Is Length Contraction in SR physical??
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From: kenseto on 5 Feb 2010 09:39 On Feb 4, 9:48 pm, "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 problem is that you also claim that the pole cannot be inside the barn completely with both doors close simultaneously.
From: Peter Webb on 5 Feb 2010 09:39 Then what part of SR requires that the effect be real instead of merely observed? Isn't it more plausible to say that the *observed* position of the ladder, doors, etc, are "rotated in time", but that what is observed does not reflect physical reality? ______________________________ You don't seem to get it. The equations of SR are correct, do you agree with that? For example, do you agree that particle accelerators built using SR correctly function? Well, that's all that physics aims to do, correctly predict the outcome of every experiment. Its up to you how you visualise the fact that time and space are interwoven. One way which is helpful for people with some mathematics background and who have spent more than a month studying physics was suggested by Minkowski. He pointed out that the transforms between time and space were mathematically identical to a rotation in 4D space with one imaginary axis, and that this vector magnitude is a conserved quantity. How "physical" this vector and its rotation actually are depends on your definition of physical. Indeed, whether you want to interpret SR in this way is entirely up to you. Einstein didn't use this in creating SR.
From: Peter Webb on 5 Feb 2010 09:41 >> >> ____________________________________________ >> Perhaps if you defined what you mean by "physical sense" this statement >> would have some meaning. > > Speaking of "physical", I'm starting to wonder whether I've actually > died and gone to hell for my sins, where the Devil has decided that I > am to be tormented by having to explain the meaning of "physical" for > all eternity. Just define it once. The only argument you seem to have is that it isn't "physical", and you won't say what that means. So you have no argument at all, and are just a troll.
From: kenseto on 5 Feb 2010 09:52 On Feb 4, 10:19 pm, mpalenik <markpale...(a)gmail.com> wrote: > On Feb 4, 10:12 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 5 Feb, 00:27, artful <artful...(a)hotmail.com> wrote: > > > > That you cannot see the analgoy just shows you have NO idea what SR > > > says > > > > Both have a longer length object fitting within a shorter spae > > > > Both have a geometrical rotation and projection > > > > The ladder fits thru the doorway just as 'physically' as a pole fits > > > in the barn. > > > How on Earth do you work that one out? > > > For the analogy to work, the ladder must be constrained lengthwise, > > not widthwise.- Hide quoted text - > > > - Show quoted text - > > This is what we've been trying to get across to you. It has to do > with coordinates and what one observer calls time and space relative > to another. > > The ladder is a little bit too long to fit into the barn but you could > rotate it and still fit it into the barn. Say, for example, you lift > the front end so the ladder is now at a 45 degree angle. You could > now fit it into the barn. You've rotated part of it into "height", > from "length". So you now agree that length contraction in SR is not physical....Right? It is merely a geometric projection effect....right? Ken seto So > > But there's another way you could rotate it, as well. You can rotate > it into "time". If you run with the ladder, you're "rotating" the > front of it a little bit into the future and the back of it a little > bit into the past. > > What a moving observer percieves as "time" is the direction of his > motion through 4 dimensional spacetime. What he percieves as "space" > is the 3 dimensional volume perpendicular to that direction. Thus, > "space" in the moving frame is not the same as "space" in the rest > frame. It extends part way into the future along one direction and > part way into the past along the other (in the rest frame).- Hide quoted text - > > - Show quoted text -
From: kenseto on 5 Feb 2010 10:15
On Feb 5, 12:23 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > kenseto wrote: > > Fitting a ladder through a narrow door way is not the same as fitting > > a long pole into a shorter barn with both doors close simultaneously. > > No. But the situations are ISOMORPHIC in SR. Both are examples of geometric > projection. Geometris projection can explain the barn and the pole paradox. But most of your SR brothers insist that length contraction is physically real. IOW they think that a ladder can fit through a narrow door way because it is physically contracted. Ken Seto > > Tom Roberts |