Bullshit! Did you even read the explanations I linked to? One more time: General Relativity is not needed to resolve the twin paradox! How much clearer do you need to be told?!?
So you accept local Lorentz invariance? Good for you! So. What. That doesn't mean that SR isn't able to resolve it. It just shows the non-symmetry of the situation; how three inertial frames are involved and not two. But all SR needs to conclude that one twin accumulates less proper time than the other between their two meetings is their worldlines through one inertial frame. Then their path lengths (wrt. the Minkowski metric) can be calculated, and since their first and second meetings are unique spacetime events, comparison of the lengths will make sense. We find that the paths are timelike, and especially, we find that the length of the stay-at-home twins worldline is exactly the spacetime interval between those two events. We can now conclude from the fact that their paths were different, that the travelling twins proper time between the events is less than the proper time of the stay-at-home twin, because a timelike worldline between two spacetime events with the length of the spacetime interval is the one with the maximal proper time between those events, as easily seen from the shape of the Minkowski metric. No GR, nor indeed anything about acceleration, necessary.
Yes. Not a totally accurate statement. Mathematical cnsistancy would not create paradoxes only if mathematical consistancy matches meperical findings.
Speaking of not reading. I repeat this fucking Twin Paradox is not at issue. It is a straw arguement dodge. In constrast to your efforts to change the subject and conceal the truth regarding SR itself let me post a specific example. Relativity is used to compute simultaneity shift of a rocket accelerating to some pre-established relative velocity to a deep space space station. Relativity is used to compute a space station based time period aboard the rocket considering time dilation per relativity from the stations view point to produce a one hour clock tick rate test. The velocity choosen is 0.866c such that gamma equals 2 and the clock aboard the rocket should record only 50% of the time compared to the station based clock. The test is performed based on prelaunch computations using relativity and: 1 - Do you agree that the test can be started/stopped simultaneously? (this means in a universal sense such that any perception delays of the events are taken into consideration). 2 - In contrast to #1 above that simultanety is not of a consideration since the test is for a given time period according to space station based clocks and does not require simultaneous start/stop events? 3 - Do you agree that the clock tick rate test (and accumulated time) tests time dilation only during periods of inertial relative velocity.? 4 - Do you agree that there are no "turnaround" acceleration/deceleration, blue shift/red shift considerations in the test? 5 - Do you agree that there are no GR considerations in this test of time dilation according to SR relative velocity formulas? 6 - Do you agree that the rocket clock only records 30 minutes for the test.? 7 - Do you claim that the space station clock will only record 15 minutes since the rocket recorded 30 minutes and according to SR (and you) the station has a velocity of 0.866c and its clocks must be ticking at half the rate of the rocket clocks? 8 - Do you acknowledge that the claim of time dilation due to relative velocity between the space station and rocket has not caused the space station clock to meet SR predictions of time dilation? If you answer "NO" to any of the above please give a completely detailed explanation of how you justify that response. Please Register or Log in to view the hidden image!
