Is Length Contraction in SR physical??
in [Relativity]
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From: Ste on 7 Feb 2010 04:31 On 7 Feb, 07:08, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> _________________________________ > >> Lots of ways. Normally I measure length by puting a ruler next to an > >> object. > > > And by looking at the readings with your eyes no doubt - so we've gone > > back to a measurement mediated by light? > > No, I feel the edges with my fingers. Blind people can still measure things. Ain't that the truth about physicists! But seriously, yes you can feel, but the fact remains that no "feeling" experiment has ever been done.
From: Ste on 7 Feb 2010 04:34 On 7 Feb, 07:29, mpalenik <markpale...(a)gmail.com> wrote: > On Feb 7, 2:24 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > On 7 Feb, 04:14, mpalenik <markpale...(a)gmail.com> wrote: > > > > On Feb 6, 9:35 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > You can only measure along the x axis at a given t the parts of the > > > > > ladder that intersect the x axis at that given t. > > > > > Of course. Because t=0 represents what you're visually observing in > > > > the present. > > > > Right, so if you see a length contraction in my picture, it means that > > > you're trying to observe parts of the rod that aren't at t=0. Look at > > > the intersection with the volume the rod sweeps out with t=0. This > > > intersection is *larger* than the length of the rod (you can see it > > > extends slightly past the edge of the circle). > > > Ah, I know what you mean. You mean if the rod sweeps out in the > > direction of the t'-axis. Yes, in that case it does become longer - I > > was sweeping it out along the t-axis. > > The rod has to sweep out over the t' axis because it's moving > horizontally. If you sweep it out over the t axis, that represents > something that is at rest (in the x,t frame). Do we agree on this so > far? Yes I'm happy to accept this. > Can we also agree that we have not talked about light, optics, or > propagation delays at all in creating this picture. You could > physically touch the rod at all of the points along the x axis at > t=0. That is, if you had men standing there with there fingers > stretched out at any of those points, the rod would brush up against > them, and thus this has nothing to do with optical illusion. Do we > agree so far? No I don't necessarily agree on this part, because it is neither experimentally proven, and nor is there a physical explanation for it. While I retain an open mind in respect of a physical explanation, I am not willing to accept that there is currently a shred of evidence for it.
From: Ste on 7 Feb 2010 04:37 On 7 Feb, 08:44, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > No it hasn't Paul. The experiment you describe, or anything like it, > has not been carried out, and the literature makes this clear that > physical length contraction has not been observed experimentally. > > _________________________________ > > I already gave you a direct link to where the effect is observed > experimentally hundreds of times a day: > > http://www2.slac.stanford.edu/vvc/theory/relativity.html I'm afraid I do not see any link to research on that site.
From: mpalenik on 7 Feb 2010 04:39 On Feb 7, 4:34 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 7 Feb, 07:29, mpalenik <markpale...(a)gmail.com> wrote: > > > > > > > On Feb 7, 2:24 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 7 Feb, 04:14, mpalenik <markpale...(a)gmail.com> wrote: > > > > > On Feb 6, 9:35 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > You can only measure along the x axis at a given t the parts of the > > > > > > ladder that intersect the x axis at that given t. > > > > > > Of course. Because t=0 represents what you're visually observing in > > > > > the present. > > > > > Right, so if you see a length contraction in my picture, it means that > > > > you're trying to observe parts of the rod that aren't at t=0. Look at > > > > the intersection with the volume the rod sweeps out with t=0. This > > > > intersection is *larger* than the length of the rod (you can see it > > > > extends slightly past the edge of the circle). > > > > Ah, I know what you mean. You mean if the rod sweeps out in the > > > direction of the t'-axis. Yes, in that case it does become longer - I > > > was sweeping it out along the t-axis. > > > The rod has to sweep out over the t' axis because it's moving > > horizontally. If you sweep it out over the t axis, that represents > > something that is at rest (in the x,t frame). Do we agree on this so > > far? > > Yes I'm happy to accept this. > > > Can we also agree that we have not talked about light, optics, or > > propagation delays at all in creating this picture. You could > > physically touch the rod at all of the points along the x axis at > > t=0. That is, if you had men standing there with there fingers > > stretched out at any of those points, the rod would brush up against > > them, and thus this has nothing to do with optical illusion. Do we > > agree so far? > > No I don't necessarily agree on this part, because it is neither > experimentally proven, and nor is there a physical explanation for it. I didn't say anything about experiments. I said, can we agree that we did not invoke optics, light, or propegation delays to create this picture? Or if you'd rather--pretend that we live in a universe where this is the correct description of what is going on. Can you then admit that in this picture, light, propagation delays, and optics have nothing to do with the differences in length and simultanaity? But as long as we're on the subject, what is the physical explanation for 3 dimensional space? If 3 dimensional space doesn't need a physical explanation, why does 4 dimensional space need one? > While I retain an open mind in respect of a physical explanation, I am > not willing to accept that there is currently a shred of evidence for > it.- Hide quoted text - > We have given you plenty of experimental evidence, it's just that every time somebody makes a post describing experimental evidence, you conveniently skip over it. There was a post a few pages back (I think in this thread) where somebody linked to a page on the John Baez physics FAQ that referenced dozens of papers describing experimental evidence.
From: kenseto on 7 Feb 2010 08:20
On Feb 4, 8:12 pm, 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 Hey idiot read what I said. Ken Seto |