Is Length Contraction in SR physical??
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From: Ste on 7 Feb 2010 00:38 On 7 Feb, 03:57, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 6, 9:02 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > 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. No it hasn't Paul. The experiment you describe, or anything like it, has not been carried out, and the literature makes this clear that physical length contraction has not been observed experimentally. > > > 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? At least one of the assumptions to which I refer is that observation reflects reality. So if length contraction is observed, it must be "real", but in my view this is as childish as saying you're 12 feet tall simply because you're looking into a curved mirror. As I say, I am quite firmly of the view that SR describes the behaviour of EMR - in other words, it describes what you see with your eyes - and says nothing about physical reality.
From: Ste on 7 Feb 2010 00:48 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. 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!".
From: mpalenik on 7 Feb 2010 00:55 On Feb 7, 12:38 am, Ste <ste_ro...(a)hotmail.com> wrote: > As I say, I am quite firmly of the view that SR describes the > behaviour of EMR - in other words, it describes what you see with your > eyes - and says nothing about physical reality.- Hide quoted text - Respond to my post that has the link to my second picture before you respond to this, but here's something for you to consider. Special relativity predicts that an object will undergo length contraction in its direction of motion. Any observer "at rest" at any location should observe this length contraction. Say that a car drives past you close to the speed of light. You take a picture exactly at the instant when the center of the car is directly in front of you. Since the two ends of the car are equidistant from you, if propagation delay were the only thing going on, you should not see any sort of length contraction in the photograph. But SR still predicts that the car should be contracted in its direction of motion, independant of the location of the observer.
From: Peter Webb on 7 Feb 2010 02:03 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:99fff4ac-8582-42ca-8497-0e50e072399a(a)k19g2000yqc.googlegroups.com... > On 7 Feb, 00:35, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:12c2f6df-085e-4024-ad03-5bd5a7099bb3(a)d37g2000yqa.googlegroups.com... >> >> >> >> >> >> > On 6 Feb, 04:30, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> > wrote: >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >> > Indeed. But understanding the physical nature of these theories is >> >> > necessary for scientific advance. I mean, you can teach any fool to >> >> > follow rules that are already laid down. But the people who are >> >> > coming >> >> > up with the rules need to have genuine understanding. >> >> >> Ohh, you mean insight into what is "really" happening. That is exactly >> >> what >> >> Minkowski did when he pointed out that the time and space >> >> transformations >> >> of >> >> Einstein were exactly the same as a rotation in spacetime of an >> >> invariant >> >> vector, and that explained other stuff like Energy and Momentum. >> >> >> It also provided the basis for the General Theory of Relativity, which >> >> uses >> >> this concept as a base. It provides a link between the two theories >> >> which >> >> does not rely on the mathemetics just happening to work out the same >> >> for >> >> treating SR as a special case of GR. >> >> >> If you want "genuine understanding" of SR, Minkowski space-time is the >> >> second thing you should learn, right after Einstein's algebraic >> >> approach >> >> based on his two axioms. >> >> > I *do* have a genuine understanding already. >> >> I doubt it. If you genuinely understood SR you wouldn't have any problem >> resolving the barn and ladder "paradox". > > I have resolved it, and I gave you your simple answer: *no*, the > ladder does not fit. You are wrong. > > > >> Nor do you seem to understand Minkowski' s geometric arguments. > > Indeed, because I'm more interested in physical reality than geometry. > > > >> If you do >> want a genuine understanding of SR, you will need to learn this. Its >> actually not all that difficult at all; you don't need much maths beyond >> an >> understanding of "imaginary" numbers, its very simple. > > I already do understand what SR describes, but *without* the maths. > That's why I can give you an accurate description of what SR predicts > when you give me examples that I can picture in my head. Obviously you don't understand what SR describes, because you can't accurately describe what happens in the ladder/barn scenario.
