BLAMING SPECIAL RELATIVITY?
in [Physics]
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From: Tom Roberts on 13 Jul 2008 01:58 Danny Milano wrote: > [... quote from Einstein] > From this Eric Baird built an entire theoretical structure > about GR without SR ... Which is completely and utterly wrong. GR inherently and intrinsically includes SR: A) as the local limit of any manifold at any point B) as the unique solution to the field equation for a world without any contents and the topology of R^4. > Baird said: > Almost all of the problems and potential problems that > we've identified here with Einstein general theory seem > to be consequences of the theory's incorporation of > special relativity, and its assumption that the > relationships of SR have to apply as a limiting case of > the theory. This is complete nonsense. Without SR there would be no GR; there COULD be no GR. While there are indeed POTENTIAL problems with GR, at present there are NONE related to SR. The experimental support of SR in essentially all non-gravitational contexts is solid and unassailable (except in certain ways by experts blazing a trail toward quantum gravity -- look up "doubly special relativity", but be prepared for advanced math). SR is one of the best-tested theories we have, and within its domain of applicability there is not a single reliable and reproducible experiment which contradicts its predictions. SR and GR are also inflexible theoretically: attempting to modify SR and/or GR is like being "a little bit pregnant" -- there are no simple modifications possible (the experts know this, and take it into account in pursuing QG). Cranks like Baird (and many others around here) simply do not have a clue about how to do physics, or what physics really is. > What do you think? I can't find other researchers working > on GR without SR. How many relativists or even anti-relativists > attempt this? It does not matter what various people think, and it does not matter how many people attempt "this" -- GR inherently and intrinsically includes SR. The structure of a theory is utterly independent of what people might "think". As I have said before: it is amazing how persistent and prolific some cranks are, without much understanding of the basic physics underlying what they attempt to write about. Eric Baird is one of them. Tom Roberts
From: Eric Gisse on 13 Jul 2008 03:00 On Jul 12, 6:51 pm, Danny Milano <milanoda...(a)yahoo.com> wrote: [...] Why do you keep babbling about a particular irrelevant crank ?
From: Danny Milano on 13 Jul 2008 06:17 On Jul 13, 1:58 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > Danny Milano wrote: > > [... quote from Einstein] > > From this Eric Baird built an entire theoretical structure > > about GR without SR ... > > Which is completely and utterly wrong. GR inherently and intrinsically > includes SR: > A) as the local limit of any manifold at any point > B) as the unique solution to the field equation for a world without > any contents and the topology of R^4. > > > Baird said: > > Almost all of the problems and potential problems that > > we've identified here with Einstein general theory seem > > to be consequences of the theory's incorporation of > > special relativity, and its assumption that the > > relationships of SR have to apply as a limiting case of > > the theory. > > This is complete nonsense. Without SR there would be no GR; there COULD > be no GR. > > While there are indeed POTENTIAL problems with GR, at present there are > NONE related to SR. > > The experimental support of SR in essentially all non-gravitational > contexts is solid and unassailable (except in certain ways by experts > blazing a trail toward quantum gravity -- look up "doubly special > relativity", but be prepared for advanced math). SR is one of the > best-tested theories we have, and within its domain of applicability > there is not a single reliable and reproducible experiment which > contradicts its predictions. SR and GR are also inflexible > theoretically: attempting to modify SR and/or GR is like being "a little > bit pregnant" -- there are no simple modifications possible (the experts > know this, and take it into account in pursuing QG). Cranks like Baird > (and many others around here) simply do not have a clue about how to do > physics, or what physics really is. > > > What do you think? I can't find other researchers working > > on GR without SR. How many relativists or even anti-relativists > > attempt this? > > It does not matter what various people think, and it does not matter how > many people attempt "this" -- GR inherently and intrinsically includes > SR. The structure of a theory is utterly independent of what people > might "think". > > As I have said before: it is amazing how persistent and prolific some > cranks are, without much understanding of the basic physics underlying > what they attempt to write about. Eric Baird is one of them. > > Tom Roberts Baird main counterarguments from his website mentioning what went wrong in the development of relativity (he is going for the kill): GR1915 is meant to be a superset of special relativity, with the equations and relationships of SR built into the theory as a limiting case. Although special relativity made a few simplifying assumptions that weren't really appropriate for a general theory of relativity (such as the equivalence of inertial mass without gravitational mass, and the allowance of arbitrarily high concentrations of kinetic energy without curvature), GR1915 nevertheless assumes that the relationships that SR obtained by doing thi s were the correct ones, and that they have to carry over into our shiny new "curved spacetime" theory. When Einstein was designing his general theory, he was trying something very ambitious. As someone who wasn't a professional mathematician, he was trying to produce a curvature based solution where the mathematical "greats" before him had failed. He had the advantage over Nineteenth-Century researchers of having realised that gravity had to bend both space and time, but he'd published that result in 1911, and now he was racing to produce a general theory before someone else beat him to it. He was familiar w ith special relativity, he trusted it, ,rid by declaring that general relativity had to reduce to it, he managed to narrow the options for how his new theory should function without having to start over completely from scratch. Einstein doesn't seem to have demonstrated that general theories must reduce to special relativity, and doesn't seem to have been able to rederive SR's equations of motion in the context of a curved-spacetime model. But by deciding that his general theory would reduce to SR as a matter of design, he made his job slightly easier. "flatness" in classical field theory at small scales The geometrical argument for GR's reduction to SR goes something like this: general relativity describes the shape of the metric as curved, but as we zoom in to examine smaller regions of spacetime, larger-scale curvatures become more difficult to notice. Eventually, if we zoom in arbitrarily far, we find ourselves looking at a section of metric that is arbitrarily flat, and we can then argue that, in this small region that is effectively curvature-free, relativistic geometry must conform to the flat-spacet ime relationships of special relativity. Fair enough. But it doesn't follow from this that a general theory of relativity is compelled to reduce to the physics of SR, unless we can also show that curvature isn't an intrinsic feature of particles and their interactions ... it ignores the possibility that perhaps physics is curvature. If we zoom in so far that curvature effects no longer exist in our selected region, then this might just mean that we've zoomed in too far, and are now studying a region in which no meaningful physics is taking place. The idea of- "intrinsic curvature" would spoil the case for SR being inevitable as physical law. If we were to believe that the massenergy of particles warps spacetime, and that relative motion is expressed as further warpage of spacetime, then by zooming in so far that there is significant curvature in our field of view, our "flat" region would seem to be defined by an absense of any interesting physics The region wouldn't contain any particles with significant relative motion, or any associated gravitomag netic effects, or particles with any relativie motion at all. In fact, it wouldn't contain any particles, period. The limiting case where SR would be geometrically valid would then be the case where there is actually no physics to describe, and as soon as we started including real particles with real energies and rnotion, our "proof" of a reduction to special relativity would fail. , We'd have nothing happening, and nobody to watch it not happening. We'd also not have compelling reason to insist that the principle of relativity had any reason to apply to the "empty" region, because there wouldn't be anything concrete to apply the PoR to: if the principle hypothetically didn't hold in the empty region for observers that didn't exist, we'd probably be none the wiser ... there'd be nothing unusual to see and nobody to notice, and no. one to file a complaint. This would seem to be null phy sics. So, to say that we know that it's a geometrical requirement for general theories to reduce to the physics of SR, for real objects, is equivalent to saying that we know that gravitomagnetism and particulate effects and energy don't warp spacetime in a significant way, and don't play an essential role in the physical interactions between bodies. It's a rejection of geometrodynamic principles. The special theory doesn't seem to emerge from curved-spacetime geometry as physics unless we've already convinced our selves that the SR concept of "the physics of flat spacetime" is valid. The background arena in which inertial physics is enacted may well be flat, but the actions themselves need not be - the flatness of the background "stage scenery" doesn't have to apply to the actors on the stage. It may well be that all physics is geometry. It does not follow that all geometry is physics. WHAT'S WRONG WITH SR SR and Observerspace Explanations of special relativity often emphasise the importance of "observers" and "observations", and this can give the impression that Einstein's special theory is a literal Observerspace theory - that is, that it deals directly with what observers at particular locations should experience. This seems to make a strong case for the idea that the special theory's physical predictions have to apply if the principle of relativity is correct. But this impression wouldn't be entirely accurate. By convention, a perfect observer is Usually supposed to be someone or something that records the experiences that they're presented with, literally, without extrapolation or bias - they try to report their experiences objectively without imposing their own personal belief systems or interpretations onto the data that they collect. An "observationalist" theory will tend to say that what we see to be happening is, for us, what is happening, and if we define our "observers" broadly enough to include solid inanimate bodies and atoms, then our resulting theory of how these objects "see and feel" each other should then tell us something useful about the actual physics of how these bodies interact with each other. But, as James Terrell eventually pointed out (in 1959) this doesn't correspond to the behaviour of "observers" under special relativity. Einstein's special theory insists that inertial observers can extrapolate their own locally-constant speed of light outwards throughout the surrounding region, and can also treat the velocity of light as a global constant, and their observations" are predicted, interpreted