Known physics defeated by simple puzzle?
in [Relativity]
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From: Edward Green on 10 Apr 2010 15:35 On Apr 6, 7:30 pm, Timo Nieminen <t...(a)physics.uq.edu.au> wrote: > On Tue, 6 Apr 2010, Edward Green wrote: > > On Apr 6, 11:39 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > It isn't difficult for me. I can explain it, in its entirety, in terms > > > of a "visual effect" and the careful timing of the doors. It's other > > > people here who keep insisting that it is not a visual effect, and > > > hence the fuss > > > Taking you at your word (that you can explain it), I wonder if your > > "visual effect" is not an alternate formulation of SR. But perhaps > > that has been ruled out already. > > No, "visual effect" isn't an alternative formulation. But it's easy to get > the idea that it is from the language used, especially that Most Evil > Word, "observer". > > The usual usage of "observer" in SR means "coordinate system" or > "reference frame", not "somebody who sits there and looks around" which we > might expect from other usage of the term. "As seen by observer X" means > "as measured using synchronised clocks in coordinate system X". The > coordinate system extends over all space, and the question of "where is > the observer located" doesn't apply. So, it doesn't matter where the > observer sits on the ladder or stands in the barn, or at which door they > stand, since "observer" doesn't mean that kind of real observer. Yes, I knew that. :-) Sloppy thinking on my part to suggest otherwise. > That said, it's quite possible to include real observers, who sit and look > around, in SR, taking the finite propagation speed of signals into > account. You get interesting optical effects. > > Exercise for the reader: Consider a pole of length L, moving directly > towards or away from an observer (a real observer!) at speed v. > > 1. What is the length L' of the pole, as measured in a coordinate system > in which the observer is at rest (i.e., the observer's rest frame)? Does > this depend on whether it is moving towards or away from the observer? Why > or why not? This is a trick question. The length of the pole is L_0/gamma either way; as you say, it doesn't matter where the "observer" is in his rest frame. > 2. How long does the pole appear to be when the observer _looks_ at it? > (We can assume there are little flags or lights on the ends, so that the > ends can be clearly seen). What is this apparent length for motion towards > and away from the observer? Let the pole be approaching the observer with speed v towards the origin, and without loss of generality, let the near end of the pole be at the origin of space and time coordinates, (0,0) (imagine the observer is somewhere down the negative x axis). The locus of points where a photon emitted towards the observer will wind up coincident with one emitted by the near end of the pole is x = -ct . Now, as a function of time, the locus of location of the far end of the pole is x = -vt + L, where L is the Lorentz contracted length. Setting these two loci equal and solving for x we find x = cL/ (c - v). So the pole appears longer by a factor which acts opposite to the sense of Lorentz contraction. It may just cancel at a critical velocity, I haven't figured that out. If the pole is receding from the observer, then unless I am very much mistaken we simply change the sign of v, so that x = cL/(c + v). So in this case the finite propagation speed of light works to enhance the apparent contraction. > 3. Can the observer see the Lorentz contraction of the pole? Not cleanly.
From: Sue... on 10 Apr 2010 16:21 On Apr 10, 1:21 pm, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 9, 5:46 pm, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > > > > > On Apr 9, 6:10 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Apr 9, 5:01 pm, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > > > > > On Apr 9, 5:03 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > On Apr 9, 3:28 pm, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > > > > > > > On Apr 9, 3:52 pm, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > > On Apr 9, 2:32 pm, "Sue..." <suzysewns...(a)yahoo.com.au> wrote: > > > > > > > > > On Apr 9, 10:57 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > > > > On Apr 8, 9:09 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > > > > On 8 Apr, 15:10, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > > > > > > On Apr 7, 10:32 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > > > > > It's awfully difficult to misinterpret the numerical value of a > > > > > > > > > > > measurement and whether it agrees with the numerical value of another > > > > > > > > > > > measurement. > > > > > > > > > > > No, because if I say relative to me A is moving at 10kmh and B is > > > > > > > > > > moving at 20kmh, and you say that relative to you A is moving at > > > > > > > > > > 20kmh, and B moving at 30kmh, then