Not in general, no. Let's see why: Assume that the rocket r's rest frame R and the space stations s's rest frame S coincide on the origin, i.e. let (x,t) from S and (x',t') from R describe the same event when x=x'=0, t=t'=0, and let that event be "the rocket leaves the space station with speed 0.866c". Now, in the S frame the spacetime position of the rocket is described by r(t) = (vt,t), and the spacetime position of the spacestation is described by s(t) = (0,t). Now, we can start the clocks simultaneously as viewed from both frames exactly at (x,t)=(x',t')=(0,0) only because this is a single spacetime event. If the clocks did not occupy the same point in space time, then they would not agree on simultaneity. The reason for this is the same is why they won't agree on when the experiment stops: At time t=3600 in the S frame we have the following spacetime coordinates of r and s (letting c=1 for simplicity): r(3600) = (0.866*3600, 3600) s(3600) = (0,3600) Clearly, these events are simultaneous in S. Now, transform these via the Lorentz equations to find which spacetime coordinates these two events correspond to in R: r(3600) transforms to (x',t')=(0,γ(3600-0.866<sup>2</sup>*3600)) s(3600) transforms to (x',t') = (γ(-0.866*3600),γ(3600)) The time coordinates of these two events are clearly different, hence they are not simultaneous in R. This applies to any non-zero t, hence you can never stop the clocks so that both s and r agree that they were stopped simultaneously. Not understood. If you want to assume relative velocity, and not consider acceleration, just do so. I did, above. Sure. No problem here. Let's check: 2(3600-0.866<sup>2</sup>*3600) = 1800 Fine. No, As viewed from S, the r clock recorded 30 minutes exactly when the s clock recorded 1 hour. Yes. As viewed from R, the r clock reads 30 minutes when the s clock reads 15 minutes. To check this transform (x,t)=(0,900) (the S coordinates corresponding to the event "s's clock reads 15 min.") to R. You'll find that it gives an R-time coordinate t'= γ(900-0.866c*0) = 1800. So, indeed the s clock is dilated as seen from R, and the r clock is dilated as seen from S. No. The prediction of SR is: When s turns off his clock at S time 3600s, s will claim that r's clock reads 1800s. r on the other hand will claim that when s turns off his clock, then r's clock reads 7200s. The math for this being what SR predicts is in the reply to 1). SR doesn't make the prediction "When 60 s minutes have passed then 30 r minutes have passed, and when 30 r minutes have passed then 15 s minutes have passed; hence when 60 s minutes have passed then 15 s minutes have passed", which is what you seem to be saying that SR should predict. The key to why this phrase is wrong is that there's a hidden simultaneity in "when". This phrase treats events that are pair-wise simultaneous in two different frames ((60s,30r) is simultaneous in S, (30r,15s) is simultaneous in R) from two different frames as all being simultaneous in S frame. But simultaneity isn't transitive between frames in SR, and this thought experiment proves why not. Done and done. Remember, MacM, the Lorentz equations are the final arbiter on what SR predicts. The time dilation formula falls out of the equations, but it must be applied in the right way. If you had actually sat down and done the full math on this scenario, then you would have found out that the supposed contradiction is only in your head. Why do you never do that?
In the experiment* described in thread, "Is time universal? - No, and it proof," there are no "perception delays" yet the simultaneous explosions in the train's frame are not simultaneous in ANY other frame, including the ground frame. _________________________________________Experiment Design: *Train has very small bombs at front and rear, triggered by light flash originating at center of train (equally distant from each bomb). On ground, along side of the track, are millions of close-spaced stop watches, two of which are stopped by the small explosions that occurs only microns from their stop switches. Bombs stick out from side of train and miss all of the synchronized ground clocks by microns as they pass. A simple experiment with NO "PERCEPTION DELAYS". NO HUMAN "OBSERVERS", until weeks later when the return to see the time shown on the two stopped stopwatches. The stopwatch that was adjacent to the train's rear bomb stopped before the one adjacent to the front bomb. (This because while the light was on it way to the bombs, in the ground frame, the rear bomb was advancing to meet it and the front bomb was moving away from the advancing light, but not as fast as the light was advancing to catch the bomb.) Your have introduced many "duck" and "weave" irrelevant facts (or fictions) to deny that: EVENTS SIMULTAMNEOUS IN ONE FRAME ARE NEVER SIMULTANEOUS IN ANOTHER FRAME. Among your irrelevant "duck-and-weave" posts, trying to deny the obvious, you discuss "time dilation", "length contraction." Different "tick rates" and even location of "bomb craters" relative to the light flash origin! Here you ask others to agree that: Except for "perception delays", events simultaneous in one frame are simultaneous in all frames. - You still do not understand, do you? Please Register or Log in to view the hidden image!
