Is Length Contraction in SR physical??
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From: BURT on 7 Feb 2010 22:05 On Feb 7, 6:59 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 7 Feb, 09:39, mpalenik <markpale...(a)gmail.com> wrote: > > > > > > > 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? > > I'm willing to go with this assumption for the purposes of letting you > make an argument, but I'm quite sceptical that this "touching" is > achievable in practice without the mediation of EMR. > > > 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? > > You should note my scepticism once you start saying "let's pretend SR > is not about light", but as I say I will of course hear your argument > out. > > > 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? > > 3 dimensional geometry does need a physical explanation, and it's very > easy to provide one that appeals to our most obvious intuitions. > > It's also easy to consider "time" as an additional mathematical > "dimension", but which has a completely different conceptual basis in > the physical world. That is, the philosophy of time is a question for > the ages, but it embodies an intuitive aspect of the physical world > which is 'change'. > > > > 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. > > > 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. > > I haven't skipped over experimental evidence at all. There's no point > just vaguely alluding to unspecified experimental evidence, which I am > neither familiar with, nor have access to, and which you do not > discuss in the context of my arguments. Indeed, the FAQ to which you > refer quotes "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". It then goes on to point > out that there has been an indirect proof of length contraction... > mediated by EMR! > > Certainly, if *you're* familiar with all this experimental evidence, > then surely you can either point out where the evidence (not theory) > contradicts my hypothesis, or on the other hand concede that the > evidence would not discern between existing interpretations and mine.- Hide quoted text - > > - Show quoted text - Round atoms can't go flat. There is no flat physics. Mitch Raemsch
From: mpalenik on 7 Feb 2010 22:16 On Feb 7, 9:59 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > 3 dimensional geometry does need a physical explanation, and it's very > easy to provide one that appeals to our most obvious intuitions. I just wanted to say "it appeals to our most obvious intuitions" is not a physical reason. Part of your problem is that you do treat that as if it's a physical reason. Obvious intuitions can be wrong--such as Aristotle's obvious intuition that objects need a force acting on them to keep them in motion, which was the prevailing thought in physics for over 1000 years.
From: Ste on 7 Feb 2010 22:21 On 7 Feb, 16:31, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: > > This is precisely what allows us to qualify you as a troll. You are > here, without any formal education in physics or mathematics, to > discuss your *views* and nothing more. And? Are you suggesting that no one can possibly comment or even understand the physical world unless they have a formal education to degree level or beyond? > You have not considered that > your *views* may be partially or completely wrong and you are not > willing to accept that situation and also not willing to accept our > help to change your status of ignorance to other of at least a better > understanding of what science is. I am perfectly willing to consider my views are wrong, but *not* on the basis that someone simply *says* that I'm wrong, without any apparent willingness or ability to identify the mistake. > Nothing in physics has anything to do with ideology. If that were the > case, Einstein and others in his time would have clearly being > dismissed as wackos. Instead most of them received well deserved Nobel > prizes. Einstein was eventually dismissed by his colleagues as ideological. But that aside, why on Earth would you think that people who have an ideology would necessarily be dismissed as "wackos"? Milton Friedman won the Nobel, and his works were nothing but a "scientific" distillation of capitalist ideology, while most of the assumptions underpinning neoclassical economics have been totally and repeatedly falsified by the evidence. Indeed, free markets and monetarism have brought at least as much death and misery to the countries where they were imposed, as to the counties where "communism" was imposed. Indeed, I think you should stop here Miguel, before you make a fool of yourself. > Modern physics is not an easy subject. I took my first course in > modern physics over 40 years ago and I'm still learning and, most > probably, will need several more years to even feel comfortable to > discuss some of the subjects at the level they are discussed in this > forum (which is rather basic). You still have a very long road to > cover. > > Up to now you are just spouting nonsense. "If at first a theory is not absurd..."
From: Peter Webb on 7 Feb 2010 22:41 Certainly, if *you're* familiar with all this experimental evidence, then surely you can either point out where the evidence (not theory) contradicts my hypothesis, or on the other hand concede that the evidence would not discern between existing interpretations and mine. ____________________________________ I have now posted exactly what you are asking for three times. Here it is a fourth time: http://www2.slac.stanford.edu/vvc/theory/relativity.html It clearly states what would be observed in SLAC if length contraction of the track did not occur, states the impact of relativistic shortening of the track, and then states that the experimental results are exactly as are predicted using SR's length contraction, and are not as predicted if length contraction did not occur. Why do you keep complaining that there is no experimental support for length contraction, when I have given you an extremely reputable site which provides exactly that? BTW, the same is true of any particle accelerator built in the last 50 years. People who doubt SR seem to forget that we routinely accelerate particles close to the speed of light in countless particle accelerators world-wide every day, and precisely measure resulting speeds, energies and momenta. These accelerators simply would not work if SR was wrong.
From: YBM on 7 Feb 2010 22:54
Ste a �crit : > On 7 Feb, 16:31, "papar...(a)gmail.com" <papar...(a)gmail.com> wrote: >> This is precisely what allows us to qualify you as a troll. You are >> here, without any formal education in physics or mathematics, to >> discuss your *views* and nothing more. > > And? Are you suggesting that no one can possibly comment or even > understand the physical world unless they have a formal education to > degree level or beyond? It has not to be formal. You could get it by your own. Unfortunaly you probably won't. |