despite the numerical difference of > > > > > > > > > > speeds we both agree about the movement of A relative to B. > > > > > > > > > > But that is not what happens. > > > > > > > > > For example, if I see a car traveling west at 10 kmh, and a car > > > > > > > > > traveling east at 35 kmh, then you have the expectation that, to a > > > > > > > > > passenger riding in the car traveling east, the other car is traveling > > > > > > > > > 45 kmh west. > > > > > > > > > But in fact, it is not traveling at 45 kmh west to a passenger in that > > > > > > > > > car. > > > > > > > > > It is traveling at something close to that, but only approximately. > > > > > > > > > ========================== > > > > > > > > > > The bottom line is, the basic sum rule you've been taught for relative > > > > > > > > > velocities is a LIE. > > > > > > > > > << The main types of particle combinations used at RHIC > > > > > > > > are p + p, d + Au, Cu + Cu and Au + Au. The projectiles > > > > > > > > typically travel at a speed of 99.995% of the speed of light > > > > > > > > in vacuum. For Au + Au collision, the center-of-mass > > > > > > > > energy \sqrt{s_{NN}} is typically 200 GeV > > > > > > > > (or 100 GeV per nucleus); >> > > > > > > >http://en.wikipedia.org/wiki/Relativistic_Heavy_Ion_Collider > > > > > > > > Yes, and the energy adds. The velocities don't. You DO know the > > > > > > > difference, don't you? > > > > > > > No, I suppose not. > > > > > > > Wouldn't a calculation from the relative velocities > > > > > > demonstrate your point better than an insult? > > > > > > > Pseudoscience appeals to false authority, to emotion, > > > > > > sentiment, or distrust of established fact. > > > > >http://www.quackwatch.org/01QuackeryRelatedTopics/pseudo.html > > > > > > > A couple of your fellow Lorentz ether theorists > > > > > > seem to be having the same problem so perhaps > > > > > > it is worth looking into. > > > > > > > Sue... > > > > > > > > > > PD > > > > > > That's fine. > > > > > > For starters, your quote above is incorrect and needs to be updated. > > > > > See your own wiki link for the correction. The energy is 100 GeV per > > > > > *nucleon*, not per *nucleus*. > > > > > Thank you. I just flagged it for update. > > > > > > A gold nucleus has an atomic mass of 196.96655 amu, and an amu is > > > > > 931.494028 MeV. > > > > > So the gold nucleus rest energy is 183.473165 GeV. > > > > > Therefore a gold nucleus with energy 100 GeV/nucleon corresponds a > > > > > relativistic gamma factor of 107.354. > > > > > From this, the speed of the nucleon can be calculated from beta^2 = 1 > > > > > - 1/gamma^2, from which we find that beta = 0.999957, in agreement > > > > > with the number that's in the wiki article. > > > > > > For two particles closing each at beta in the lab, the relative > > > > > velocity is given by > > > > > beta_rel = 2beta/(1+beta^2) = 99.999999906% of c. > > > > > That corrects for *our* observation, not > > > > the particle's observation. > > > > No, that's not correct. The *relative* velocity is the velocity of one > > > particle as seen by the other. This is not the velocities of the > > > particles as seen in the lab, which has already been pointed out is > > > 99.9957% of c. > > > > > Colliers would be no better than single > > > > beams otherwise. > > > > Relative velocity is not the figure of merit, and not the reason to > > > build colliders vs fixed target machines. Center of mass energy is. > > > And I showed you how to do that calculation, and I also gave you a > > > reference that shows you the formulas you should use, including > > > applications in both cases. Please read them. Note that in a fixed > > > target experiment, one of the p's (say, p2) is zero, and so the vector > > > sum of the momentum is not zero, and so the center of mass energy is > > > reduced, compared to a collider experiment where |p1+p2| = 0. > > > > > > The center of mass energy squared is given by the relation > > > > > (E1+E2)^2 - |p1+p2|^2, where the first sum is a scalar sum and the > > > > > second is the scalar magnitude of a vector sum. Here, since p2 = -p1, > > > > > the vector sum trivially adds to zero, and so leaves only the first > > > > > term, which is (100 GeV + 100 GeV)^2 = (200 GeV)^2. Hence the center > > > > > of mass energy is 200 GeV, while the relative velocity between the two > > > > > is 99.999999906% of c. > > > > > That is calculated, not measured. > > > ================ > > > > No, it is measured. It is measured by virtue of the fact that the > > > measured cross sections and decay distributions are identical in cases > > > where the relative velocity of the particles in a collider environment > > > is identical to the relative velocity of the particles in a different > > > fixed target environment. Relativistic kinematics has been > > > experimentally tested and confirmed through *measurement*. It is not > > > just hypothetical stuff. ============= > > > <<Results 1 - 10 of about 170 for > > "measured cross sections" "decay distributions" > > velocity.