An apology to Androcles
in [Relativity]
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From: Uncle Ben on 31 Jul 2010 12:02 On Jul 31, 10:50 am, blackhead <larryhar...(a)softhome.net> wrote: > On 31 July, 03:49, Uncle Ben <b...(a)greenba.com> wrote: > >........... You may be right, but I don't think so. I've spent enough time on Androcles for a while. He is fun to tease, but he is hopeless to teach. If you want to take over, have at him! Hint: He reads the section on length of rods of Einstein 1905, relativity, up to the critical paragraphs (a) and (b) but does not then read (a) and (b). The introductory paragraph introduces a rod to be measured and establishes that its rest length is L. Paragraph (a) then sets the rod in motion with a comoving observer repeating the same measurement, and, by the principles of relativity, getting the same answer (the critical part Andy doesn't read) that results in xi=L. Only then in (b) does E. approach the measurement of the now-moving rod, resulting in the value of x'. (For a long time A. thought that x' was the result of an unmentioned LT, instead of a moving point (x) in K at the far end of the moving rod relative to the moving near end at the origin (vt) of system k, yielding the desired (constant) length x-vt in K of the rod.) Uncle Ben
From: waldofj on 31 Jul 2010 15:42 On Jul 31, 12:02 pm, Uncle Ben <b...(a)greenba.com> wrote: > On Jul 31, 10:50 am, blackhead <larryhar...(a)softhome.net> wrote: > > > On 31 July, 03:49, Uncle Ben <b...(a)greenba.com> wrote: > > >........... > > You may be right, but I don't think so. > > I've spent enough time on Androcles for a while. He is fun to tease, > but he is hopeless to teach. If you want to take over, have at him! > > Hint: He reads the section on length of rods of Einstein 1905, > relativity, up to the critical paragraphs (a) and (b) but does not > then read (a) and (b). > > The introductory paragraph introduces a rod to be measured and > establishes that its rest length is L. > > Paragraph (a) then sets the rod in motion with a comoving observer > repeating the same measurement, and, by the principles of relativity, > getting the same answer (the critical part Andy doesn't read) that > results in xi=L. > > Only then in (b) does E. approach the measurement of the now-moving > rod, resulting in the value of x'. That's not correct. He does assert that the length of the (moving) rod in the stationary system will be different from L but he doesn't actually establish the relationship until section 4. I'm not sure why he even mentions measuring rods at this point in the paper since all he does at this point is discuss the relativity of simultaneity. x' is introduced to refer to an arbitrary point in the moving system (using stationary coordinates) and is later used as the variable of differentiation (I wonder where he got the idea to do that!). It has nothing to do with the measuring rod mentioned previously.
From: Inertial on 31 Jul 2010 18:42 "ben6993" wrote in message news:04c03713-3840-4dd5-b9bd-0a32c3298392(a)w12g2000yqj.googlegroups.com... On Jul 31, 3:49 am, Uncle Ben <b...(a)greenba.com> wrote: > On Jul 30, 9:39 pm, blackhead <larryhar...(a)softhome.net> wrote: > > > > > > > On 31 July, 01:46, Uncle Ben <b...(a)greenba.com> wrote: > > > > On Jul 30, 8:34 pm, mpc755 <mpc...(a)gmail.com> wrote: > > > > > On Jul 30, 3:10 pm, Uncle Ben <b...(a)greenba.com> wrote: > > > > > > An apology to Androcles > > > > > > I had thought that the Einstein Expansion, proclaimed by Androcles > > > > > in > > > > > sci.physics.relativity, was an error of confusing frames of > > > > > reference. But I was wrong. > > > > > > In his 1905 relativity paper, Einstein showed that x' = xi/gamma, > > > > > where x' is the length of a moving rod with respect to a > > > > > stationary > > > > > frame of reference K and xi is the length of the moving rod with > > > > > respect to a frame k comoving with it. My difference with > > > > > Androcles > > > > > was that I claimed that xi is the proper length L of the rod and > > > > > the > > > > > shorter x' is a contracted length L/gamma. > > > > > > I thought that Androcles had these two backward. But no, he has > > > > > persuaded me otherwise; He agrees that x' is shorter than xi, but > > > > > he > > > > > insists that x' is L and xi is an expanded length Lgamma. The > > > > > proper > > > > > length of the rod in k increases because of the existence of > > > > > another > > > > > frame of reference K moving with respect to it. (This other frame > > > > > K is > > > > > called the "stationary" frame in Einstein's paper, but it can be > > > > > considered moving the other