Debunking Nimtz
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From: Tom Roberts on 13 Sep 2007 13:32 Vern wrote: > On Sep 12, 11:40 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: >> A better description is that while I'm holding it the stone does not >> follow a geodesic path because of the upward force exerted by my hand; >> when I release it that force is no longer applied to it, and the stone >> naturally follows the geodesic path determined by its position and >> 4-velocity at the moment of release (remember its 4-velocity is the >> tangent 4-vector to its worldline). That geodesic, of course, >> accelerates downward (using those same coordinates fixed to the surface). > > In your last sentence above, you say that the geodesic accelerates > downward (wrt the surface of the Earth). So then it sounds like you > are saying that the fact that the geodesic is accelerating downward > would be the cause of an object affected by that geodesic moving > downward. No. Modern physics does not use "cause" in that way. Science is the process of constructing MODELS of how the world behaves. The geodesic path is a DESCRIPTION of how the rock moves. Nobody knows what underlying physics process or phenomena "causes" it to behave that way (including those who claim to do so). This is at base a recognition that the only way we humans can think about and discuss the world we inhabit is via MENTAL MODELS of that world. > In the absence of gravity, does this principle mean that an object is > still being moved by the geodesic, or would an object placed in the > geodesic remain motionless? A geodesic path is a description, and is powerless to "move" anything. But it is an accurate description of how a freefalling (small) object does actually move. One does not really "place an object into a geodesic" -- when an object is in freefall it naturally follows a geodesic path, specifically the one that is continuous with its current position and 4-velocity. This is the same as differential equations: the equations describe an infinite set of POTENTIAL behaviors, but the specific behavior of a specific system is determined by the initial conditions (boundary conditions) one uses to solve the equations. The instant my hand releases the stone is no different in this from any other instant along its freefalling trajectory -- that is the key concept of LOCALITY: at each and every point of its existence, the object responds only to the local geometry and forces it experiences; there is no "action at a distance" at all. GR and all of classical physics obeys the concept of locality; it is not fully known whether QM does so or not.... Tom Roberts
From: G. L. Bradford on 14 Sep 2007 05:50 If you went up in level to a galactic light-time coordinate system, where as the inter-galactic observer-traveler your own clock time still reigns. A result of achieving this picture as a separate picture is that you've buried the substrata of each and every galaxy in the [deep] beneath a galactic gravitational surface as effectively as if you had buried it in the microverse. More effectively as a matter of fact. Your relative macroverse no longer includes that substrata at all. You've wiped out all of each and every substrata's highly varying light time coordinates relative to one another, the quanta dynamics of the substrata, in favor of the newly acquired surface level of macroverse. The acquired new and different relative of gravitational "field." Traveling within the galaxy, your coordinate system was highly dynamic light time coordinate dimensionality to go with your clock, rather than purely spatial dimensionality to go with your clock. Practically as soon as you 'surface' the galaxy you revert to that purely spatial dimensionality to go with your clock regarding that galaxy. The previous highly dynamic light time dimensionality almost promptly zeroes out (smears out, smoothes out, flattens out) as if it had never existed in the first place, in the (gravitational) surfacing of the galaxy. It might as well be thought of as having disappeared into a General Relativity predicted (floodlit) 'white hole'. Of course it is "black holes" I understand General Relativity predicts. But the fact of a certain [disappearance of time] inside a gravity field's event horizon -- as observed from outside of it -- is exactly the same between the two. GLB
From: Tom Van Flandern on 21 Sep 2007 02:34 Tom Roberts writes: >> [tvf]: Geometry cannot create 3-space forces. A purely geometric GR would >> contain no dynamics. > [Roberts]: There is no necessity to "create" what you call "3-space > forces". This is physics, and you cannot force your personal desires and > prejudices onto nature. The requirement is that GR construct an accurate > model of the world (including the behavior of objects in it), and it does. Perhaps you have just described the most fundamental difference that exists between mathematicians and "deep reality" physicists. Mathematicians attempt to describe reality with equations. Physicists attempt to describe reality with models involving real, tangible, material entities, usually in the form of particles and waves, with interactions by momentum transfers through contact. For the former group, equations are the end goal. For the