From: Peter Webb on 7 Feb 2010 02:08
"Ste" <ste_rose0(a)hotmail.com> wrote in message news:738833f8-3fdc-4c6e-af9c-27816ea3942e(a)y33g2000yqb.googlegroups.com... > On 7 Feb, 03:43, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:86583d1c-3ce6-4d27-b43b-8463952c1d02(a)z41g2000yqz.googlegroups.com... >> On 6 Feb, 10:29, mpalenik <markpale...(a)gmail.com> wrote: >> >> > On Feb 6, 5:01 am, Ste <ste_ro...(a)hotmail.com> wrote: >> >> > > On 6 Feb, 09:23, mpalenik <markpale...(a)gmail.com> wrote: >> >> > > But as I'm saying to you, I think you're confusing an optical effect >> > > with a physical effect. That is, you're confusing *appearances* with >> > > concrete reality. >> >> > What part of this picture do you think is optical? It's *geometrical* >> > it doesn't have anything to do with what you can visibly see. >> >> Don't you realise that SR is about the behaviour of *light* - that is, >> EMR? And SR describes how *observations* made by way of *light* change >> in response to physical circumstances? >> >> ___________________________ >> No. SR says the length is contracted. It is. Doesn't matter if you >> measure >> its length with light waves, neutrinos, or a metre ruler. > > Have you actually tried measuring it with a meter ruler, and *without* > using light? Remember, using your eyes is out of the question - you > have to find a way of measuring that does not involve photons. > > > >> > > > An important point, however, is that neither one of the sets of >> > > > axes >> > > > (either x,t or x',t') is inherantly better than the other. Neither >> > > > set is more correct than the other. >> >> > > Indeed. >> >> > How can you agree with that and claim that the differences in >> > measurement are optical? >> >> Because *that* is what SR is all about - it is about describing the >> behaviour of *light*. >> >> _______________________ >> No. Its not. It describes the behaviour of any particle or object capable >> of >> carrying information (causality). The *only* thing that SR is *not* >> required >> for is light, as the length transforms for ligh waves were already known >> to >> be the Lorentz transformations from solving Maxwell's equations. > > "Information" is a poorly defined term, and once again, SR does not > describe the effects of anything but EMR, and I believe classical > mechanics takes care of all physical reality that is not mediated by > EMR. > > > >> > The differences in measurement are due to >> > the different coordinate systems. It has nothing to do with what you >> > *see* it has to do with how you make your measurements. >> >> It has *everything* to do with what you *see*. >> >> _______________________________ >> What is observed. You don't have to "see it" at all; Einstein's >> transforms >> work in the dark just as well. > > Do they now? What experimental evidence do you have to show that SR > "works" where photons are not involved? I assume you *do* have > evidence, don't you? > > > >> > When one >> > observer measures length, he measures along the x axis. When another >> > observer measures length, he measures along the x' axis. The proper >> > length of the object doesn't change, but the measured length has >> > nothing to do with optics, visibility, or propagation delays. >> >> Of course the measured length has *everything* to do with optics. How >> do you think we usually carry out measurements? >> >> _________________________________ >> Lots of ways. Normally I measure length by puting a ruler next to an >> object. > > And by looking at the readings with your eyes no doubt - so we've gone > back to a measurement mediated by light? > No, I feel the edges with my fingers. Blind people can still measure things. > > >> You put a ruler next to the ladder, you will see it has contracted >> exactly >> per Einstein. > > But in fact we don't see that. > You do see that. > > >> And why do you think the ladder appears the correct size for an >> observer in the x' frame? >> >> ____________________________ >> Without knowing what the x' frame is, I would hazard a guess and say the >> ladder is stationary in that frame. > > Indeed, and are not wondering why the ladder seems just as big when it > is measured optically in that frame? Nothing about measuring optically. Blind people can still measure lengths; light is not required. The ladder will be shorter if it is moving relative to the observer. Not "seems" shorter, or "optically appears" shorter, it *is* shorter in the 3D space in which we measure lengths. |