Is Length Contraction in SR physical??
in [Relativity]
|
Prev: Simultaneous events and Einstein's absolute time
Next: New Theory --- The Theory of Quantum Wave Sources
From: kenseto on 1 Feb 2010 20:50 On Feb 1, 6:42 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > Juan R. González-Álvarez 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: > > [... 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. The general public know what physical length means.....the length of a ruler is physical. If you don't like the word physical how about "material" length contraction? In any case you stated above that material length contraction does not occur in SR and I agree with that fully. So I don't know why you accused me of repeatly failed to understand!!!!!! BTW your SR brothers PD and other disagree with you. They insisted that a moving meter stick itself gets physically (materially) shorter. Ken Seto > > 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: kenseto on 1 Feb 2010 21:03 On Feb 1, 6:22 pm, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "kenseto" <kens...(a)erinet.com> wrote in message > > news:b53814cc-0c14-476f-bc2c-a88d5532884e(a)u26g2000yqm.googlegroups.com... > 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. > > _______________________ > No. You are confusing two different sets of co-ordinates. The length > contraction in physical 3D space is real. It can be interpreted as the > projection of a 4-vector (space and time) onto 3D space. The 4D vector > doesn't change its magnitude, but the 3D projection (which is what we > physically measure) certainly does. I suggest that you go argue with your SR brother Tom Roberts. He said: "Generally, they would consider a "physical length contraction" to mean that the object ITSELF gets physically shorter. This is manifestly not so in SR". Ken Seto > > 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??? > > ______________________ > Its physical. Any and every physical measurement will show the length has > changed. > > 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. > > ________________________ > Length contraction is physical. What you have written is meaningless, > because you do not describe the frame of reference in which the doors are > open "simultaneously". > > 3. There seem to be contradictory claims amoung the SRians. > > _________________________ > No. People are trying to describe what happens in different ways. These > claims are not "contradictory", they are just different ways of explaining > the same physical phenomenum. > > 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. > > ____________________________ > I'm not sure that what you say is "Tom's premise" actually is his premise.. > Irrespective of that, what you write is wrong; the contraction is actual and > not just an artefact of the measuring technology. > > Ken Seto- Hide quoted text - > > - Show quoted text -
From: kenseto on 1 Feb 2010 21:11 On Feb 1, 8:04 pm, PD <thedraperfam...(a)gmail.com> wrote: > 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. I suggest that you go argue with your SR brother Tom Roberts. He said: "Generally, they would consider a "physical length contraction" to mean that the object ITSELF gets physically shorter. This is manifestly not so in SR." See that? He said that in SR the object ITSELF does not get physically shorter and you contradicted him by insisting that the object does get physically shorter.....btw no compression is inferred in this discussion. Ken Seto > > > 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- Hide quoted text - > > - Show quoted text -- Hide quoted text - > > - Show quoted text -
From: PD on 1 Feb 2010 21:15 On Feb 1, 7:50 pm, kenseto <kens...(a)erinet.com> wrote: > On Feb 1, 6:42 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > > > Juan R. González-Álvarez 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: > > > [... 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. > > The general public know what physical length means. Actually, Ken, what the general public knows about length is rough and imprecise. If you are relying on what you understand from the perspective of your general public grip on it, it's no wonder this is confusing. First you have to learn what length MEANS in physics. >....the length of a > ruler is physical. If you don't like the word physical how about > "material" length contraction? Let's refine this some more. Do you mean by contraction something that happens as a result of a change of configuration of the material, due to a physical interaction such as a squeeze or exchange of heat? Or do you mean by contraction ANY generic change in the difference in positions of the endpoints? There is a difference. > In any case you stated above that > material length contraction does not occur in SR and I agree with that > fully. So I don't know why you accused me of repeatly failed to > understand!!!!!! > > BTW your SR brothers PD and other disagree with you. They insisted > that a moving meter stick itself gets physically (materially) > shorter. Careful! > > Ken Seto > > > > > 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: artful on 1 Feb 2010 21:16
On Feb 2, 12:50 pm, kenseto <kens...(a)erinet.com> wrote: > On Feb 1, 6:42 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > > > Juan R. González-Álvarez 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: > > > [... 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. > > The general public know what physical length means.....the length of a > ruler is physical. Define 'physical' General vague usage isn't the same as the more precise definitions of words requried by science > If you don't like the word physical how about > "material" length contraction? Define 'material' > In any case you stated above that > material length contraction does not occur in SR If you mean a change in the intrinsic properties of objects in their own frames, then of coruse it doesn't > and I agree with that > fully. So I don't know why you accused me of repeatly failed to > understand!!!!!! Because you don't > BTW your SR brothers PD and other disagree with you. No.. they don't > They insisted > that a moving meter stick itself gets physically (materially) > shorter. There is no disagreement .. other than in your imagination. The rest of us aren't confused as you appear to be. |