way with respect to the rest frame k > > > > > of > > > > > the rod.) > > > > > > This startling fresh idea would never have occurred to me without > > > > > Androcles's guidance. > > > > > > It seems strange that a nearby frame of reference K, by its > > > > > relative > > > > > motion, can expand a rod with respect to the rod's own proper > > > > > frame k, > > > > > while the rod maintains a constant length with respect to K > > > > > itself. > > > > > > Imagine me in a Concorde (k) flying over you on the ground (K) > > > > > sucking > > > > > on my cigar that had length L when I bought it. It seems strange > > > > > that > > > > > to you the cigar has length L, but because I am flying within > > > > > your > > > > > frame of reference, my cigar is Lgamma long. In fact, because of > > > > > your > > > > > frame of reference, the Concord is stretched by gamma for me but > > > > > not > > > > > for you. I have no idea why my cigar is now longer, because I have > > > > > no > > > > > idea that you are down there. > > > > > > It seems odd, doesn't it. Perhaps Androcles will explain it to > > > > > us. > > > > > > Uncle Ben > > > > > In this rare instance of someone abandoning their constant > > > > delusional > > > > denial state of existence, any chance you can take it a step further > > > > and answer the following? > > > > > Will the ripple eventually reach the Earth? If not then why not? > > > > > 'Hubble Finds Ghostly Ring of Dark > > > > Matter'http://www.nasa.gov/mission_pages/hubble/news/dark_matter_ring_featur... > > > > > "Astronomers using NASA�s Hubble Space Telescope got a first-hand > > > > view > > > > of how dark matter behaves during a titanic collision between two > > > > galaxy clusters. The wreck created a ripple of dark matter, which is > > > > somewhat similar to a ripple formed in a pond when a rock hits the > > > > water." > > > > > The ripple will eventually reach the Earth and this is evidence dark > > > > matter exists from the galaxy cluster to the Earth. This is evidence > > > > dark matter is the medium of space in which light waves propagate. > > > > > Pressure exerted towards matter by dark matter displaced by the > > > > matter > > > > is gravity.- Hide quoted text - > > > > > - Show quoted text - > > > > I have no idea, and this thread is abought the Einstein Expansion.- > > > Hide quoted text - > > > > - Show quoted text - > > > Androcles rechristened the space LT as "Einstein's expansion" formula: > > > xi = x'/sqrt(1 - v^2/c^2) with x' = x-vt > > 1905 paper. > > Used correctly, it transforms x coordinates of the same event between > > different frames, not lengths directly. Androcles plugs in lengths for > > xi, x' without considering what's involved in measuring a length. For > > a start, it involves measuring space coordinates at the *same* time > > and subtracting them from one another to get a length, if it's moving > > in that frame. If the end points remain at the same locations for all > > time, then simultaneity doesn't matter.- Hide quoted text - > > > - Show quoted text - > > Some ng history, Blackhead: > > This subject has been discussed often, and in some discussions > Androcles ha progressed all the way to a length comparison, following > Einstein's 1905 paper. I now believe he has got it all right except > for the final step, which is assigning values to x' and xi. He agrees > in the meaning of the variables x' and xi, including correctly that > x' < xi. Where he goes off the track is to insist that x'=L, and > therefore xi= Lgamma. The correct path is to assign xi=L and conclude > that x' = L/gamma. > > The absurdity of this error is the point of this thread. > > Uncle Ben- Hide quoted text - > > - Show quoted text - >I have been led through all this a few months ago, line at a time of >the relevant section of the 1905 paper, by Androcles. Thank you >Androcles. But my memory of the details have faded. You poor thing .. falling for androcles lies >OK, so Androcles is finding that Einstein's beta is 2 for v = 0.866c. >In other words, the length of a rod measured in frame k (using xi and >tau) is twice as big as it would be if measured in frame K (using x >and t). That's fine isn't it? Yeup .. it is measured shorter from the moving frame. >The rod is stationary withinin frame k So k is the rest frame, and the rod is twice the length that it is measured to be in the moving frame K >so its length is easily >measured as L within frame k. (Einstein's paper uses x' instead of L.) >So xi=L gives the rod length in frame k. >Now what is the rod length in frame K? Since xi=2x, then x=0.5L. Ie >we see the moving rod as shorter than it is measured in its rest frame. You just got it backwards .. the same as Ancy .. he can't do simple math and things the x/2 is twice as big as x