>> (c) Google > > Can't find what I suggested? Too reliant on your dim abilities to do a > web search? > I didn't question it further. I sent your analysis to my legislators with the suggestion they end all pubic funding of collider facilities and put the money into something useful like time machines and barn stretchers. :-)) Sue... > > > > The B.S. meter is getting into the red zone and > > you are doing a miserable job of selling > > a collider to the tax payers. Is it because > > you would rather sell them a time-machine? > > > <<Pseudoscience displays an indifference to facts. > > Instead of bothering to consult reference works > > or investigating directly, its advocates simply > > spout bogus "facts" where needed >> http://www.quackwatch.org/01QuackeryRelatedTopics/pseudo.html > > > Sue... > > > > > I hear the > > > > Alpine mountaineer that volunteer to ride > > > > the ion with a police radar had to cancel due > > > > to illness in his dairy. > > > > > > All of these calculational formulas are found in public archives, > > > > > which you should take care to bookmark, read, and learn how to use, > > > > > since it is plain that you don't know what you're doing when you look > > > > > at a wiki article and incorrectly quote it, let alone derive incorrect > > > > > conclusions from it. If you need help, let me point you to > > >http://pdg.lbl.gov/2009/reviews/rpp2009-rev-kinematics.pdf > > > > > Oh! The nukeular-option. Jackson. > > > > That is not from Jackson, though it borrows from it. It is a > > > compendium compiled by the PDG group. It is standard relativistic > > > kinematics. If you want another source that gives a second opinion > > > about relativistic kinematics, I'm happy to suggest a number of books.. > > > The one by Don Perkins is a good start, as is the one by Ferbel and > > > Das. > > > > > I don't argue much with him. > > > > > Still the collision formula from a lab frame > > > > doesn't help parlour tricks like pole and barn > > > > > Replace the CW ion with a pole. Replace the CCW > > > > ion with a barn and they get the same gamma. > > > > > If they were not seen to fit at rest. > > > > They will not be seen to fit in the > > > > RHIC or LHC lab frame. > > > Sue... > > > > > Sue... > >
From: Ste on 10 Apr 2010 23:19 On 10 Apr, 13:05, "Inertial" <relativ...(a)rest.com> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > news:db82a4dc-e7c6-4fea-a210-145c805688ef(a)z11g2000yqz.googlegroups.com... > > > > > > > On 10 Apr, 12:24, "Inertial" <relativ...(a)rest.com> wrote: > >> "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >>news:25a765b8-2e31-476f-9935-34014a09438f(a)y17g2000yqd.googlegroups.com.... > > >> > On 10 Apr, 11:20, "Inertial" <relativ...(a)rest.com> wrote: > >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> >> >> > based on > >> >> >> > the relative speed between the clocks? (and not based on the > >> >> >> > direction > >> >> >> > of relative movement?) > > >> >> >> Yes. I've already said that. > > >> >> > So what is the extent of the slowing, and on what variables does it > >> >> > depend? (We can speak in quantitative terms on this point.) > > >> >> It depends on the speed. The greater the speed, the larger the effect > >> >> (see > >> >> the gamma factor). That affects the measured clock ticking rate and > >> >> the > >> >> measure length of a moving object. There is also the effect on > >> >> simultaneity. > > >> >> Its all given by the Lorentz transforms. > > >> > Indeed. So there is always a slowing, related to speed, no matter what > >> > relative direction the object may be travelling in. > > >> Yes > > >> > In other words, if > >> > an object is approaching you at .9c, it displays a slowing that is the > >> > same as if it were receding at .9c? > > >> Yes > > >> If by 'displays' you are not including any optical/visual/etc illusions > >> due > >> to propagation delays etc. > > > Yes, I had assumed we'd accounted for those already, and are > > disregarding those effects. > > >> And if by 'slowing' you mean that observers at rest in your frame of > >> reference would measure its ticking rate as slower. > > > Ah, I've just realised another question. I was assuming that we're > > talking about a fixed amount of "lag" in distant clock. Is that what > > you're talking about, or are you talking about an *ongoing* loss of > > time? In other words, the longer the distant clock is moving, the more > > its time lags behind that of the local clock (and, yet, all this lag > > is recouped when the two clocks return to relative rest). > > The 'lag', as you call it, is distance and velocity dependent. When there > is no distance between them and no difference in motion, there is no 'lag'. Yes, but the important thing (for me) to clarify is that, even if there is only a negligible distance between them, if there is a relativistic difference in velocity, then there will still be a fixed amount of time lag?
