Is Length Contraction in SR physical??
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From: kenseto on 9 Feb 2010 17:29 On Feb 9, 11:32 am, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 8, 2:58 pm, kenseto <kens...(a)erinet.com> wrote: > > > > > > > On Feb 8, 3:25 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Feb 7, 8:39 am, kenseto <kens...(a)erinet.com> wrote: > > > > > > 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. > > > > > Why should I listen to what you said when you did made sense.?? > > > > Ken, it isn't wise to stop listening to people if you do not > > > understand what they are saying. It would be important in that case to > > > say, "I don't understand what you are saying. Can you explain it > > > differently so I can understand it?" > > > I don't listen to you because you keep on making contradictory claims. > > For example the pole is physically contracted to fit the barn and at > > the same time the pole does not fit into the barn because it is not > > physically contracted. > > Those are not contradictory claims. Yes they are. >Those are different accounts made > in different reference frames. There is no requirement that the > accounts be identical in different reference frames, and therefore > they are not contradictory. They have to agree whether the physical length of the pole can fit into the shorter barn. The physical length cannot fit into the barn is an absolute concept and it is not observer dependent. Ken Seto > > Nor is it contradictory to say that a falling ball has a straight-line > trajectory AND a parabolic trajectory in the same fall. Galileo knew > that. I don't see why you don't understand that.- Hide quoted text - > > - Show quoted text -
From: PD on 9 Feb 2010 17:54 On Feb 9, 4:25 pm, kenseto <kens...(a)erinet.com> wrote: > On Feb 9, 11:30 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Feb 8, 3:09 pm, kenseto <kens...(a)erinet.com> wrote: > > > > On Feb 8, 3:09 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 8, 12:38 pm, kenseto <kens...(a)erinet.com> wrote: > > > > > > On Feb 8, 11:42 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > 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 didn't say that that statement hold true in both barn and pole > > > > > frame. > > > > > Yes, you did. Two days ago you said just this: "The pole observer have > > > > to agree with the barn observer that the pole > > > > is completely inside the barn with both door close simultnaeously." > > > You said: "The pole observer have to agree with the barn observer that > > the pole is completely inside the barn with both door close > > simultnaeously." > > > You THEN said "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. > > > I told you No, SR does NOT say this, and neither does the PoR. > > > You THEN said, "I didn't say that that statement hold true in both > > barn and pole frame." > > I was referring to the obsolete SR interpretation. I disagree with > this old SR interprestion. I agree with Tom Roberts interpretation > that length contraction is not physical. It is the geometric > projection of the physical length of the pole is shorter and this > projection is able to fit into the length of the barn. > SR has not changed, Ken. What Tom is telling you is how SR has described the events for decades. This does not account for your misunderstanding what you've read.
From: PD on 9 Feb 2010 17:56 On Feb 9, 4:29 pm, kenseto <kens...(a)erinet.com> wrote: > On Feb 9, 11:32 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Feb 8, 2:58 pm, kenseto <kens...(a)erinet.com> wrote: > > > > On Feb 8, 3:25 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 7, 8:39 am, kenseto <kens...(a)erinet.com> wrote: > > > > > > > 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. > > > > > > Why should I listen to what you said when you did made sense.?? > > > > > Ken, it isn't wise to stop listening to people if you do not > > > > understand what they are saying. It would be important in that case to > > > > say, "I don't understand what you are saying. Can you explain it > > > > differently so I can understand it?" > > > > I don't listen to you because you keep on making contradictory claims.. > > > For example the pole is physically contracted to fit the barn and at > > > the same time the pole does not fit into the barn because it is not > > > physically contracted. > > > Those are not contradictory claims. > > Yes they are. > > >Those are different accounts made > > in different reference frames. There is no requirement that the > > accounts be identical in different reference frames, and therefore > > they are not contradictory. > > They have to agree whether the physical length of the pole can fit > into the shorter barn. No, they do not. There is no such requirement. > The physical length cannot fit into the barn is > an absolute concept and it is not observer dependent. I'm sorry, Ken, that is just wrong. > > Ken Seto > > > > > > > Nor is it contradictory to say that a falling ball has a straight-line > > trajectory AND a parabolic trajectory in the same fall. Galileo knew > > that. I don't see why you don't understand that. Do you understand what I wrote in this paragraph? Do you see why this is also not a contradiction?
From: Edward Green on 9 Feb 2010 20:00 On Feb 1, 9:55 am, "kens...(a)erinet.com" <kens...(a)erinet.com> wrote: > Is Length Contraction in SR physical?? > According the most informed SRian, Tom Roberts, the answer to this > question is NO. His answer is that length contraction is the geometric > projection effect of the length of a moving meter stick onto the SR > observer's frame. When a moving meter stick rejoins the stay at home > meter stick they will have the same physical length. Furthermore if > length contraction is physically real how come SR does not predict > length expansion? Is that becasue SR assumes that the observer is in a > state of absolute rest? Regarding the ever-popular reality of length contraction, I prefer that annoying point of view that it's certainly real, however much it depends on perspective, because effects involving perspective are real too! He who doubts this should try to move the two meter stick through the one meter wide door without a suitable rotation. He will find that this purely "artificial matter of perspective" reflected in the apparent length of the stick will mean the difference between walking through easily, and bending or breaking the stick. <...> > > Reply to author Forward > > You must Sign in before you can post messages. > To post a message you must first join this group. > Please update your nickname on the subscription settings page before > posting. > You do not have the permission required to post. What are you on about!? This is the open net. I don't need no stinkin' permission to post. ;-)
From: Edward Green on 9 Feb 2010 20:05
On Feb 1, 2:03 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 1 Feb, 17:25, PD <thedraperfam...(a)gmail.com> wrote: > > > > > 2. Secondly, he did NOT say that the length contraction is not > > physical. What he did say is that the word "physical" has an ambiguous > > meaning at best and does not mean what you think it means. What he did > > say is that physics deals with what is MEASURED, and what is measured > > is therefore physical in that sense. It was you and ONLY you that said > > that if it is a geometric effect (which it is), then it CANNOT be > > called a physical effect. Tom did not make that statement. You did. > > I think others will contend that "what is measured" does not > necessarily relate to a physical reality. Good lord, man: what else would it necessarily relate to? > After all, if I have an > elastic meter ruler, and apply various amounts of tension to it, then > the measurement of an object can be changed without any "physical" > change in that object. On the other hand, if the object to be measured > is also elastic, and I apply the same amount of tension to the object > as well as to the meter ruler, then there are "physical" changes even > though there is no change in the measurement. In other words, the output of the measurement process is a function of both the state of the measuring device and of the measured object. Agreed. But both are surely part of "physical reality". If you take my point. > > It is this discrepancy that I believe Ken is enquiring about.. |