Is Length Contraction in SR physical??
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From: PD on 10 Feb 2010 09:39 On Feb 10, 8:06 am, kenseto <kens...(a)erinet.com> wrote: > On Feb 9, 5:56 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 9, 4:29 pm, kenseto <kens...(a)erinet.com> wrote: > > > > On Feb 9, 11:32 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 8, 2:58 pm, kenseto <kens...(a)erinet.com> wrote: > > > > > > On Feb 8, 3:25 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Feb 7, 8:39 am, kenseto <kens...(a)erinet.com> wrote: > > > > > > > > > When Ken started asking these questions 15 years ago, they were > > > > > > > > reasonable questions. When after a couple of years it was clear he was > > > > > > > > not listening to the answers given to his questions, the tone of the > > > > > > > > responses became a little different. > > > > > > > > Why should I listen to what you said when you did made sense.?? > > > > > > > Ken, it isn't wise to stop listening to people if you do not > > > > > > understand what they are saying. It would be important in that case to > > > > > > say, "I don't understand what you are saying. Can you explain it > > > > > > differently so I can understand it?" > > > > > > I don't listen to you because you keep on making contradictory claims. > > > > > For example the pole is physically contracted to fit the barn and at > > > > > the same time the pole does not fit into the barn because it is not > > > > > physically contracted. > > > > > Those are not contradictory claims. > > > > Yes they are. > > > > >Those are different accounts made > > > > in different reference frames. There is no requirement that the > > > > accounts be identical in different reference frames, and therefore > > > > they are not contradictory. > > > > They have to agree whether the physical length of the pole can fit > > > into the shorter barn. > > > No, they do not. There is no such requirement. > > There is the requirement that if you claim physical contraction then > the pole is really contracted I have no idea what you mean by "really contracted". It is physically contracted in one frame because it actually fits between the doors when the doors are closed. How can that be called anything other than physical? It does NOT mean *materially* contracted though -- as in squeezing or cooling. You get so confused about terms like "physically contracted" and "materially contracted" and "really contracted", as though they all mean the same things. They do not. The sooner you learn the distinctions, the better. >.....IOW, not just a geometric projection > effect. > > > > > > The physical length cannot fit into the barn is > > > an absolute concept and it is not observer dependent. > > > I'm sorry, Ken, that is just wrong. > > It is not wrong....also assertion is not a valid arguement. Factual matters are decided by documented facts, not argument, Ken. The point is not to *convince* you that you are wrong. I'm only pointing out when you ARE wrong, and I'd be happy to direct you to where you can look up the documented facts. However, there is no point in trying to convince you that you are wrong by making a compelling argument. I might as well be arguing with a stone pig. > > > > > > > Nor is it contradictory to say that a falling ball has a straight-line > > > > trajectory AND a parabolic trajectory in the same fall. Galileo knew > > > > that. I don't see why you don't understand that. > > > Do you understand what I wrote in this paragraph? Do you see why this > > is also not a contradiction? > > What you are describing here is a geometric projection of a falling > ball in the ship from the shore observer's point of view No, it is a PHYSICAL shape of a trajectory. That is the point. The straight line path is a PHYSICAL trajectory. The parabolic path is a PHYSICAL trajectory. The falling ball has BOTH a straight line physical trajectory AND a parabolic physical trajectory, as seen in different frames. What is *measured* is physical. >....this is > not the same as in the barn and the pole paradox where you claimed > that the pole is physically contracted.