Well, this is as close as we are probably ever going to get to an agreement so I consider the relativity argument effectively finished. I personally think that attacking the special case of any given theory and not considering the general case of the theory is a little silly. In several ways it is similar to attacking classical mechanics because Newton's first law doesn't work in dynamic situations, without considering that the first law is merely a special case of the more general second law. But that is certainly your perogative, and given your desired strict separation of SR and GR I can see how you can reach the conclusion that SR is insufficient. I think Einstein agreed that SR was incomplete (even if not due to this particular example then certainly with many other examples) and that is why he spent so much effort in generalizing it. I would like to go back to the Bremsstrahlung discussion, because it is an interesting phenomenon that I had not previously considered in detail. I think I understand now how to identify the situations and frames where photons will be radiated. What you need is a time-varying electromagnetic field. So, in the case of the superconductor there is no electric field and the magnetic field is constant. Hence no radiation which agrees with the observation that there is no energy loss. Now consider just the electric fields for a moving charged particle being deflected by a stationary electric field. A stationary detector will see the stationary field as time invariant and will see the particle's field as time varying, therefore a stationary detector will detect radiation. A detector co-moving with the particle will see the particle's field as time invariant and will see the stationary field as time varying, therefore a moving detector will also detect radiation. So qualitatively it seems that the various observers will agree. I don't know if that is a general conclusion or if it only applies to the experiment I just described. -Dale
Nice and consice. It aplies for any motion considered only from the "rest frame" of the two meetings, which is an inertial frame. -Dale
to funkstar: I a not strong enough on "shape of the Minkowski metric" to work this out for myself, but fully understand you and, like Dale, think this an excellent point. It is not just the particular trip of the traveling twin but ANY path thru space time other than that of the stay at home twin, which has less proper time and this falls out of the metric. Thanks and congratualtions.
Funkstar, Not a very definitive answer. It is either Yes or No. You have commited errors already. I specified that relativity was used to compute the simultaneity shift, so any discussion about frames of referance and event times is not at issue. Once again. 1 - Can relativity be used to compute simultaneity shifts? 2 - Having computed such shift can one cause events to defacto occur simultaneously in a universal sense? (that is perception by remote observers after computing information propogation delays and time dilation shifts, etc., result in the conclusion of the observer that indeed the events were simultaneous). Blatantly false. Because we are not talking about what they each see. I stipulated prelaunch calculation of simultaneity shift and subsequenct timing in each rame such that computation would show the observer that the events were defacto simultaneous even though they would not appear simultaneous to the observer. Compute the simultaneity shift and compensate the timing of the events in each frame such that they are defacto simultaneous - Not that they are observed or percevied simultaneous. That is not the issue. Here is where you screw up. You are mixing perception with reality. The physical clocks only accumulate one set of data. It is not frame dependant. Only perception including delays, etc can be different. Accumulated time is one hour on A and 30 minutes on B and no frame of referance can change that relationship. Acknowledging that you must now acknowledge that that fact defies the SR mathemaitcal prediction that A is running slower than B. IT IS NOT. It actually ran twice as fast as B, just as logic suggest it should and that fact is what is recorded by the accumulated times on the clocks. In A's frame it accumulates 60 minutes and at the same time in B's frame it has accumulated 30 minutes. It is now absurd to try and argue that in B's frame when it has reached 30 minutes that A will have accumulated 15 minutes. Isn't it? Arguements about frames of referance or simultaneity are straw dodge arguements which do not actually resolve this disparity between the mathematical predictions of SR and the fact of emperical data. Sorry no transforms necessary. We have established above that A has physically accumulated 60 minutes at the instant B has accumulated 30 minutes. No other mathematical predictions can be valid, nor are they supported by emperical data. Only the fact of B being time dilated since it accelerated is supported by data. Claiming relative velocity between B and A with B being at rest is not supported by any data once you have accelerated B and demonstrated its time dilation due to motion from acceleration. That change I suggest has nothing directly to do with its relative velocity to A. That is coincidental. It is the acceleration and change in absolute motion that is causing the B clock to have slowed its tick rate and the relative velocity between these clocks has absolutely no impact or affect on clock A. This is the only thing actually supported by emperical data and logic. The rest of your arguements are simply dogma, rhetoric and wrong. Incorrect. All relativity says is that each inertial frame is equal. That from A's view B has the velocity and affects. From B's view A has the velocity and affects. False. Simultaneity only affects perception of when not the actual when. The mathematical formula stands alone and is in the form of t' = t * (1 - v<sup>2</sup>/c<sup>2</sup>),sup>.5</sup> period. This formula stipulates the respective tick rates of clocks, not what time one sees on another clock while in motion or at some remote location. You attempt to mix relavistic issues to mask the reality. Done but not done correctly. Because you are wrong. One does not need to consider, i.e. - a round trip where you have GR affects altering the symmetry of relative inertial velocity. The time dilation formula dictates respective tick rates as a function of relative velocity period. And the reciprocity inherent in SR makes it a false theory.