latter, understanding "how" and "why" is the end goal, and equations are used strictly for calculations, not insight. As this applies here, in ordinary physics, a body at rest in 3-space cannot begin moving unless a force acts on it. Once it does begin moving, it has acquired new 3-space momentum. The time rate of change of its momentum is the measure of the applied force. Even though relativists prefer to work in 4-space, surely they know enough non-relativistic physics to understand these fundamental concepts. Relativists may not care about such physics fundamentals, but they certainly should not be proposing a reality that violates them because that is the logical equivalent of a miracle. Therefore, using definitions found in any basic physics text, geometry cannot initiate motion; only a force can. And in that sense, a purely geometric GR without forces can have no dynamics because dynamics are defined as "the forces that tend to produce activity and change in any situation". [from Microsoft Encarta dictionary] So using standard definitions of terms, my statement you disputed is correct, and is most definitely not just a matter of personal preference or prejudice. So I hope we are now using the same dictionary and can therefore agree on the validity of these simple statements about basic physics. The fact that "GR is an accurate model of the world" was something we both agreed to at the outset, and is not in question here. But of course I meant the field interpretation of GR with its 3-space forces, and you meant the geometric interpretation. Are you now going to claim that the field interpretation of GR preferred by Einstein is no longer considered to be real GR? Remember, only the field interpretation of GR with its 3-space forces in Euclidean space has been tested by astronomical observations. > [Roberts]: Do you seriously think physicists would accept GR if it did not > accurately describe the behavior of a rock when one drops it? So using > your terminology, the geometry of GR clearly DOES "create 3-space forces". You say "geometry" but you are describing the field interpretation of GR. The geometric interpretation denies that gravity is a force. So in geometric GR, the rock cannot begin to move once it is released because such new motion would be a 3-space force (a change of 3-space momentum) by definition. Put in different words, geometric GR simply describes the motion of the released rock as "following a time-like geodesic", and speaks of that as "simply geometry". And if relativists stopped there and said "that's the way it is", we would have no disagreement. But relativists want to answer the demands of scientists, students, and the public for cause and effect, and for an understanding of why rocks in free fall follow geodesics. Answers to such questions can only come from the real world of 3-space with forces. If geometricists stopped trying to pretend that the real world is not needed, this discussion would be over. But some of us think the real world is important. And in it, gravity is still a classical force, and that force propagates much faster than light in forward time and carries information too. For example, it is non-trivial information that each component of a binary pulsar knows where the other is now, well before its light arrives, even though both accelerated during that light transit time. This exact point about the impotence of geometry was made quite succinctly by Vern in a recent message: "In my opinion, you [Tom Roberts] have never satisfactorily answered [tvf's] claim that in the geometric interpretation a straight line may be a curve, but there is no reason for an object to follow that curve unless it is already moving." Indeed, you have made it clear you have no answer beyond "it just does"! > [Roberts]: if you were to ask any GR expert in the world the question > "What is the essence of GR and how it describes gravity?", do you > seriously think you would get an answer like "Gravity is a 3-space force"??? I know I would because that is what I was taught by experts in relativistic dynamics. But then, you don't consider celestial mechanicians to be relativity experts. So we are back to semantics; i.e., every expert who was taught what you were taught and thinks as you do will agree with you. And vice versa. [shrug] You should recognize a closed club with a vested interest when you see one. Moreover, when reasonable and qualified people try to talk to the closed club members about these matters, e.g. by posting lucid comments in on-going discussions in sci.physics.research, their remarks are excluded. The ignorance of the club members is of the invincible variety. (And that is kind compared with what Nobel Laureate and famed author Richard Feynman had to say about relativists.) > [Roberts]: In GR no energy, momentum, or information can be propagated > faster than c ... Nothing about the field can propagate faster than c. But geometric GR cannot describe reality without 3-space forces, and those forces must propagate faster than c and carry information. So if you are able to consider new things about GR, I have some great news: the speed limit is off! And that is peer-reviewed, published, and undisputed in credible published sources for over five years now. > [Roberts]: this "faster than light propagation" occurs ONLY in certain > coordinate systems, and as nature obviously uses no coordinates, such > coordinate-dependent quantities cannot be valid models of physical > phenomena. [E.g. in locally-inertial coordinates there is no > "gravitational force", so how can it "propagate"???] The propagation speed of gravitational force from the source mass to the target body in the field interpretation of GR is infinite in all 3-space coordinate systems. If there were no 3-space force propagating from the source mass to the target body, 3-space motion could not be initiated. Your statement is about 4-space coordinate systems, and it is an unproved conjecture to assert that nature has more than one time coordinate. For example, if LR has now superseded SR, there is just one universal time in nature. > [Roberts]: Say, instead, that the force vector points toward the current > position of the source, not at its retarded position. ... Now one can > compare this to the predictions of GR, and one finds that those > predictions agree ... But GR does not use retarded partials and gradients when comparing to observations. It uses instantaneous partials and gradients. That is the physical equivalent of adopting infinite force propagation speed because with any finite speed, those partials and gradients would be retarded too. > [Roberts]: the stone simply continues along its geodesic path, and that is > COMPLETELY determined by the geometry at each point. Here, you and other relativists are in denial. The Greenberger-Overhauser experiment clearly showed that, in neutron interferometer experiments, the trajectory was mass-dependent, and therefore was not determined by geometry alone. They concluded this falsified the weak equivalence principle that "gravity is just geometry" (meaning 4-space geometry). >> [Vern]: The field interpretation, on the other hand, requires a medium to >> constitute the field. > [Roberts]: no such medium has been observed, and it must have quite > remarkable and counter-intuitive properties. For instance, with a medium > involved it's not clear how to "propagate instantaneous action at a > distance".... Nor is it clear how such a medium could exert gravitational > forces without itself being affected, and without impeding the motion of > planets (i.e. it has no viscous drag and yet exerts "force" on objects). > No real fluid or material comes anywhere close to having the requisite > properties.... These objections merely reflect that you do not read literature relevant to such issues. All these issues and many more like them have been satisfactorily addressed and solved. See for example these two chapters in "Pushing Gravity: New Perspectives on Le Sage's Theory of Gravitation", M. Edwards, ed., Apeiron Press, Montreal (2002): T. Van Flandern, "Gravity", pp 93-122; and V. Slabinski, "Force, heat and drag in a graviton model", pp 123-128. > [Roberts]: In science, we TEST THEORIES, and GR has been well tested > within the solar system and in a few specific extra-solar systems. The > words related to interpretations of theories are not directly testable. What you call GR, the geometric interpretation, has only been tested once (the Greenberger-Overhauser experiment), and it failed that test. The other "tests of GR" are all astronomical test of the field interpretation and use classical forces in Euclidean 3-space. > [Roberts]: my main disagreement with Van Flandern is his CLAIM to be using > GR, when he manifestly is not doing so. And I also disagree with his > claims of propagation >>c that he thinks are general, but are actually > theory specific and do not apply to GR. Without meaning to put words in your mouth, I read this as saying that you accept that the field interpretation (or something like it) does validly have 3-space forces, makes testable predictions in Euclidean space, and has passed those tests; and that the "gravitational forces" in that theory do indeed propagate FTL. You disagree only that it is GR. Is that a fair and accurate summary of what you just said? If the answer is "yes", I think we're done. The rest is just nomenclature. -|Tom|- Tom Van Flandern - Sequim, WA - see our web site on frontier astronomy research at http://metaresearch.org
From: G. L. Bradford on 21 Sep 2007 07:48 Gravity does not propagate at all. When you realize that physicists will never get rid of its infinities; and when you and others begin to realize the probable actual relationship of gravity (as we currently understand it) to so-called "dark matter and (especially) energy," you should realize then that gravity is the single fundamental force -- having duality as "field" and "fields" -- that defines the [vertical levels in-depth] of an entire possible infinite Universe to, at all, have any such "vertical levels in-depth." The 'inter' in such recognized separate [progressive level] existences as "interplanetary," "interstellar," "intergalactic," and the all inclusive "inter-universe," relates directly to the vertical 'interactivity' of gravity alone. They are gravitational / dark energy levels. And the actual number of potential [levels] is probably not anything like finite (having no actual bottom or top). But of course, ultimately, our always narrow view of the situation