Is Length Contraction in SR physical??
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From: artful on 1 Feb 2010 18:38 On Feb 2, 1:55 am, "kens...(a)erinet.com" <kens...(a)erinet.com> wrote: > Is Length Contraction in SR physical?? Define 'physical' > According the most informed SRian, Tom Roberts, the answer to this > question is NO. I doubt that > 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. No .. it can be MODELLED by geometry > When a moving meter stick rejoins the stay at home > meter stick they will have the same physical length Irrelevant > Furthermore if > length contraction is physically real how come SR does not predict > length expansion? How come something can't be slower than at rest? > Is that becasue SR assumes that the observer is in a > state of absolute rest? No. Just rest relative to himself .. everything else is either also at rest, or has a non-zero speed > So what does it mean when SR says that a moving meter stick is > contracted? That is it measured as shorter (eg if you measure poles by whether they fit inside a barn, then the pole is shorter) > The answer: You wouldn't know > 1. An SR observer assumes that the light path length of his meter > stick is the same as the physical length of his meter stick. Nonsense > 2. Using this standard the light path length of a meter stick moving > wrt an SR observer is shorter than the light path length of the stay > at home meter stick. Why? Because light generated at the front end of > the stick will reach the rear end of the stick sooner for a moving > meter stick (c+v) according to the stay at home SR observer. Totally irrelevant > 3. So according to the SR observer the light path length of a moving > meter stick is as follows: > L' = L_o/gamma. Nonsense > 4. The above interpretation avoids all the paradoxes that arise due > to > the bogus interpretation that a moving meter stick is physically > contracted. There are no paradoxes > However, the above interpretation is incomplete. Why? Because it is nonsense and wrong > Because the > light path length of a meter stick moving wrt the observer may be > longer than the observer's meter stick. In that case the light path > length of such meter stick is calculated as follows: > L' = L_o(gamma) > This interpretation is included in a new theory of relativity called > Improved Relativity Theory (IRT). IRT includes SRT as subset. Which is nonsense > However, > the equations of IRT are valid in all environments, including > gravity. Nonsense is nonsense no matter where you use it > A complete description of IRT is available in the following link:http://www.modelmechanics.org/2008irt.dtg.pdf
From: Tom Roberts on 1 Feb 2010 18:42 Juan R. González-Álvarez wrote: > eric gisse wrote on Mon, 01 Feb 2010 08:08:39 -0800: >> kenseto(a)erinet.com wrote: >>> Is Length Contraction in SR physical?? >> No, just as it has been explained to you repeatedly since the mid 90's. > > From Tom Roberts page: > [... attempt to discredit Eric by quoting my web page] This is a LINGUISTIC issue. When someone asks "Is length contraction in SR physical?", they invariably don't have a definite meaning of "physical" in mind (if they did, they could answer the question themselves). Generally, they would consider a "physical length contraction" to mean that the object ITSELF gets physically shorter. This is manifestly not so in SR. But it is indeed what kenseto has repeatedly failed to understand. From where I sit, Eric was justified in his dismissal of kenseto, but Juan is not justified in this particular attempt to slam Eric. Tom Roberts
From: eric gisse on 1 Feb 2010 11:09 kenseto wrote: [...] > What I am enquiring about are as follows: > 1. Tom Roberts said that length contraction is a geometric projection > effect....that means that length contraction is not physical > contraction. This means that length contraction is only apparent and > not physical. The problem with Tom's approach is that what is > "geometric projection" mean physically??? So 15 years running and you don't understand what 'projection' is? Neat. > 2. OTOH runts of the SRians such as PD asserts that length contraction > is physical....a 80 meter long pole can fit into a 40 meter long barn > with both doors close simultaneously for a very brief period. This > assertion of length contraction is physical. Not even worth articulating why you are wrong. > 3. There seem to be contradictory claims amoung the SRians. Probably because you don't understand any of them. [...]
From: PD on 1 Feb 2010 20:04 On Feb 1, 3:33 pm, kenseto <kens...(a)erinet.com> wrote: > 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. 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. > > > It is this discrepancy that I believe Ken is enquiring about.. > > What I am enquiring about are as follows: > 1. Tom Roberts said that length contraction is a geometric projection > effect....that means that length contraction is not physical > contraction. This means that length contraction is only apparent and > not physical. No, it does NOT mean that. Have you asked Tom whether that's what he means? > The problem with Tom's approach is that what is > "geometric projection" mean physically??? Now it's apparent you don't know WHAT he means. > 2. OTOH runts of the SRians such as PD asserts that length contraction > is physical....a 80 meter long pole can fit into a 40 meter long barn > with both doors close simultaneously for a very brief period. This > assertion of length contraction is physical. That depends on what you mean by "physical". Does it mean that some interaction compressed the rod to make it shorter? No, it does not mean that. The pole STILL fits in the barn without requiring that. > 3. There seem to be contradictory claims amoung the SRians. Not at all. You just don't know what Tom *or* I have been saying to you. You think it means something it doesn't. > > I agree with Tom's premise with a twist. I said that the observer > assumes that the light path length of his meter stick is assumed to be > the physical length of his meter stick. The length contraction formula > is used to determine the light path length of a meter stick moving wrt > the observer. This explanation eliminates all the paradoxes encounter > by the SR assertion that length contraction is physical. > > Ken Seto
From: PD on 1 Feb 2010 20:04
On Feb 1, 2:56 pm, kenseto <kens...(a)erinet.com> wrote: > On Feb 1, 3:25 pm, "Juan R." González-Álvarez > > > > <nowh...(a)canonicalscience.com> wrote: > > eric gisse wrote on Mon, 01 Feb 2010 08:08:39 -0800: > > > > kens...(a)erinet.com wrote: > > > >> Is Length Contraction in SR physical?? > > > > No, just as it has been explained to you repeatedly since the mid 90's. > > > > [...] > > > From Tom Roberts page: > > > "At this time there are no direct tests of length contraction, as > > measuring the length of a moving object to the precision required > > has not been feasible. There is, however, a demonstration that it occurs: > > > A current-carrying wire is observed to be electrically neutral in its > > rest frame, and a nearby charged particle at rest in that frame is > > unaffected by the current. A nearby charged particle that is moving > > parallel to the wire, however, is subject to a magnetic force that is > > related to its speed relative to the wire. If one considers the situation > > in the rest frame of a charge moving with the drift velocity of the > > electrons in the wire, the force is purely electrostatic due to the > > different length contractions of the positive and negative charges in the > > wire (the former are fixed relative to the wire, while the latter are > > mobile with drift velocities of a few mm per second). This approach gives > > the correct quantitative value of the magnetic force in the wire frame." > > Hey idiot this does not illustrate length contraction. Sure it does, to those that can read and comprehend. > > Ken Seto > > > > > P.S: Do you want your new 'brilliant' post to be added to your profile as > > USENET crackpot? :-D > > > P.P.S: Newsgroup sniped by Eric re-added to the reply. > > > --http://www.canonicalscience.org/ > > > BLOG:http://www.canonicalscience.org/en/publicationzone/canonicalscienceto... |