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From: whoever on 13 May 2010 18:53 "Da Do Ron Ron" <ron_aikas(a)hotmail.com> wrote in message news:c5bc5ddf-b07c-47f6-b7fa-b84893832cf3(a)k29g2000yqh.googlegroups.com... > On May 13, "whoever" whatever or Inertial wrote: >> "Da Do Ron Ron" wrote in >> messagenews:e1830739-517f-484d-84d7-6e5df36e4c92(a)h9g2000yqm.googlegroups.com... > >> The speed of light is the same in all frames. > > Cite the experiment whereby light's speed between two clocks was > measured. (no transported or rotating clocks because they can run > slow) Why do you think you even need to do that? >>> But Einstein was drastically wrong in claiming that we have no >>> means of detecting this absolute motion > >> No .. he wasn't > > Show how light's speed between two clocks will be c in more than > one inertial frame. (use only one light source to make sure that > you have two different frames - otherwise, you will just be > repeating a single-frame experiment) Study SR (or even LET) and you'll know how. Was the above supposed to be some argument against my claim that Einstein wasn't wrong? > [T Robts claimed] >>>>>> "length of an arm measured in frame S" means a measurement >>>>>> in frame S, and if S is moving relative to the arm then the >>>>>> value can be different from the proper length of the arm. > > [~RA~ merely enquired] >>>>> Why different? >>>>> (full details please) > > ["Inertial" replied] >>>> Read a real physics book > > [~RA~] >>> For many who are reading this cute little thread, this quickie reply >>> perfectly masks the import of the quickie question, so "Inertial" >>> did his job properly (which was to evade the issue). > > ["Inertial" aka "whoever"] >> I didn't evade anything > > You are still evading because you did not answer the question. > I firmly predict that you will never answer it. I told you if you want the answer .. go read a physics text that explains it. That's not evading the question. I'm not here to be quizzed by a crackpot like you who has shown he doesn't understand physics to start with and so is in no position to 'test' me. --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: Tom Roberts on 13 May 2010 23:09 Da Do Ron Ron wrote: > On May 10, 7:55 pm, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: >> "length of an arm" can only mean the INTRINSIC length of the arm; >> its proper length. > > Da Do Ron Ron writes: > Speaking of being confused, proper length and the intrinsic length are > two entirely different things. Not in SR. Nor in any modern theory of physics. The intrinsic length of an object means the length that the object itself inherently has, without relation to anything else. That can only mean the length measured by a ruler held directly up to the object without slipping -- i.e. its proper length. I repeat: this does not change if you think that objects do "shrink" due to their "absolute motion" -- the ruler and object will necessarily be affected the same, and the value obtained will still be correct. > As Wheeler correctly noted, the > intrinsic length > of a rod is its absolute length which can vary with rod motion through > space. That clearly requires "absolute length" to be meaningful, and in SR it is not. I suspect you are misquoting Wheeler. > (However, note that Wheeler improperly placed quotes around "motion > through absolute space" HA!!! -- you did misquote him. He used quotes to indicate the phrase is of questionable meaning. That is not "improper". And you probably omitted his context as well.... >- Einstein neither denied or proved that > absolute motion does not exist, but only postulated that we cannot > detect such motion.) Intrinsic > length is the real, absolute, or true length. But if it is unknowable it is useless, and has no place in physics. Physics is the process of MODELING natural phenomena and systematically refining those models via experiment and observation. Unknowable quantities such as "absolute motion" cannot participate in such models. > Proper length, on the other hand, is that which is measured by an at- > rest ruler, No, if by "at rest" you mean "absolutely at rest" (where my quotes imply the phrase is of questionable meaning). Proper length is the length measured by a ruler that is comoving with the object being measured. There is no implication of "at rest" here, except "at rest relative to the object being measured". You REPEATEDLY assume some sort of "absolute motion", without realizing you are doing so, and without being able to define what "absolute motion" means. >> "length of an arm measured in frame S" means a measurement in frame S, >> and if S is moving relative to the arm then the value can be different >> from the proper length of the arm. > > Why different? > (full details please) Because in SR a frame moving relative to the object will PROJECT the object's length differently onto the moving frame than onto the object's rest frame, and thus the value obtained for the PROJECTION will be different from its proper length. In SR, the length of an object measured in a given frame is always the proper length of the object PROJECTED onto the measurement frame. As I have said so often: when you