Is Length Contraction in SR physical??
in [Relativity]
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From: "Juan R." González-Álvarez on 7 Feb 2010 08:22 Tom Roberts wrote on Fri, 05 Feb 2010 16:06:39 -0600: > Juan R. González-Álvarez wrote: >> Tom Roberts wrote on Thu, 04 Feb 2010 22:54:29 -0600: >>> No. How could arbitrary human choices of coordinates possibly affect >>> the physical phenomena that underlie the things one measures? >> >> ^^^ Here is the origin of your misunderstanding :-D > > How so? > > That is, please explain how choice of coordinates does affect physical > phenomena. In the process you'll have to explain how and why every > physical theory we have and every physics textbook is wrong.... Textbooks, handbooks, and the scientific bodies as IUPAC, IUPAP, do not support your own petit definitions and beliefs. There is available several standard textbooks on relativity explaining how length and kinetic energy are physical quantities, in despite of your invalid claims. I have given to you some literature, including NIST links to standard definition of physical quantity and their example of lenght as physical quantity. I have also explained to you how bodies as IUPAC-IUPAP recomend the use of symbols E_k, K, and T to denote the physical quantity named kinetic energy. I have also cited standard textbook giving T for special relativity... Please stop this crackpot behavior :-D -- http://www.canonicalscience.org/ BLOG: http://www.canonicalscience.org/en/publicationzone/canonicalsciencetoday/canonicalsciencetoday.html
From: "Juan R." González-Álvarez on 7 Feb 2010 08:24 Tom Roberts wrote on Fri, 05 Feb 2010 16:09:33 -0600: > Juan R. González-Álvarez wrote: >> Tom Roberts wrote on Thu, 04 Feb 2010 22:47:11 -0600: >>> My point is: for a given object its length might be measured in some >>> frame as dx, and in another frame as dx'. But any valid physical >>> theory will not use EITHER dx or dx'; instead it will use invariants, >>> such as dL, defined as the 4-vector representing the displacement from >>> one end of the object to the other at a given event (position along >>> its trajectory in space-time). >> >> That is not true. > > So give an argument or counterexample. Textbooks, handbooks, and the scientific bodies as IUPAC, IUPAP, do not support your own petit definitions and beliefs. There is available several standard textbooks on relativity explaining how length and kinetic energy are physical quantities, in despite of your invalid claims. I have given to you some literature, including NIST links to standard definition of physical quantity and their example of lenght as physical quantity. I have also explained to you how bodies as IUPAC-IUPAP recomend the use of symbols E_k, K, and T to denote the physical quantity named kinetic energy. I have also cited standard textbook giving T for special relativity... You do not understand the PoR, neither what a measurement is, neither how physics is actually done. Please stop your crackpot behavior :-D -- http://www.canonicalscience.org/ BLOG: http://www.canonicalscience.org/en/publicationzone/canonicalsciencetoday/canonicalsciencetoday.html
From: kenseto on 7 Feb 2010 08:34 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? I ask this question because that's what I think SR says.
From: kenseto on 7 Feb 2010 08:39 On Feb 7, 12:55 am, mpalenik <markpale...(a)gmail.com> wrote: > 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. No the correct SR prediction is that the geometric projection of the car onto your frame is shorter. This is not material or physical contraction as you inferred above.
From: kenseto on 7 Feb 2010 08:52
On Feb 7, 4:11 am, mpalenik <markpale...(a)gmail.com> wrote: > On Feb 7, 4:05 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 7 Feb, 05:55, mpalenik <markpale...(a)gmail.com> wrote: > > > > 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. > > > Indeed. I don't totally rule out physical length contraction, but I > > would require a physical, classical, explanation first. I simply don't > > accept the argument of "rotation into time".- Hide quoted text - > > > - Show quoted text - > > Whether you choose to accept it or not, that is the correct > explanation. There is no other physical explanation for what's > happening. Sure there is other physical explanation as follows: 1. The observer assumes that the light path length of his meter stick is the same as its physical length....namely one meter long. 2. The observer predicts the light path length of a moving meter stick is contracted by a factor of 1/gamma. 3. In the case of the pole and the barn scenario the contracted light path length of the pole can fit into the physical length of the barn. 4. Notice that this does not mean that the physical length of the pole can fit into the barn with both doors close simultaneously. 5. This explanation avoids all the paradoxes of SR. 6. This concept is included in a new theory of relativity called Improved Relativty Theory (IRT). IRT is available in the following link: http://www.modelmechanics.org/2008irt.dtg.pdf Ken Seto >This is the entire point of the visual exercise that I've > posted. It's to get you to see that length contraction is a geometric > effect related to rotation. There's no other way to describe it. Can > you at least admit that a rotation in time would produce length > contraction and the differences in simultanaity described by SR? If > so, then the only reason you have to believe that it isn't true is > because you don't like it. That's not being scientific at all. |