Then why do you disregard the prelaunch relavistic calculations to take simultaneity into account and to compensate in the timing jof the events in respective frames. Your comments are not applicable here.
Correct. Which is what acceleration and not inertial rest provides. Correct again but note that acceleration has become a fiticious term otherwise you should have a varing EM. My question rasied in this thread has to do with the issue of acceleration where velocity is not constant, you have a varying field and hence a detector comoving with the particle should see the changing EM field. Or a static particle according to relativity is considered to be accelerating if the relative velocity between it and another particle is changing. Even though the particle is undergoing NO F = ma.
It's an extremely definitive answer: No, if the spacetime interval between events (an invariant across frames) is non-zero. Yes, if it is zero. Where? I simply set up a thought experiment to show you, with math, why the rocket would not see the same stop times as the space station. Please point out any errors in the math. But nobody but you uses a concept such as "simultaneity shift". The reason I drag out the Lorentz equations is that you apparently didn't see fit to do the computations yourself. Do you, or do you not, acknowledge that the Lorentz equations have final and only say on the predictions of SR, in this case? If you don't then we're done here. Please define what a simultaneity shift is. And I don't mean a vague description, I want a mathematical description. Well, you can choose an arbitrary reference frame, and define it to be the absolute frame in which events occur "truly" simultaneously. No reason to do that though. Doesn't matter. It is still true. "De facto" simultaneous? No such thing. But it is, of course, possible to calculate if events are simultaneous in one frame or the other. Please use math, and not vague philosophical reasoning. Because, frankly, I don't give a damn about your ideas of how nature ought to behave. I showed that according to SR these two events are simultaneous in the frame of the space station: 1. The space station clock reads 1 hour. 2. The rocket clock reads 30 minutes. And that these two events are simultaneous in the rocket frame: 2. The rocket clock reads 30 minutes. 3. The space station clock reads 15 minutes. If you disagree that this is what SR predicts then show an error in the math. You made statements to the effect that SR gives inconsistent predictions in your scenario - I proved using the actual equations of SR that your expectations of what SR predicts were wrong. Now you're changing the rules to allow you to dictate the outcome of experiments?!? Do you see how insane this is? Here's my counterfact to your "fact": IT IS! Oh, that doesn't convince you? How odd... No, it isn't. It is contra-intuitive, but it is easily explained with the non-transitivity of simultaneity across frames. As Billy T has already described, that arises directly from the isotropic propagation of light. You know, if you were a freshman at the university, or had only just come across this, nobody would fault you for making such a classic mistake. It's the fact that you belabour the point, insisting you're right, when literally millions of physicists have gone through the exact same thing with opposite results that's so annoying. What empirical data? But, as we've also established, that "instant" is tied to the reference frame of A. B doesn't agree: For him those two events are separate in time. I frankly don't see what it matters that he can calculate them to be simultaneous for A. It's a totally arbitrary choice to say that only in one single frame are events simultaneous if you can't somehow (i.e. by experiment) decide which frame it should be. It's just a change of coordinate systems, you lunatic! Absolute motion implies an absolute reference frame. Find it. Now. Or shut up about it. Point to an error in the math, then. Yes, which is exactly what I've stated. Take it to the philosophy section. Do you know how this equation arises? Hint: It has to do with the Lorentz equations. See above. You obviously have no authority to judge that. I'm sorry what? Does this have any relevance to the issues at hand? See, again, you take two things that you think you know what mean, and combine them to form some sort of unspecified contradiction, but when shown the actual math proving you wrong, you can't fault it.
Thank you. It's very useful to think of non-linear worldlines in Minkowski diagrams as the ones with shorter proper time. For instance, it gives us an immediate explanation of how accelerated objects accumulate less proper time (absolutely) than inertial ones: Their worldlines are curved in all inertial frames.
