Is Length Contraction in SR physical??
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From: PD on 8 Feb 2010 11:40 On Feb 8, 4:20 am, Ste <ste_ro...(a)hotmail.com> wrote: > > No I haven't had anything explained to me in a way that I understand. > Indeed, discussions here have predominantly been of either a personal > or a philosophical nature, with hardly any physics discussed by > reference to coherent argument and compelling evidence. > I'm sorry, but you've already declared that what you would find coherent and compelling would be strictly limited to that which YOU consider "physical" and classical, and that furthermore, experimental evidence is sufficiently removed from what you consider "reality" that you would not be dissuaded from that position by dint of experimental evidence. Thus you have insulated yourself from having your opinion changed in any way. Your expectation that physicists owe you a coherent and compelling argument or evidence is voided by obstinacy. And you were wondering why Ken Seto is mocked after doing that same behavior for 15 years? Are you game for getting there much more quickly?
From: PD on 8 Feb 2010 11:42 On Feb 7, 7:34 am, kenseto <kens...(a)erinet.com> wrote: > On Feb 6, 10:57 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 6, 9:02 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 6 Feb, 17:16, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 5, 8:14 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > On 5 Feb, 16:00, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Feb 4, 9:57 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > On 5 Feb, 02:48, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > > > > > > > wrote: > > > > > > > > > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > > > > > > > >news:3979bca1-a35e-4399-bc71-75d2fc680757(a)21g2000yqj.googlegroups.com... > > > > > > > > On 5 Feb, 01:12, artful <artful...(a)hotmail.com> wrote: > > > > > > > > > > On Feb 5, 11:49 am, kenseto <kens...(a)erinet.com> wrote: > > > > > > > > > > > On Feb 4, 6:04 pm, mpalenik <markpale...(a)gmail.com> wrote: > > > > > > > > > > > > On Feb 4, 5:59 pm, "kens...(a)erinet.com" <kens...(a)erinet.com> wrote: > > > > > > > > > > > > > It it does violate the PoR. You made the contradcictory claims that > > > > > > > > > > > > the pole can fit into the barn physically (materially) an at the > > > > > > > > > > > > same > > > > > > > > > > > > time you claim that the pole cannot fit into the barn physically > > > > > > > > > > > > (materially)......that a violation of the PoR. > > > > > > > > > > > > No. The doors are not closed simultaneously in the pole's frame, nor > > > > > > > > > > > are the two ends of the pole simultaneously in the barn in the pole's > > > > > > > > > > > reference frame. In the barn's frame, the two ends of the pole are in > > > > > > > > > > > the barn simultaneously and the doors shut simultaneously. In the > > > > > > > > > > > pole's frame, the two ends of the pole are in the barn at different > > > > > > > > > > > times and the doors shut at different times. > > > > > > > > > > > Sigh..You are making the contradictory claims: > > > > > > > > > > 1. The pole can fit into the barn with both doors close > > > > > > > > > > simultaneously. > > > > > > > > > > In the frame of the barn > > > > > > > > > > > 2. The pole cannot fit into the barn with both doors close > > > > > > > > > > simultaneously. > > > > > > > > > > In the frame of the pole > > > > > > > > > > Two different meanings for 'simultaneously'. So they are not > > > > > > > > > contradictory > > > > > > > > > > You really are not very good at thinking or arguing logically. > > > > > > > > > He seems perfectly reasonable to me. > > > > > > > > > He's saying that, if one stands in the middle of the barn equidistant > > > > > > > > from the doors on each side, and one closes the doors simultaneously > > > > > > > > (i.e. what I would call "absolutely simultaneously", but which for > > > > > > > > conveience we'll say "simultaneous according to an observer standing > > > > > > > > equidistant from each door), then is it possible that both doors can > > > > > > > > appear closed while the ladder is observed to be inside the barn. > > > > > > > > > It's a simple question, and the answer is "no!". > > > > > > > > > ______________________________ > > > > > > > > Its a simple question, and the answer is "yes". It is quite easy to devise > > > > > > > > an inertial frame in which the doors both appear closed and the ladder is > > > > > > > > fully contained in the barn. > > > > > > > > The question wasn't whether "an inertial frame can be devised....". > > > > > > > Even I can think of situations where it would *appear* that the ladder > > > > > > > was inside and both doors closed. The question is whether this is an > > > > > > > artefact of observation, or whether the ladder is actually inside with > > > > > > > both doors closed. The answer remains "no, the ladder does not fit > > > > > > > inside with both doors closed". > > > > > > > There is a simple test. > > > > > > We can determine whether the doors closed simultaneously. We do this > > > > > > using the test of simultaneity I indicated to you above: > > > > > > 1. Have the door-closings generate signals that travel at identical > > > > > > speeds from either event. > > > > > > 2. Have a detector positioned at equal distance from the barn doors. > > > > > > 3. If the detector receives the signals from the barn door-closings at > > > > > > the same time, then the two doors closed simultaneously unambiguously. > > > > > > You and I have agreed on this procedure. > > > > > > If the detector is stationary, then yes we agree that this determines > > > > > simultaneity. > > > > > > > Secondly, we can determine whether any part of the pole was outside > > > > > > the barn when those doors were closed by looking for the marks the > > > > > > ends of the pole would have made on the door. In the absence of those > > > > > > marks, we can safely conclude that the entire pole was inside the barn > > > > > > at the time the doors were closed. > > > > > > Agreed. I would expect this test is definitive, were it possible to > > > > > carry out. > > > > > And this has been tested in equivalent experiment. Documented. > > > > Has it really? Which experiment was that, because my sources say that > > > length contraction has *never* been experimentally observed. > > > I already told you the answer to that. Please look again. > > > > > Seto does not read experimental papers, because he finds them > > > > confusing. So instead he believes what makes sense to him, rather than > > > > letting