Is Length Contraction in SR physical??
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From: Ste on 5 Feb 2010 21:14 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.
From: Ste on 5 Feb 2010 21:16 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!
From: mpalenik on 5 Feb 2010 21:36 On Feb 5, 9:04 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 5 Feb, 15:55, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Feb 4, 8:34 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > 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!". > > > Your conclusion "no" is in conflict with experimental measurement. > > When intuition conflicts with experimental measurement, then it is > > intuition that must give way. > > I checked Paul before I gave this answer. Length contraction has never > been experimentally tested. So my intuition does *not* conflict with > experimental evidence.- Hide quoted text - > > - Show quoted text - Length contraction must follow for logical consitancy based on other measurements. If the speed of light is constant in every reference frame, length contraction must necesessarily follow, as we've described it to you. That's how the original derivation of all of special relativity worked. You apply logic to the two postulates of relativity and see what it necessitates for consistancy. If the speed of light is constant, E=mc^2 logically follows (or rather, E^2 = p^2c^2 + m^2c^4), as does length contraction, time dilation, and the differences is simultanaity. Can you admit this is the case? So while length contraction may not have been experimentally measured directly, what has been measured? The consistancy of the speed of light in every frame Time dilation (in multiple different ways) The relativstic energy/momentum relationship (repeatedly, in multiple different ways) Gravitational lensing (which matches the predictions of GR, which requires that the predictions of special relativity hold in each local Lorentz frame) The dopplar shift of predicted by relativity (which is slightly different than the non-relativistic dopplar shift that you get for something like sound waves, for example). Ste, could you try doing the exercise that I posted in reply to Ken's message?
From: mpalenik on 5 Feb 2010 21:36 On Feb 5, 9:16 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!- Hide quoted text - > > - Show quoted text - Just because you don't like the answers doesn't mean he's not being answered.
From: mpalenik on 5 Feb 2010 21:45
On Feb 5, 9:40 pm, Ste <ste_ro...(a)hotmail.com> wrote: > Then perhaps that is why science doesn't get as much interest these > days, Doesn't get as much interest from who? what are you talking about? There's plenty of interest in science, plenty of students in physics classes, and plenty of people getting degrees in physics. |