From: glird on 10 Feb 2010 11:03 On Feb 9, 1:57 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 9 Feb, 00:40, mpalenik <markpale...(a)gmail.com> wrote: > > What's really funny is that he had already decided there was a > > systematic error in all the experiments *before* reviewing any of the > > experiments. > > Also funny is that he seems to think you can have a theory that > > "explains" SR while giving different numerical predictions than SR > > (such as the prediction of length contraction). In what way is the prediction of length contraction different than SR? glird
From: glird on 10 Feb 2010 12:33 On Feb 9, 2:00 am, mpalenik <markpale...(a)gmail.com> wrote: > > All I am saying is if your have a theory that does not predict the > length contractions of SR, then it is not a theory that explains SR. > It is a different theory. So, you either have to agree that length > contractions as described in SR are correct or admit that your theory > is fundamentally different from SR and not merely an interpretation of > it. In SR, lengths deform by q, 0, 0 in X, Y, and Z, where q=sqrt(1-v^2/ c^2). Before reaching that LTE value in his STR paper, Einstein arrived at a more general set of deformations, q(p), p, p, in which p could have any value whatsoever. A theory that explains the latter set also explains the former set. Here's how: If moving lengths physically deform by qp, p, p in x, y, z, where x is the direction of motion, that means that for any value of p, lengths in X will be q shorter than those in the perpendicular directions. Accordingly, if p = 1 (as it does in the LTE of SR) then lengths contract by q in their direction of motion and not at all in the perpendicular Y and Z directions. Hence if p = 1 the deformation equations, x' = qpx; and y' = z' = px = pz reduce to x' = qx, y' = z' = y = z. Given the latter set of deformations, then lengths deform by q, 0, 0 in X, Y and Z, as the Lorentz TRANSFORMATION equations require. Note to readers: A "deformation" equation for length gives the relation between the size of length AB before and after it deformed. Example with v = .8c: If rAB = 1 before it deformed then r'AB = q x rAB = .6rAB = .6 after it deformed. A "transformation" equation gives the relation between a distance found by using a qp deformed length as a measuring tool compared to that identical distance found by using an undeformed length as a measuring tool. Example: A qp deformed meter rod will fit 1/qp times into a given distance. Hence if p - 1 the deformation relation, dx' = qdx, yields the transformation equation, dx' = dx/q, in which dx = x - vt is the distance being measured. (Androcles is the only one on these newsgroups who ALMOST found this out. Unfortunately for him, he thought Einstein's deformation equations were transformations. Therefore he mistakenly thinks that Einstein required a moving length to EXPAND and moving clocks to run FAST; both of which contradict the LTE. He then trumpets his defective opinion to the world, saying that EINSTEIN was a nitwit, when in fact it is Androcles himself who doesn't understand either Einstein or his equations, some of which actually ARE defective.) glird
From: Ste on 10 Feb 2010 14:36 On 10 Feb, 14:20, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 10, 8:05 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Feb 10, 12:21 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 9 Feb, 21:02, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 9, 12:26 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > Two trains are on adjacent tracks, going in opposite directions, > > > > > > though I say that only to deliberately reinforce an ambiguity here. It > > > > > > doesn't matter whether the trains are going at different speeds, and > > > > > > in fact it isn't even important if one of the trains is stopped, or in > > > > > > fact whether they are going in the same direction but one faster than > > > > > > the other. All that matters is that there is a relative velocity > > > > > > between them. > > > > > > > Two lightning strikes occur, drawn to the trains because of the > > > > > > friction of the air between the trains. In fact, one lightning strike > > > > > > leaves a scorch mark (a 1 cm spot, if you want to be precise) on > > > > > > *both* trains as it hits. The other strike leaves a scorch mark > > > > > > somewhere else on *both* trains. > > > > > > > The question now is, were the strikes simultaneous or not? > > > > > > > There is an observer on train A, and an observer on train B, and they > > > > > > are both looking out the window when the strikes occur. > > > > > > > They make the following observations: > > > > > > 1. The observer on train A sees the two lightning flashes > > > > > > simultaneously. > > > > > > 2. The observer on train B sees the flash from the front of his train > > > > > > before he sees the flash from the rear of his train. > > > > > > > Now, it is not yet possible to determine whether the strikes were > > > > > > simultaneous originally. We have more work to do. But I want to see if > > > > > > you have a picture in your head of what has transpired. > > > > > > I have a basic picture, yes. > > > > > OK, then. > > > > Let's now follow up these two observations above and couple them with > > > > more observations. > > > > 3. After the strikes, the observer on train A runs a tape measure from > > > > his location to the scorch mark of one strike and makes note of the > > > > number. Then he runs a tape measure from his location to the scorch > > > > mark of the other strike and makes note of the number. These numbers > > > > are equal. Note the scorch marks are on his train, but that's an > > > > undeniable marker of where the event WAS when the signal propagation > > > > began. > > > > Not really. If his train is moving, then the scorch marks will have > > > actually moved from the location of the event. > > > With respect to what is the train moving? In this reference frame, the > > train is not moving at all, though the other one is. I remind you that > > it is not stated, nor is it clear, whether both trains are moving or > > only one is. Nor does it matter, because even if the train is moving > > relative