experimental results tell him something different. > > > > You have to concede at least the possibility Paul that the reason Ken > > > finds them confusing, and so do I, is because *we* can see that they > > > rest on certain assumptions. That is, assumptions that you've > > > internalised, and assumptions which me and Ken reject. > > > In Seto's case, it has more to do with thinking that SR says something > > it does not. I haven't yet figured out whether you are in the same > > boat. > > The only assumptions I make are those that have testable consequences. > > Which ones of those do you think I have that you reject? > > So are you saying that SR doesn't say that the pole can be completely > inside the barn with both doors close simultaneously? SR *certainly* does not say that this statement holds true in both barn frame and pole frame. If you thought it did, then you never understood what SR says. > I ask this > question because that's what I think SR says. You are wrong about that.
From: PD on 8 Feb 2010 11:47 On Feb 8, 7:29 am, Ste <ste_ro...(a)hotmail.com> wrote: > > Minkowski spacetime is a *mathematical* explanation, not a physical > one. What is interesting about this remark is that you consider physics to be the study of the material world, and by "material" you mean to include matter, the space in which matter resides, and all other manner of things in the universe. Thus the nature of space appears to be in the bailiwick of the physical explanations provided by physics, and yet somehow the structure of that space is not physical but mathematical to you. Does this not seem oxymoronic to you? PD
From: PD on 8 Feb 2010 11:57 On Feb 8, 8:10 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 8 Feb, 13:38, mpalenik <markpale...(a)gmail.com> wrote: > > > > > On Feb 8, 8:29 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 8 Feb, 12:36, mpalenik <markpale...(a)gmail.com> wrote: > > > > > On Feb 8, 7:27 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > Indeed, but in any event that remains to be experimentally verified > > > > > and physically explained. > > > > > The physical explanation is the Minkowskian geometry of spacetime > > > > which you have only ruled out because you don't like it. > > > > Minkowski spacetime is a *mathematical* explanation, not a physical > > > one. I dare say that a physical model can be built and explained with > > > plasticine, without any recourse to maths to explain the conceptual > > > foundations. > > > The geometry of the universe is the explanation, just like how the > > geometry for the universe is the explanation for why a ladder gets > > shorter in the x direction if you rotate it. There's nothing more to > > it than that. If you think there's more to a ladder getting shorter > > when you rotate it, I'd love to hear your *physical* explanation for > > why a ladder gets shorter when you rotate it. > > Indeed. The physical explanation for "why a ladder gets shorter when > you rotate it spatially" is that it apparently *doesn't* get shorter. > Experience suggests that the ladder remains the same physical length > no matter what orientation it takes in space. No, it DOES get shorter. Remember there are at least two lengths involved here, both of which are physical. One is the distance between the endpoints of the ladder in the plane of the doorway. That is clearly a physical distance and one that we would ascribe to a length, because it is the distance between two endpoints. The fact that this changes with ladder orientation does not change that fact. What you are saying is that intuition tells you that there is *another* length which does not change with ladder orientation, and that is certainly correct. The mistake you make is saying that it is THIS quantity that is called length and the other is not a length, because it does not meet your invariance criterion. Sorry, but that is an artificial criterion with no physical basis other than your own preference. Now, in the case of relatively moving frames, what is established through experimental evidence (some of it not as direct as you'd like) is that the quantity that we at one time THOUGHT was invariant (that is, the thing we write sometimes as X^2 + Y^2 + Z^2) turns out to be not invariant. This doesn't make it not a length. It is certainly what we have always attributed to a length, regardless of the fact that it turns out to be not invariant. What is also true is that there is a space-time quantity (the thing we'd write sometimes as X^2+Y^2+Z^2-(T/ c)^2) that *is* invariant, but that's not really what we'd call a length anymore because of the time admixture. > The problem only arises > when you try to quantify the length of the ladder geometrically, at > which point it's measured length appears to change with orientation > relative to different axes. > > But the point is that geometry was devised to describe the real world > mathematically. It did not happen the other way around, where the real > world was devised to allow geometry to work. The fact is that any > mathematical model must appeal to physical reality in some way or > another. In some approximation, yes. > > > > > Regardless, you can't even have modified length contractions and claim > > > > that your theory is mathematically equivalent to SR. To be > > > > equivalent, your theory must reproduce the exact same length > > > > contractions that SR predicts. > > > > To be honest, I'm not really that concerned about what is > > > mathematically predicted. I'm more interested in ascertaining the > > > physical explanation for the phenomena in SR, and as yet I have not > > > really turned my mind to the question of how length contraction, if > > > indeed it exists, could occur. > > > If you come up with an explanation but it predicts a different length > > than SR predicts, then you have not given a physical explanation for > > SR. You have given a physical explanation for something else. > > It doesn't really matter. You seem to be placing a great deal of > strain on whether what I'm predicting correlates with the predictions > of SR. My argument is that what I'm predicting correlates with all > observed effects of SR, and reserves judgment for now on the > unobserved effects. > > And as I said, my main concern is to clarify the physical basis of > relativistic effects, and certainly the prevalent interpretation of SR > at the moment, where 'c' is in some way physically constant in all > reference frames is, obviously, not physically possible - and so the > challenge is to explain and clarify why it may be *measured* to be > constant, while in fact not being physically constant at all.