From: Peter Webb on 11 Apr 2010 00:12 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:996ae2ac-6e26-46b4-9e71-21242c60c54c(a)30g2000yqi.googlegroups.com... On 10 Apr, 13:05, "Inertial" <relativ...(a)rest.com> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > news:db82a4dc-e7c6-4fea-a210-145c805688ef(a)z11g2000yqz.googlegroups.com... > > > > > > > On 10 Apr, 12:24, "Inertial" <relativ...(a)rest.com> wrote: > >> "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >>news:25a765b8-2e31-476f-9935-34014a09438f(a)y17g2000yqd.googlegroups.com... > > >> > On 10 Apr, 11:20, "Inertial" <relativ...(a)rest.com> wrote: > >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> >> >> > based on > >> >> >> > the relative speed between the clocks? (and not based on the > >> >> >> > direction > >> >> >> > of relative movement?) > > >> >> >> Yes. I've already said that. > > >> >> > So what is the extent of the slowing, and on what variables does > >> >> > it > >> >> > depend? (We can speak in quantitative terms on this point.) > > >> >> It depends on the speed. The greater the speed, the larger the > >> >> effect > >> >> (see > >> >> the gamma factor). That affects the measured clock ticking rate and > >> >> the > >> >> measure length of a moving object. There is also the effect on > >> >> simultaneity. > > >> >> Its all given by the Lorentz transforms. > > >> > Indeed. So there is always a slowing, related to speed, no matter > >> > what > >> > relative direction the object may be travelling in. > > >> Yes > > >> > In other words, if > >> > an object is approaching you at .9c, it displays a slowing that is > >> > the > >> > same as if it were receding at .9c? > > >> Yes > > >> If by 'displays' you are not including any optical/visual/etc illusions > >> due > >> to propagation delays etc. > > > Yes, I had assumed we'd accounted for those already, and are > > disregarding those effects. > > >> And if by 'slowing' you mean that observers at rest in your frame of > >> reference would measure its ticking rate as slower. > > > Ah, I've just realised another question. I was assuming that we're > > talking about a fixed amount of "lag" in distant clock. Is that what > > you're talking about, or are you talking about an *ongoing* loss of > > time? In other words, the longer the distant clock is moving, the more > > its time lags behind that of the local clock (and, yet, all this lag > > is recouped when the two clocks return to relative rest). > > The 'lag', as you call it, is distance and velocity dependent. When there > is no distance between them and no difference in motion, there is no > 'lag'. Yes, but the important thing (for me) to clarify is that, even if there is only a negligible distance between them, if there is a relativistic difference in velocity, then there will still be a fixed amount of time lag? ________________________________ SR does not impose a fixed "time lag". It says that clocks in different inertial frames run at different "rates". This has nothing to do with the relative position, only the relative speed. In the twins paradox, the difference in ages when the twin returns could be considered the "lag". If the travelling twin travels twice as far and returns, then the difference in ages (the lag) will be twice as much when he returns. These relativistic effects are all functions of relative speed, and relative position doesn't enter into it. A ladder travelling close to c will still be shorter than the barn, whether it is within the barn or 1,000 kms away.
From: NoEinstein on 11 Apr 2010 00:28
On Apr 8, 10:07 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 8 Apr, 15:02, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > > On Apr 7, 10:21 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > Remember the ladder is moving relative to the barn. > > > > How does one determine that the ladder is contained completely inside, > > > > exactly? > > > > By shutting the doors at the same time, of course. > > > Yes, indeed, this is a crucial ingredient. And of course if the doors > > were not shut at the same time, then we would not say that the first > > object fit inside the second object, would we, even though otherwise > > the observations would be the same? That is, if the front of the > > ladder were inside the barn (having verified that it passed through > > one but not the other door) when one door was shut, and the back of > > the ladder were inside the barn (by the same verification) when the > > other door was shut, this would be no indication that the ladder fit > > inside the barn, right? Especially if the doors were not shut at the > > same time. > > Indeed. The question, really, is not whether the ladder fits inside > when the doors are actually shut, but whether it *would* fit if they > *were* shut. As I say, I don't think we need to discuss extensively > what "fitting" means - but for completeness, it simply means whether > the full extent of the ladder could be at once contained within the > confines of the barn. > > > So, jumping to the chase, if in one reference frame, it is established > > that the doors were shut at the same time, then the definition of > > "fitting" inside the barn would have been met, and the ladder would > > have fit inside the barn in that frame. If in another reference frame, > > it is established that the doors were not shut at the same time, then > > the definition of "fitting" inside the barn would not have been met, > > and the ladder would not have fit inside the barn in that frame. So, > > you see, it is entirely possible -- and indeed we would be forced to > > this conclusion -- that the ladder fits in the barn (by virtue of your > > own definition) in one frame and does not fit in the barn in another > > frame, provided that we can establish that the timing of the doors > > being shut depends on the frame. > > Yes, but this is a contradiction in reality, so the only other > explanation is that perhaps it *appears* to do this, but does not > actually do so. And of course, my money would be that nothing changes > real length at all, Bravo for you! NoEinstein >and that the appearance of this is an illusion > that can be explained somehow in terms of the behaviour of the > electromagnetic interaction (possibly combined with a > misinterpretation of what relativity actually describes, and an > ignorance of the mechanisms underlying the effects of relativity).- Hide quoted text - > > - Show quoted text - |