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From: Inertial on 11 May 2010 19:21 "harald" <hvan(a)swissonline.ch> wrote in message news:add3966f-1ea3-43a2-8f5b-b96932a57393(a)q30g2000yqd.googlegroups.com... > On May 11, 2:01 pm, "Inertial" <relativ...(a)rest.com> wrote: >> "harald" <h...(a)swissonline.ch> wrote in message >> >> news:681a3280-dc36-4fff-858d-3c44e8e03edf(a)n15g2000yqf.googlegroups.com... >> >> >> >> > On May 11, 1:55 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: >> >> Da Do Ron Ron wrote: >> >> >> > [from a Roberts prior post] >> >> >> It boggles the mind to think you don't accept that two legs have >> >> >> identical lengths if when you hold them up next to each other their >> >> >> ends line up [or when a ruler measures them as equal]. >> >> >> > Let's try to attain some common ground by using the math: >> >> >> OK. But please remember I am using the context of SR, not some >> >> unspecified and >> >> nebulous "aether" theory. And I am using SR as known in 2010, not as >> >> discussed >> >> in 1905-20 (the meanings of some important words have changed since >> >> then). >> >> > Very good - you are making progress! >> > As you now admit yourself, SRT has been reformulated almost beyond >> > recognition (to avoid confusion, shouldn't we call that "Minkowski >> > Spacetime Physics"?). >> >> He didn't say that .. do you commonly read things into > posts that >> people don't say? > > Hi Inertial you wrongly read a citation in my words. Nope > Tom rightly > remarked here above that "the meanings of some important words have > changed since 1905-1920" I know what he said .. that is NOT saying that "SRT has been reformulated beyond recognition" > - to the extent that (as Tom also noted here > above), while for example according to original SRT, "moving lengths > shorten", according to Minkowski Spacetime Physics "lengths cannot > change". Both say the same things. spatial/measured lengths *do* shorten in both 'physics', proper/invariant lengths do *not* shorten in both 'physics'. The difference is what length is implied by just using the unadorned term 'length'. > Tom calls the original expression an "older meanings of > words". One doesn't use 'length' for the invariant length .. on uses 'invariant length' or 'proper length' or 'interval'. Of course, in some cases, where the context is implied (eg in an article talking about invariant lengths) one may omit the adjective :) Length is still length (the spatial separation of two events at a given time) Regardless, a refinement in the terms used in modern physics does not mean a reformulation. >> > But note that at least until 1932 (KTX), SRT was formulated and >> > compared with other theories and hypotheses in the way that DDRR does. >> > Certain concepts that those definitions relate to are difficult to >> > understand in your language. Are you capable of a discussion with DDRR >> > using the common definitions of words of SRT in the period 1905-1932? >> >> What or who is DDRR ?? > > The OP, with whom Tom is debating based on mutual > misunderstanding. :-)) I don't think I've had the (mis?)fortune of discussing with him/mer >> > Coincidentally my main physics textbooks of around 1980 (alonso & >> > Finnn) was mostly compatible with those definitions; that turned out >> > to be very helpful for understanding old papers. > > Harald
From: Inertial on 11 May 2010 19:23 "Da Do Ron Ron" <ron_aikas(a)hotmail.com> wrote in message news:167e49e8-d4af-4d4c-9aad-d7b617ed4b2c(a)h11g2000vbo.googlegroups.com... > 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. As Wheeler correctly noted, the > intrinsic length > of a rod is its absolute length which can vary with rod motion through > space. No .. it doesn't. > (However, note that Wheeler improperly placed quotes around "motion > through absolute space" - 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. > > Proper length, on the other hand, is that which is measured by an at- > rest ruler, Nope .. though a mutually at-rest ruler will come up with measured length the same as proper length > and this may or may not be the actual or absolute length > depending upon whether > the rod is currently at absolute rest or not. (This is simply because > a ruler > will absolutely shrink with the rod, thereby giving a false reading.) There is no absolute rest > If you keep on making such grievous errors, then this thread may never > end. You are the one confused and in error >> "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) Read a real physics book