to the track doesn't guarantee that the train is moving in > > any absolute sense. For example, if the track itself were moving (say > > because the surface of the earth is moving) and the train is moving in > > the opposite direction, one could easily visualize that the train is > > not moving at all, even if the train is moving relative to the track. > > > This is a crucial point about reference frames. We are making > > statements about observations made IN THIS REFERENCE FRAME, and in > > this reference frame, the train is not moving, the scorch marks are > > not moving, and we can measure the speed of light in this reference > > frame. > > > > > 4. After the strikes, the observer on train B runs a tape measure from > > > > his location to the scorch mark of one strike and makes note of the > > > > number. Then he runs a tape measure from his location to the scorch > > > > mark of the other strike and makes note of the number. These numbers > > > > are equal. Note the scorch marks are on his train, but that's an > > > > undeniable marker of where the event WAS when the signal propagation > > > > began. > > > > I'm not sure I agree with this. > > > It is exactly the symmetric situation with train A. Since the strikes > > left marks on both trains, there is no reason to rule it out here if > > it was permissible on A. > > > > > 5. The observer on A runs some experiments to measure the speed of > > > > light and the isotropy of the speed of light (that it is the same in > > > > either direction), and finds that the signal speed is the same. (Note > > > > this isotropy would NOT hold if the signal were sound, for example.) > > > > And *how* does he measure this? > > > A variety of ways. You could, for example, follow the procedures used > > by experimenters as documented in the papers referenced on the first > > Google search return on "experimental basis for relativity". > > > > > 6. The observer on B runs some experiments to measure the speed of > > > > light and the isotropy of the speed of light (that it is the same in > > > > either direction), and finds that the signal speed is the same. (Note > > > > this isotropy would NOT hold if the signal were sound, for example.) > > > > > Given these *observations* 1, 3, and 5, what would the observer on > > > > train A conclude about the simultaneity of the original strikes? > > > > I must admit I don't have a clear enough picture of what is happening.. > > > This gedanken seems to presuppose the very thing in question, that is, > > > relativity. > > > No, it doesn't presuppose anything other than what is *actually > > observed* in experiment. I cannot underscore this enough. For example, > > the claims that both (5) and (6) are both true may seem > > counterintuitive. How can both trains measure the speed of light to be > > the same from both directions, if the trains are moving relative to > > each other? Certainly an aether-based theory would not hold this is > > true. Does this mean we are *assuming* relativity is true so that > > these statements are both true? No. Statements (5) and (6) are the > > results of *experimental observation*. Nature really does behave this > > way, even if we find it counterintuitive. > > > > Let's refine it a bit by stipulating that the Earth is stationary, the > > > track is stationary, and the clouds are stationary, > > > On what basis would you make such an arbitrary stipulation, when you > > KNOW that this is not the case? > > You may be tempted to say, "Because we have to have an absolute > > reference for stationary *someplace*, and we might as well make it > > Earth because we live here." A moment's thought will tell you this is > > foolish. Physical laws don't care where we live. Then, in the search > > for finding an absolute reference for rest, you may eventually ask > > yourself why such an absolute reference would be needed at all, > > especially if there is nothing you can clearly identify that would fit > > the bill... > > > > and we'll also > > > stipulate that the lightning strike happens in an instant (even though > > > it doesn't), and marks all locations at that instant. > > > > Now, where are the trains on the tracks when the lightning strikes, > > > and are they moving? > > > You see? You are trying to establish an absolute reference frame, even > > if it means doing so completely arbitrarily, JUST SO you can say > > whether the trains are absolutely moving or not. > > As a side note, let me just offer the word of encouragement that you > are asking all the right questions and wrestling with all the right > issues. In other words, this is what students do when they actually > learn something. You are on your way to really understanding what > relativity is saying, and also on your way to learning how to check > whether the claims that are made do in fact match experimental > observation. > > But as a cautionary note, let me also remind you that we are ONLY > trying to put together an understanding of where the frame-dependence > of simultaneity comes from, which is only one small stepping stone in > the exploration of special relativity, which in turn is itself a small > stepping stone in the exploration of general relativity. As you can > see, this takes work, and extended thinking, and asking lots of > serious questions. This is why many of the basic ideas in physics > cannot be explained compellingly in a few sentences to interested and > intelligent hobbyists. Physics students would be expected to discuss > this in class for about an hour, then think about it and work through > issues for about four or five hours outside of class (with other > students or with the teacher for some of that), before moving on to > the next stepping stone. Indeed. Btw, it's time for that embarassing climbdown on my part, that I referred to previously. I definitely can't make this aether theory work. For what I lack in mathematical skill, I've made up for with programming skill, and it is clear that propagation speed cannot be constant with reference to an absolute frame - its effects would be immediately obvious. The question therefore remains, how can the speed of propagation possibly be measured to be constant in all frames.