From: Inertial on 31 Jul 2010 18:46 "ben6993" wrote in message news:f35de583-2f89-4051-b89d-dd846b364e26(a)u26g2000yqu.googlegroups.com... On Jul 31, 2:15 pm, Uncle Ben <b...(a)greenba.com> wrote: > On Jul 31, 8:36 am, ben6993 <ben6...(a)hotmail.com> wrote: > > > > > > > On Jul 31, 3:49 am, Uncle Ben <b...(a)greenba.com> wrote: > > > > On Jul 30, 9:39 pm, blackhead <larryhar...(a)softhome.net> wrote: > > > > > On 31 July, 01:46, Uncle Ben <b...(a)greenba.com> wrote: > > > > > > On Jul 30, 8:34 pm, mpc755 <mpc...(a)gmail.com> wrote: > > > > > > > On Jul 30, 3:10 pm, Uncle Ben <b...(a)greenba.com> wrote: > > > > > > > > An apology to Androcles > > > > > > > > I had thought that the Einstein Expansion, proclaimed by > > > > > > > Androcles in > > > > > > > sci.physics.relativity, was an error of confusing frames of > > > > > > > reference. But I was wrong. > > > > > > > > In his 1905 relativity paper, Einstein showed that x' = > > > > > > > xi/gamma, > > > > > > > where x' is the length of a moving rod with respect to a > > > > > > > stationary > > > > > > > frame of reference K and xi is the length of the moving rod > > > > > > > with > > > > > > > respect to a frame k comoving with it. My difference with > > > > > > > Androcles > > > > > > > was that I claimed that xi is the proper length L of the rod > > > > > > > and the > > > > > > > shorter x' is a contracted length L/gamma. > > > > > > > > I thought that Androcles had these two backward. But no, he > > > > > > > has > > > > > > > persuaded me otherwise; He agrees that x' is shorter than xi, > > > > > > > but he > > > > > > > insists that x' is L and xi is an expanded length Lgamma. The > > > > > > > proper > > > > > > > length of the rod in k increases because of the existence of > > > > > > > another > > > > > > > frame of reference K moving with respect to it. (This other > > > > > > > frame K is > > > > > > > called the "stationary" frame in Einstein's paper, but it can > > > > > > > be > > > > > > > considered moving the other way with respect to the rest frame > > > > > > > k of > > > > > > > the rod.) > > > > > > > > This startling fresh idea would never have occurred to me > > > > > > > without > > > > > > > Androcles's guidance. > > > > > > > > It seems strange that a nearby frame of reference K, by its > > > > > > > relative > > > > > > > motion, can expand a rod with respect to the rod's own proper > > > > > > > frame k, > > > > > > > while the rod maintains a constant length with respect to K > > > > > > > itself. > > > > > > > > Imagine me in a Concorde (k) flying over you on the ground (K) > > > > > > > sucking > > > > > > > on my cigar that had length L when I bought it. It seems > > > > > > > strange that > > > > > > > to you the cigar has length L, but because I am flying within > > > > > > > your > > > > > > > frame of reference, my cigar is Lgamma long. In fact, because > > > > > > > of your > > > > > > > frame of reference, the Concord is stretched by gamma for me > > > > > > > but not > > > > > > > for you. I have no idea why my cigar is now longer, because I > > > > > > > have no > > > > > > > idea that you are down there. > > > > > > > > It seems odd, doesn't it. Perhaps Androcles will explain it > > > > > > > to us. > > > > > > > > Uncle Ben > > > > > > > In this rare instance of someone abandoning their constant > > > > > > delusional > > > > > > denial state of existence, any chance you can take it a step > > > > > > further > > > > > > and answer the following? > > > > > > > Will the ripple eventually reach the Earth? If not then why not? > > > > > > > 'Hubble Finds Ghostly Ring of Dark > > > > > > Matter'http://www.nasa.gov/mission_pages/hubble/news/dark_matter_ring_featur... > > > > > > > "Astronomers using NASA�s Hubble Space Telescope got a > > > > > > first-hand view > > > > > > of how dark matter behaves during a titanic collision between > > > > > > two > > > > > > galaxy clusters. The wreck created a ripple of dark matter, > > > > > > which is > > > > > > somewhat similar to a ripple formed in a pond when a rock hits > > > > > > the > > > > > > water." > > > > > > > The ripple will eventually reach the Earth and this is evidence > > > > > > dark > > > > > > matter exists from the galaxy cluster to the Earth. This is > > > > > > evidence > > > > > > dark matter is the medium of space in which light waves > > > > > > propagate. > > > > > > > Pressure exerted towards matter by dark matter displaced by the > > > > > > matter > > > > > > is gravity.