will be a [relative] view, finite and, therefore herein, divisive in appearance (gravity | dark energy). Cosmologically there appears to be no straight lines at all where velocity holds against acceleration or deceleration (redundant) for anything having any mass whatsoever except one, "orbit." Therefore "gravity" will shift around here to there to wherever throughout the universe, never reaching absolute zero anywhere as a field (a "gravitational field" always being environmentally present on some level to some degree), but never anywhere...anywhere at all...will gravity "propagate" or in anyway be dependent upon either velocity or the speed of light constant, c. Gravity causes a galaxy such as Andromeda to have a single unit of light-time for the whole entity (GALAXY) entirely separate from every individual component entity's light-time of it. It's components will have individualized times of their own on their level or levels of being...and it will have an individualized time of its own on its own level of being. GLB
From: Tom Roberts on 21 Sep 2007 12:22
Tom Van Flandern wrote: > Tom Roberts writes: >>> [tvf]: Geometry cannot create 3-space forces. A purely geometric GR >>> would contain no dynamics. > >> [Roberts]: There is no necessity to "create" what you call "3-space >> forces". This is physics, and you cannot force your personal desires >> and prejudices onto nature. The requirement is that GR construct an >> accurate model of the world (including the behavior of objects in it), >> and it does. > > Perhaps you have just described the most fundamental difference that > exists between mathematicians and "deep reality" physicists. [...] No. You merely display your ignorance of what SCIENCE is. Today, science recognizes the fact that we humans are inherently limited in what we can do mentally, and ALL we can think about related to the real world are MODELS of that world. Science is the process of creating and evaluating such models. > As this applies here, in ordinary physics, a body at rest in 3-space > cannot begin moving unless a force acts on it. Once it does begin > moving, it has acquired new 3-space momentum. The time rate of change of > its momentum is the measure of the applied force. Even though > relativists prefer to work in 4-space, surely they know enough > non-relativistic physics to understand these fundamental concepts. > Relativists may not care about such physics fundamentals, but they > certainly should not be proposing a reality that violates them because > that is the logical equivalent of a miracle. You merely display your ignorance of GR and its geometry. When projected onto your 3-space, using the Newtonian coordinates you insist on, the connection is the same as the "force" you require. This is not "a miracle", this is just the basic geometry of spaceTIME applied to this physical situation and these particular coordinates. > Therefore, using definitions found in any basic physics text, > geometry cannot initiate motion; This is plain and simply not true. The geometry of GR in spaceTIME can and does "initiate motion" relative to your 3-space, for an appropriate physical situation. I repeat: >> [Roberts]: Do you seriously think physicists would accept GR if it did >> not accurately describe the behavior of a rock when one drops it? So >> using your terminology, the geometry of GR clearly DOES "create >> 3-space forces". > > You say "geometry" but you are describing the field interpretation of > GR. Only because YOU FORCE ME TO DO SO. I put "3-space forces" in quotes to indicate the PUNs involved. The geometrical interpretation of GR is every bit as good an interpretation of the world we inhabit as your field approximation. But the field equation of GR includes more solutions than your field approximation can encompass -- that's why what you call an "interpretation" is really an APPROXIMATION. > The geometric interpretation denies that gravity is a force. You rely on PUNs in everything you write. PUNs that destroy your argument. As I said, when projected onto the Newtonian coordinates you insist on, the connection is a "3-space force". In GR, gravity is not a 4-force, it is a connection (just like centrifugal and other fictitious "forces"). Your inability to distinguish these two VERY DIFFERENT quantities, and your use of the same word for both, indicate how confused you are. >> [Roberts]: if you were to ask any GR expert in the world the question >> "What is the essence of GR and how it describes gravity?", do you >> seriously think you would get an answer like "Gravity is a 3-space > force"??? > > I know I would because that is what I was taught by experts in > relativistic dynamics. You live in a world far removed from GR. Either those experts mentioned the approximation involved and you forgot it in the intervening years, or they are not experts on GR. > But then, you don't consider celestial > mechanicians to be relativity experts. In celestial mechanics, the APPROXIMATION you use is excellent, and is probably used for all computations. THAT DOES NOT MEAN IT IS GR. It is only an APPROXIMATION to GR. <shrug> > But geometric GR > cannot describe reality without 3-space forces, Sure it can! But you don't understand that. This is obviously going nowhere. Tom Roberts |