From: kenseto on 10 Feb 2010 17:57
On Feb 10, 9:39 am, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 10, 8:06 am, kenseto <kens...(a)erinet.com> wrote: > > > > > > > On Feb 9, 5:56 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Feb 9, 4:29 pm, kenseto <kens...(a)erinet.com> wrote: > > > > > On Feb 9, 11:32 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > On Feb 8, 2:58 pm, kenseto <kens...(a)erinet.com> wrote: > > > > > > > On Feb 8, 3:25 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > > On Feb 7, 8:39 am, kenseto <kens...(a)erinet.com> wrote: > > > > > > > > > > When Ken started asking these questions 15 years ago, they were > > > > > > > > > reasonable questions. When after a couple of years it was clear he was > > > > > > > > > not listening to the answers given to his questions, the tone of the > > > > > > > > > responses became a little different. > > > > > > > > > Why should I listen to what you said when you did made sense.?? > > > > > > > > Ken, it isn't wise to stop listening to people if you do not > > > > > > > understand what they are saying. It would be important in that case to > > > > > > > say, "I don't understand what you are saying. Can you explain it > > > > > > > differently so I can understand it?" > > > > > > > I don't listen to you because you keep on making contradictory claims. > > > > > > For example the pole is physically contracted to fit the barn and at > > > > > > the same time the pole does not fit into the barn because it is not > > > > > > physically contracted. > > > > > > Those are not contradictory claims. > > > > > Yes they are. > > > > > >Those are different accounts made > > > > > in different reference frames. There is no requirement that the > > > > > accounts be identical in different reference frames, and therefore > > > > > they are not contradictory. > > > > > They have to agree whether the physical length of the pole can fit > > > > into the shorter barn. > > > > No, they do not. There is no such requirement. > > > There is the requirement that if you claim physical contraction then > > the pole is really contracted > > I have no idea what you mean by "really contracted". It is physically > contracted in one frame because it actually fits between the doors > when the doors are closed. How can that be called anything other than > physical? It does NOT mean *materially* contracted though -- as in > squeezing or cooling. Contraction by cooling is "really physically contracted", or "materially contracted", and it is NOT a geometrically contracted effect. IOW, when a meter stick is "really physically contracted" or "materially contracted" its physical length or material length is "physically" or "materially" shorter than the observer's meter stick. I don't understand why you insist on hijacking the word "physical" and give it a different meaning than the standard meaning. I don't understand why you don't except the correct phrase that length conraction in SR is a "geometric projection effect". BTW the physical length or material length of the pole DOES NOT actually fits between the doors when the doors are closed. The *geometric projection* of the pole can fit into the barn with both doors are closed.....the reason is that geometric projection is not physical or material. Ken Seto > > You get so confused about terms like "physically contracted" and > "materially contracted" and "really contracted", as though they all > mean the same things. They do not. The sooner you learn the > distinctions, the better. > > >.....IOW, not just a geometric projection > > effect. > > > > > The physical length cannot fit into the barn is > > > > an absolute concept and it is not observer dependent. > > > > I'm sorry, Ken, that is just wrong. > > > It is not wrong....also assertion is not a valid arguement. > > Factual matters are decided by documented facts, not argument, Ken. > The point is not to *convince* you that you are wrong. I'm only > pointing out when you ARE wrong, and I'd be happy to direct you to > where you can look up the documented facts. However, there is no point > in trying to convince you that you are wrong by making a compelling > argument. I might as well be arguing with a stone pig. > > > > > > > > Nor is it contradictory to say that a falling ball has a straight-line > > > > > trajectory AND a parabolic trajectory in the same fall. Galileo knew > > > > > that. I don't see why you don't understand that. > > > > Do you understand what I wrote in this paragraph? Do you see why this > > > is also not a contradiction? > > > What you are describing here is a geometric projection of a falling > > ball in the ship from the shore observer's point of view > > No, it is a PHYSICAL shape of a trajectory. That is the point. The > straight line path is a PHYSICAL trajectory. The parabolic path is a > PHYSICAL trajectory. The falling ball has BOTH a straight line > physical trajectory AND a parabolic physical trajectory, as seen in > different frames. What is *measured* is physical. > > > > >....this is > > not the same as in the barn and the pole paradox where you claimed > > that the pole is physically contracted.- Hide quoted text - > > - Show quoted text -- Hide quoted text - > > - Show quoted text - |