From: Inertial on 11 May 2010 19:37 "Tom Roberts" <tjrob137(a)sbcglobal.net> wrote in message news:aaWdnfp_3a4aSHTWRVn_vwA(a)giganews.com... > Inertial wrote: >> [... statements I basically agree with ...] >> Spacetime itself takes on the characteristics of an aether without >> actually being a 'substance'. > > No. I don't think you are actually disagreeing with me .. perhaps misunderstanding what I said. > What actually happens in SR/GR is that the geometry makes an aether > superfluous -- Yeup .. I was not saying otherwise. That is what I was saying .. that spacetime (its geometry) results in the same properties that we observe .. without there being an aether 'substance' required. Eg the speed of light is (by some) regarded as what the wave propagation speed of the aether must be .. but it is equal explained by the geometric properties of spacetime >if there were one it would be required to do absolutely nothing. Assuming spacetime is as per SR/GR. If it was a simple newtonian/galillean/euclidean space and time (as LET assumes it is), then the aether needs to 'do' something. > IOW: the relevant "physical relationships" in LET are geometrical > relationships in SR/GR. Yeup ... that's just what I was saying > For instance, the "physical contraction" of moving rods and the > "physical slowing" of moving clocks in LET become merely two > aspects of geometrical projection in SR/GR. As far as what we measure .. yes. The metaphysics and 'hidden reality' behind what LET says happens is different to what SR says .. the results on reality as it appears to us and as it affects us is the same. Although not when one starts to consider fields and forces other than the EM that the aether is supposed to host. > Remember the difference between world and model: spacetime is part of the > model, while aether is putatively part of the world. Spacetime cannot > "take on characteristics of an aether", because they are components of > completely different realms. A pedantic difference. Characteristic are what we measure. The geometry of the world means that we measure characteristics/properties. > Spacetime cannot be considered to be the model of some aether, Never said it was > as it is just a manifold with metric (an associated geometry) -- it has no > physical aspects with which to model a physical substance like aether. Never said it did .. but that the world is as modeled by SR/GR means we get things like light propagation speed being c as a result of that geometry .. so need for it being the wave propagation speed of some medium. > The thing most aether advocates fail to see is that they have > IMPLICITLY selected a geometry, Euclidean 3-space. And they have > done so because of personal biases. Exactly .. they demand justification of Minkowski geometry .. that there must be 'something' that causes the world to have that geometry, while they tacitly assume Euclidean geometry and don't see the hypocrisy there. > So they must postulate the > geometry PLUS the existence of an aether with a specific set of > complex properties that are highly non-obvious. SR, on > the other hand, needs only to postulate its Minkowski geometry. Yeup .. KISS and a close shave by Occam needed > That is the same level as aether advocates selecting Euclidean > 3-space, and completely avoids having to assume the complex > properties of aether. Moreover, the aether advocates have not > begun to address the subtle and complex issues related to the > quantum aspects of light and electrodynamics, and there is grave > doubt that any aether approach can handle that (with the > potential exception of Ilja's theory, which has other problems). Nicely put. As suspected, we are both saying the same things (I just tried to do it in a single sentence in simplified language :))
From: Surfer on 12 May 2010 01:37 On Mon, 10 May 2010 13:40:48 -0700 (PDT), "Dono." <sa_ge(a)comcast.net> wrote: >On May 10, 12:13 pm, Surfer <n...(a)spam.net> wrote: >> On Sun, 9 May 2010 10:18:30 -0700 (PDT), "Dono." <sa...(a)comcast.net> >> wrote: >> >> The interference fringes observed by Shamir and Fox could have been >> formed by reflection of light from the ends of the perspex rods. >> > >Keep trying , Peter > Well, unlike Demjanov, Shamir and Fox don't mention taking any steps to avoid that happening. cf Shamir and Fox, N. Cim. 62B no. 2 (1969), pg 258. versus V.V. Demjanov http://arxiv.org/abs/1003.2899
From: Dono. on 12 May 2010 01:52
On May 11, 10:37 pm, Surfer <n...(a)spam.net> wrote: > > Well, unlike Demjanov, Shamir and Fox don't mention taking any steps > to avoid that happening. > Shamir and Fox, as well as Trimmer are scientists, Demjanov is just another pathetic ignorant that knows nothing about elementary SR. Keep trying , Peter. |