From: PD on 8 Feb 2010 12:01
On Feb 6, 11:48 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 7 Feb, 04:02, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 6, 9:19 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 6 Feb, 20:17, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 5, 8:16 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > On 5 Feb, 16:02, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Feb 4, 8:16 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > On 5 Feb, 00:49, kenseto <kens...(a)erinet.com> wrote: > > > > > > > > > On Feb 4, 6:04 pm, mpalenik <markpale...(a)gmail.com> wrote: > > > > > > > > > > On Feb 4, 5:59 pm, "kens...(a)erinet.com" <kens...(a)erinet..com> wrote: > > > > > > > > > > > It it does violate the PoR. You made the contradcictory claims that > > > > > > > > > > the pole can fit into the barn physically (materially) an at the same > > > > > > > > > > time you claim that the pole cannot fit into the barn physically > > > > > > > > > > (materially)......that a violation of the PoR. > > > > > > > > > > No. The doors are not closed simultaneously in the pole's frame, nor > > > > > > > > > are the two ends of the pole simultaneously in the barn in the pole's > > > > > > > > > reference frame. In the barn's frame, the two ends of the pole are in > > > > > > > > > the barn simultaneously and the doors shut simultaneously.. In the > > > > > > > > > pole's frame, the two ends of the pole are in the barn at different > > > > > > > > > times and the doors shut at different times. > > > > > > > > > Sigh..You are making the contradictory claims: > > > > > > > > 1. The pole can fit into the barn with both doors close > > > > > > > > simultaneously. > > > > > > > > 2. The pole cannot fit into the barn with both doors close > > > > > > > > simultaneously. > > > > > > > > Take comfort Ken that at least there's someone here who understands > > > > > > > your simple questions. > > > > > > > So far it appears that there are at least two people confused and > > > > > > incredulous. > > > > > > Ken has been confused about this for 15 years. We'll soon see whether > > > > > > you can be unconfused at the rate that most freshman students become > > > > > > unconfused about it. > > > > > > I don't know Ken's past history, but certainly he seems to be asking a > > > > > fairly reasonable questions this time - and judging by the responses, > > > > > it's a question that children get taught not to ask! > > > > > When Ken started asking these questions 15 years ago, they were > > > > reasonable questions. When after a couple of years it was clear he was > > > > not listening to the answers given to his questions, the tone of the > > > > responses became a little different. > > > > Well I can assure you I wouldn't tolerate this crowd for 15 years, but > > > I'm hoping that perhaps I can articulate myself better than Ken and > > > make some progress. If not, then I'll comfort myself with Einstein's > > > words that "the only thing that is infinite is human stupidity". > > > Nice to see you've already established the outcome of this > > conversation. That is, it is not entertained that you will be > > convinced of anything differently than what you now hold. The only > > question is whether you'll convince anyone else, and if not, then it's > > time to attribute that outcome to stupidity? > > Ah, but the difference is I *will* discuss my views, I'll discuss them > on each and every occasion someone expresses a legitimate interest in > discussing them, and I'll generally continue to discuss them until > either one of us changes our views, or until the other person gets > tired. But you've already established that it won't be you that might change your views. As for your insistence that you should be able to expect an education suitable for the "ordinary man" at the hand of physicists on a newsgroup, in order for you to change your views, then I think on that too you will guarantee your own failure. > On the other hand, I won't be in a position of tolerating sheer > dismissive abuse and sarcasm for 15 years. > > Indeed, it's clear to me here that many people's beliefs in relativity > are verging on ideological, and I was quite shocked when I first came > here just how arrogant and unreasonable many posters appear to be, > with many posters seeming to compete only on how emphatically and > frequently they can shout "no!". |