and reported in the context of these new beliefs. This reinvention of the act of observation, incorpo rating the assumption of flat spacetime, restricts our relativistic options to the equations of special relativity. The theory does then go on to make specific physical predictions for the effects that should be directly visible according to the theory ... but we have to remember that what an SR observer is supposed to observe isn't necessarily what the theory predicts they should actually be seeing. "non-SR" observerspace approaches Could we try to build a more literal observerspace model than SR? If we try, we immediately run into some odd behaviour. For instance, if we said that the rate of timeflow of an object (for a given observer) was the rate that that observer would see the object to have, then a circle of "stationary" observers surrounding a "moving" object would report different ', observe& values for the object's rate of timeflow depending on their viewing angle - an observer in front of the object would see it ageing more q uickly, and an observer behind it would see it ageing more slowly. We wouldn't be able to use a single value for the object's 11 observed rate of timeflow" according to observers in the same inertial frame, and our more abstract SR logic to do with collections of "observers" and "frames" wouldn't work. If we took this "seen" behaviour literally, we'd have to allow an object's apparent rate of timeflow, to be route-dependent, and by assuming local c-constancy, these "apparent" tirneflow differences would then turn into "apparent" gravitational gradients between the Object and the surrounding observers - the objects motion would appear to have an associated gravitational field. The moving body would seem to be producing something like the "tilted gravitational well" description of section 9.12, we'd not be able to say that the metric stays flat when confronted with masses with significant relative velocity, we'd have ragging and gravitomagnetism as fundamental effects, and we'd be led naturally towards c equivalence principle and the "most general" version of the general principle of relativity. SO, although SR tends to be considered as an observerspace theory, it doesn't fully embrace observerspace principles ... if it had, it would have ended up as a different class of theory, with a different lightspeed propagation model and different equations of motion. Its application of the PoR to "frames" is necessarily one stage removed from direct observation.
From: Daryl McCullough on 13 Jul 2008 07:32 Danny Milano says... > > >Albert Einstein said in Scientific American April 1950: > >"I do not see any reason to assume that.. the principle >of general relativity is restricted to gravitation and >that the rest of physics can be dealt with separately >on the basis of special relativity... I do not think >that such an attitude, although historically >understandable, can be objectively justified. ... In >other words, I do not believe that it is justifiable to >ask: what would physics look like without gravitation?" [stuff deleted] >The special theory isn't compatible with general >relativistic principles, it's not compatible with >gravity, it prevents us from building gravitomagnetism >into the model, and stops us using acoustic metrics. That paragraph is just wrong. Special Relativity is a special case of General Relativity, in the same way that a plane is a special case of a 2-dimensional surface. General Relativity is a generalization of special relativity. -- Daryl McCullough Ithaca, NY
From: Greg Hansen on 13 Jul 2008 07:33
Danny Milano wrote: I'm not going to reply comprehensively, just sniping here and there. > Baird main counterarguments from his website mentioning > what went wrong in the development of relativity (he is > going for the kill): > > GR1915 is meant to be a superset of special relativity, > with the equations and relationships of SR built into > the theory as a limiting case. Although special > relativity made a few simplifying assumptions that > weren't really appropriate for a general theory of > relativity (such as the equivalence of inertial mass > without gravitational mass, and the allowance of > arbitrarily high concentrations of kinetic energy > without curvature), GR1915 nevertheless assumes that > the relationships that SR obtained by doing thi s were > the correct ones, and that they have to carry over into > our shiny new "curved spacetime" theory. Not really. GR is built from its postulates as an independent theory. The postulates of special relativity are the invariant speed of light and the principle of relativity. General relativity adds the qualifier of a locally invariant speed of light, and the equivalence between gravity and acceleration. The general theory reduces to the special theory in flat spacetime because it still has the locally invariant speed of light and the principle of relativity. You can analyze accelerated systems in special relativity. The uniformly accelerating rocket and the rotating disk are the two classic examples. In both cases you get very gravity-like effects, such as the clock in the nose of the rocket running faster than the clock in the tail of the rocket (i.e. gravitational redshifting). But gravity changes in different places, so special relativity can't be a general theory of gravity. > Fair enough. But it doesn't follow from this that a > general theory of relativity is compelled to reduce to > the physics of SR, unless we can also show that > curvature isn't an intrinsic feature of particles and > their interactions ... it ignores the possibility that > perhaps physics is curvature. If we zoom in so far that > curvature effects no longer exist in our selected > region, then this might just mean that we've zoomed in > too far, and are now studying a region in which no > meaningful physics is taking place. > > The idea of- "intrinsic