote you from 10/1/2007, where: “one can interpret them in other "reference frames" (general coordinate systems) wherein one will ‘see’ accelerations that one can interpret (admittedly from a standpoint instilled from Newtonian mechanics) as coming from ‘forces’.”

However, there is no contradiction here. While it is true that such may "appear" to be "forces" (from "a standpoint instilled from Newtonian mechanics"), it is still possible to make the distinction (up to experimental accuracy) between geodesic and non-geodesic motion. (Simply try matching the trajectory with a free neutral test particle, for goodness sake.)

Third, you quote me with (my emphasis added):

... there are indeed ways of looking at things such that it is, at least as much as any other inertial (pseudo, "false") "force" may be considered to be a "force". (Note that these "inertial forces" are not related to your "inertial acceleration". ...

With your response being:

I’m sorry, that’s incorrect. (I assume you are referring to centrifugal, centripetal, and Coriolis “forces” – again you’re not being specific.) I’ve pointed this out before and you haven’t responded. All of them are manifestations of force, even though not “forces” themselves, and they can be identified as “my” inertial accelerations from any coordinate system, in a controlled experiment, as inside a box. Gravitation is uniquely different, as I've shown by the behavior of test bodies in a controlled experiment in a box.

This could take a post all by itself. To begin, I would hope that you will recognize that I never made a claim that one would not be able to distinguish between these (and other) various inertial (pseudo, "false") "forces" and other "true" forces (barring extra, compact dimensions that may allow motions that appear to be non-geodesic, from a 4D standpoint, while being geodesic from a more "true" standpoint, if that's the case).

Furthermore, the reason I wasn't "specific" is because there are potentially uncountably many such inertial (pseudo, "false") "forces". This is an aspect of what I have been getting at with my references to being appropriately general: Able to handle all cases, no matter what they may be, or may be called—not limited to some subset of circumstances we may be familiar with on, or near, this rock on which we happen to presently reside.

However, while you are correct that the inertial (pseudo, "false") "forces" you enumerated are, in one sense, brought to our attention due to other forces, and, in another sense, due to our choice in coordinate system ("reference frame")—choosing to use a coordinate system fixed to the surface of this rotating orb upon which we reside. The same can be said about the gravitational "force", as you have stated multiple times. Regardless of the inertial (pseudo, "false") "force" (including gravitation), free neutral test particles will follow geodesics (once released, hence the use of the term "free").

So, no, gravitation is not "uniquely different". It can be placed within the same class as all other inertial (pseudo, "false") "forces". (At least it can, depending on one's definition of the "existence" of a "gravitational field". Which I'll touch on below.)

Actually, I have come to view the way physics is usually taught in introductory (Newtonian) mechanics classes as doing a great disservice to the students. It seams that a great deal of emphasis is given in convincing the students that inertial "forces", like centrifugal and Coriolis "forces", are not "real", "true" forces (they are pseudo, or "false" "forces"), while espousing the gravitational "force" to be a "true force".

I really wouldn't be surprised to find that, perhaps, part of your "railing" against any identification of gravitation with the term "force", in any form or way, may stem from your reaction to such a teaching approach, once you came to understand a different perspective from General Relativity. (I've only been trying to point out that even from a General Relativistic perspective, there is more than one way of looking at things. In no case [short of the geometric approach to all "forces"] does gravitation get "mixed up" with "true forces" the way it does in Newtonian mechanics [due to Newtonian mechanics' misrepresentation of "inertial" reference frames.)

Forth, after quoting me with the following:

Your point 2 looses almost all it's power because it is not general enough. I have tried to help you see how this can be completely generalized (up to a point), depending on how you wish to "define" the "existence" of a "gravitational field". Unfortunately, instead, you have tried to weasel out of definitions. You have refused to learn greater generalizations. You simply don't appear able to move from your comfort zone in the very specialized subset of circumstances you find on and very near this ball of rock we reside upon, while the universe is far more vast and wondrous. (If you desire, I, and others, can help you take off your blinders, but we can't force you.)

you respond with:

I would think that you would justify your charge of “weaseling” by giving some example of the sort of generalization you have in mind, without being asked. ...

Ignoring the "weaseling" issue, I will be glad to accommodate your request, given, as I stated, how you choose to "define" the "existence" of a "gravitational field". Perhaps I may help by suggesting a few possible definitions:

1. One could choose to take the view that the shape (curvature) of spacetime is dynamic, as given by General Relativity, and since this explains gravitation, regardless of the shape spacetime takes, as a result of this dynamics, gravitation, or the "gravitational field" always exists. In this view, it simply makes no sense to talk about any absence of a "gravitational field", even if the dynamics are such that locally, or even globally, the spacetime curvature vanishes (is zero). (Actually, within this view, talking about a non-existent "gravitational field" would be equated with saying one is ignoring the dynamics and "forcing" the shape of spacetime to some specific shape, like the flat spacetime of Special Relativity or Quantum Field Theory.)
2. One could choose to take the view that so long as the spacetime manifold (the place where events exist) cannot be identified with its tangent space (the vector space at each point of the spacetime manifold where direction vectors, and such, "exist"), then a "gravitational field" exists. So the only time a "gravitational field" does not "exist" is when the whole spacetime manifold is flat.
3. One could choose to take the view that the local curvature of spacetime is the "gravitational field". So the "gravitational field" exists, or not, depending on whether the local spacetime is curved. This is determined by whether, or not, the Riemann curvature tensor is non-zero. (The Riemann curvature tensor is the generalization of "tidal forces". I have, earlier, tried to point out how it has just as much a phenomenological means of determination as does geodesic motion [except that it takes more free neutral test particles to fully determine, and if one does not fully determine it, relying on more parochial determinations, like the convergence of geodesics, then one risks a mis-determination of the nature of spacetime].)
4. Or some other definition?

Make the choice, and then we may go on. Get distracted and diverted with other issues and this will go unanswered (unless someone else makes a choice and we leave you behind).

The ball's back in your court, Jim.

David