attempt to carry a ladder through a narrow doorway, what determines whether it will fit is the projection of the ladder's length onto the doorframe. Clearly rotating the ladder changes that projection, and can make it fit or not fit. In SR, relative motion is a similar sort of rotation, with the doorway replaced by measurements of length for rulers and time intervals for clocks -- those are PROJECTIONS of the proper length or proper time onto the measurement frame. At base your problem seems to be that you do not actually know and understand any theory of physics. You just grope for various phrases and words that you THINK have the meaning you want them to have, but without an underlying theory they don't have well-defined meanings at all. This includes such phrases as "absolute motion", "absolute rest", "intrinsic length" (your meaning, not mine). This lack of well-defined phrases makes it impossible for you to either write or THINK accurately enough for the subject to make sense. Physics is more subtle than you think, and indeed even more subtle than it is possible for you to think using such poorly- defined phrases. Tom Roberts
From: Tom Roberts on 13 May 2010 23:28 Paul Stowe wrote: > I thought physics was about 'the world, universe, & > everything'... That's your basic problem -- you don't understand what science really is. You are human, and can never know ANYTHING about the world. All you can do is make (mental) models of the world and understand them. You have done so since birth, and do it without even realizing it -- every word or thought about some aspect of the world is really related to a MODEL of that aspect. But the model you constructed in the cradle is WRONG [#], and it takes a great effort to understand how and why, and what it takes to fix it. Until you actually make that effort you will remain confused. [#] I.e. does not accurately model the world we inhabit. In particular, it is only accurate in your everyday life, where it was developed; it is useless in regimes far removed from your experiences, where relativity and quantum theories are required. Modern physics arose because unlike yourself, physicists have made efforts to make such phenomena part of their experiences, and part of their models. Tom Roberts
From: Tom Roberts on 14 May 2010 11:00 harald wrote: > On May 12, 1:21 am, "Inertial" <relativ...(a)rest.com> wrote: >> One doesn't use 'length' for the invariant length .. on uses 'invariant >> length' or 'proper length' or 'interval'. > > Tom does. No, Tom most definitely does not, as a perusal of my writings around here will show. WHAT I SAID is that "length of an object" can only mean its intrinsic length, as no other quantity/qualifier is mentioned. Look at the CONTEXT of what I wrote -- I was pointing out ambiguities in OTHER PEOPLE'S words. I never speak so loosely, or at least make serious efforts to avoid doing so. You need to learn how to read more accurately. Context matters, as do the actual words themselves. Tom Roberts
From: bz on 14 May 2010 11:54
Da Do Ron Ron <ron_aikas(a)hotmail.com> wrote in news:e1830739-517f-484d- 84d7-6e5df36e4c92(a)h9g2000yqm.googlegroups.com: > But Einstein was drastically wrong in claiming that we have no means > of detecting this absolute motion because he overlooked the extremely > simple fact that light itself is an absolute frame. (It's speed in or > through space is fixed - no slowing - no speeding up - and it is a > known speed - so this means that any light ray in space is certainly > an absolute frame.) > YOUR 'absolute frame' is 'absolutely useless' for relating objects in motion to each other, based on their motion with respect to your 'absolute frame'. For an absolute frame to be useful, observers moving at different velocities should be able to compute their relative velocities wrt each other from their velocity wrt the absolute frame. For example, I measure my velocity wrt point A and know your velocity wrt the same point (you sent me your measurement). I can compute our relative velocities because 'point A' is 'absolutely the same point' for both of us. This is true EVEN IF point A is in motion, just as long as we make our measurements at the same time. However, it should be noted that 'A' is NOT an 'absolute frame', it is a single point that we have agreed upon and we could just as well use an infinite number of other points. Ah, but there is a problem with the real universe. Since there is no absolute frame, we can't 'make our measurement at the same time' unless we are in the same place at the moment the measurement is made OR we have synchronized our clocks. Knowing that light moves at 'c' does NOT help us measure our relative velocity (unless we know the exact wavelength of the light at the time of emission) because we will measure the velocity of the light as 'c' no matter what our relative velocities are wrt each other. However there are forms of 'absolute motion' in our universe. One such form is 'rotation'. An object with mass (of non zero radius) is either in rotation or is isn't. We can tell, even in a sealed room, if it is rotating or not. -- bz please pardon my infinite ignorance, the set-of-things-I-do-not-know is an infinite set. |