curvature" would spoil the case > for SR being inevitable as physical law. If we were to > believe that the massenergy of particles warps > spacetime, and that relative motion is expressed as Oh, he's adding his own postulate. Well, since interactions between subatomic particles seem described very well by ignoring gravity, I think Baird is beholden to show that *his* theory also reduces to special relativity in that regime. The curvature of general relativity isn't some mysterious influence that's hard to understand-- if there's not enough gravity to worry about, then there's not enough curvature to worry about. If there was enough gravity to worry about, than the repulsive interactions between same-charged particles and the attractive interactions between oppositely charged particles wouldn't be described so well in QED with a single coupling constant, alpha. Or, for that matter, that interactions between macroscopic objects wouldn't be described so well by ignoring gravity. For instance, the gravitational attraction of a cannonball to its target. It takes delicate equipment to measure the gravity between objects of a few kilograms weight. Easy to measure between planets, hard to measure between bowling balls... guess if it's getting more or less important at subatomic scales. > SR and Observerspace > > Explanations of special relativity often emphasise the > importance of "observers" and "observations", and this > can give the impression that Einstein's special theory > is a literal Observerspace theory - that is, that it > deals directly with what observers at particular > locations should experience. This seems to make a > strong case for the idea that the special theory's > physical predictions have to apply if the principle of > relativity is correct. > > But this impression wouldn't be entirely accurate. By > convention, a perfect observer is Usually supposed to > be someone or something that records the experiences > that they're presented with, literally, without > extrapolation or bias - they try to report their > experiences objectively without imposing their own > personal belief systems or interpretations onto the > data that they collect. An "observationalist" theory > will tend to say that what we see to be happening is, > for us, what is happening, and if we define our > "observers" broadly enough to include solid inanimate > bodies and atoms, then our resulting theory of how > these objects "see and feel" each other should then > tell us something useful about the actual physics of > how these bodies interact with each other. > > But, as James Terrell eventually pointed out (in 1959) > this doesn't correspond to the behaviour of "observers" > under special relativity. Einstein's special theory > insists that inertial observers can extrapolate their > own locally-constant speed of light outwards throughout > the surrounding region, In other words, the "intelligent observer" of special relativity makes account of signal propagation times. If he says a clock way over there is running slow, it's not just because the signal is delayed in getting to him, he's already corrected for that. > and can also treat the velocity > of light as a global constant, and their observations" > are predicted, interpreted and reported in the context > of these new beliefs. This reinvention of the act of > observation, I wouldn't call it a reinvention, really. The alternative is that signals travel infinitely fast and need no correction. This works fine when you're using visual observations of, say, the landing of a cannonball. And in an inertial reference frame in special relativity, globally invariant and locally invariant are equivalent. > incorpo rating the assumption of flat > spacetime, restricts our relativistic options to the > equations of special relativity. The theory does then > go on to make specific physical predictions for the > effects that should be directly visible according to > the theory ... but we have to remember that what an SR > observer is supposed to observe isn't necessarily what > the theory predicts they should actually be seeing. The usual predictions assume that events can be recorded locally along a network of rulers by clocks that have been synchronized by a specified process. Transforming that to visible results takes more work. > > "non-SR" observerspace approaches > > Could we try to build a more literal observerspace > model than SR? If we try, we immediately run into some > odd behaviour. For instance, if we said that the rate > of timeflow of an object (for a given observer) was the > rate that that observer would see the object to have, > then a circle of "stationary" observers surrounding a > "moving" object would report different ', observe& > values for the object's rate of timeflow depending on > their viewing angle - an observer in front of the > object would see it ageing more q uickly, and an > observer behind it would see it ageing more slowly. We > wouldn't be able to use a single value for the object's Here's a case in point. Another is that if you consider what a approaching and receding trains "look like", the approaching train would appear shorter because of the difference in signal propagation times from the front of the train and the back, and a receding train would longer. But the length contraction of special relativity is symmetric for approaching and receding objects, and it's assumed that any visual effects are corrected for in the observation. > If we took this "seen" behaviour literally, We don't. Maybe he thinks we do. > equations of motion. Its application of the PoR to > "frames" is necessarily one stage removed from direct > observation. The observer has a state of motion relative to the observed. I'm not sure how Baird thinks he can consider direct observation at all if he doesn't define reference frames that relate the motion of the observer to that of the observed. |