- Hide quoted text - > > > > > > > - Show quoted text - > > > > > > I have no idea, and this thread is abought the Einstein > > > > > Expansion.- Hide quoted text - > > > > > > - Show quoted text - > > > > > Androcles rechristened the space LT as "Einstein's expansion" > > > > formula: > > > > > xi = x'/sqrt(1 - v^2/c^2) with x' = x-vt > > > > 1905 paper. > > > > Used correctly, it transforms x coordinates of the same event > > > > between > > > > different frames, not lengths directly. Androcles plugs in lengths > > > > for > > > > xi, x' without considering what's involved in measuring a length. > > > > For > > > > a start, it involves measuring space coordinates at the *same* time > > > > and subtracting them from one another to get a length, if it's > > > > moving > > > > in that frame. If the end points remain at the same locations for > > > > all > > > > time, then simultaneity doesn't matter.- Hide quoted text - > > > > > - Show quoted text - > > > > Some ng history, Blackhead: > > > > This subject has been discussed often, and in some discussions > > > Androcles ha progressed all the way to a length comparison, following > > > Einstein's 1905 paper. I now believe he has got it all right except > > > for the final step, which is assigning values to x' and xi. He agrees > > > in the meaning of the variables x' and xi, including correctly that > > > x' < xi. Where he goes off the track is to insist that x'=L, and > > > therefore xi= Lgamma. The correct path is to assign xi=L and conclude > > > that x' = L/gamma. > > > > The absurdity of this error is the point of this thread. > > > > Uncle Ben- Hide quoted text - > > > > - Show quoted text - > > > I have been led through all this a few months ago, line at a time of > > the relevant section of the 1905 paper, by Androcles. Thank you > > Androcles. But my memory of the details have faded. > > > OK, so Androcles is finding that Einstein's beta is 2 for v = 0.866c. > > In other words, the length of a rod measured in frame k (using xi and > > tau) is twice as big as it would be if measured in frame K (using x > > and t). That's fine isn't it? > > The rod is stationary withinin frame k so its length is easily > > measured as L within frame k. (Einstein's paper uses x' instead of L.) > > So xi=L gives the rod length in frame k. > > Now what is the rod length in frame K? Since xi=2x, then x=0.5L. Ie > > we see the moving rod as shorter than it is measured in its rest frame.- > > Hide quoted text - > > > - Show quoted text - > > Yes, namesake, the length in k is twice the length in K. The question > is, are they 2L and L, or L and L/2. You (and everyone except > Androcles) correctly argue for the latter. > > The former is absurd, since there are many conceivable K's existing > simultaneously, each for a different v. For each, there is a different > length xi w.r.t. k, which requires that xi have many values > simultaneously. > > In the latter case, which you argue persuasively, xi is fixed at L, > and for conceivable K there is its own contracted x'= L/gamma. > > Uncle Ben- Hide quoted text - > > - Show quoted text - >OK, I see, the question is whether it is L and 2L or L/2 and L? The rest length L is the length at rest. >L cannot be measured with a ruler in frame K as the rod is moving in >frame K. No .. you can still measure it with a ruler .. you just need to see where it is on the ruler at some time. But it is easier in the rest frame, and in TAT frame you don't HAVE to look at wher it is against the ruler at a given time, as its position relative to the ruler does not change over time >So it must be measured within frame k, by someone in frame k, with say >a ruler. Its just a matter of (sensible) convention that we call the length of an object its rest length >Noone in frame k is going to measure it and say that it is 2 times 3 >feet long. They would instead say it is 6 feet long. L = 6 feet. > >In frame K the length of the rod is calculated as L/2 = 3 feet. Yes ... something Andy can't understand >I don't see where 2L arises as it does not occur in the calculation of >x (from a given a value of xi) and it is not a ruler measurement of >xi? It doesn't .. its one of andy's lies >It can only be 2L if the formula is used to calculate xi from a given >value of x, and that cannot happen as noone is in a position to >measure rod length x with a ruler in frame K (as th erod is moving) >and then apply the formula to calculate xi. xi is measured with a >ruler. x is calculated from the formula.
From: Inertial on 31 Jul 2010 18:49
"Androcles" wrote in message news:NBX4o.12907$Ds3.536(a)hurricane... >The rod is of length x' = x-vt in frame k Total nonsense. |