>> Absolute motion implies an absolute reference frame. indeed but absolute depends upon a centre only.... and there is a centre for each spin system in the Universe.... so instead of an absolute frame of reference, call it a preferred frame of reference. When you define systems this way then inertial and non inertial acceleration is clearly identifiable..... because the acceleration is soley referenced by the spin of the system...... it has nothing whatsever to do with any other reference point
Dalespam, I am using just this one of many references, perhaps unfairly, that you posted in order that I make a point. All the historical gedanken using trains and embankments, it is always the train that accelerated, never the embankment. Therefore, only in the accelerated frame does, "time dilation", "frame contraction" and all SRT phenomena occur. This means that the concept of 'the equivalence of inertial frames of reference' has undergone one humungous modification. We can forget about said equivalences in future discussions, may we not asnd aren't the equivalent postulates linked fatally to SRT conclusions and here self-destructively? After all, in order to maintain consistency and symmetry in the scientific models we construct and offer up for consideration and discussion, arbitrariness and mere concensus, brings not even half a sandwich to our scientific picnic do they? Geistkiesel
Are you refering to my comments or to quadraphonic's comments? If you want to argue the specifics of quadraphonic's point then you will have to adress him. My point in posting the above quotes was only that MacM had been responded to in physics and math terms also, and not just "slander". MacM and I have already discussed this point in detail. IMO the relativity argument we were having has been resolved with a partial concensus. I am reluctant to start it over and, as I told MacM, I think it is silly to separate SR from GR and then attack it for not handling accelerating frames. I consider that attack roughly equivalent to complaining that Newton's first law fails in dynamics without considering the more general second law. You may want to try taking up your point with funkstar and MacM who both seem more entertained by this whole discussion. Again, I am sorry. I think there is a little bit of a language barrier. I don't follow your comments. But if you mean to attack relativity as not being self-consistent, then try someone who is not already tired of the argument. -Dale
Well, I think this example shows that it actually takes more than just accelerating charges in order to get radiating photons. In the superconducting loop the individual electrons are traveling in uniform circular motion, so they are continuously undergoing a real centripetal acceleration, not a ficticious acceleration. The reaction forces (on the loop) to the centripetal force (on the electrons) cause some real and measurable stress and strain on the superconducting material itself. So this is not a ficticious term in any interpretation. So given that situation I tried to figure out why one accelerating charge radiates while a bunch of accelerating charges do not radiate. All I could come up with is that even though the individual charges are accelerating the total electromagnetic field is static. I'm sorry, I think I was not very clear in the description of the experimental set up I was considering. I was thinking of a single charged particle that is deflected by going through an external electric field, like in the case of an electron being deflected in a cathode-ray tube. The deflection is an acceleration, the velocity is not constant, and the force is provided by the electric field. My point was that I think that both the inertial rest frame of the external field and the non-inertial rest frame of the electron will agree that there is a changing EM field and therefore both will agree that there should be radiated photons. -Dale
What you "came up with" is of course true, but sort of circular logic or just a restatement that there is no radiating field, don't you not agree? I think a more fundamental view is that each accelerating electron is radiating, but that the sum of their radiation fields is exactly zero. I find this view hard to defend as it is true for any shape of the closed super conducting loop, so how can "net field", Ea, from half section "A" be exactly cancelled net field Eb, when I can bend half section "B" into various different shapes while leaving section "A" geometry unchanged? I did not read this thread earlier but would like someone smarter than me to set us straight, without just restating the fact that the field is static magnetic field. Those electrons are accelerating!
Someone on a different forum said something to the effect that a supercurrent wasn't like a regular current. The electrons are not localized at all in a supercurrent but are smeared out along the whole loop. So they are not accelerating any more than an electron "orbiting" a nucleus is accelerating. My QM is really weak so I just said "wow". However, I am not sure this solves the conundrum, because the same is true for a DC current pushed through a resistive loop of any shape. You get a static magnetic field, but no electric field and no radiation. I don't think that the non-localized electron idea holds there. Personally, I think that it is an indication that Bremstrahlung is just not a fundamental property of accelerating electrons. I don't see how photons from one electron could annialate photons from another one to halt radiation. I just think it is incorrect to say that accelerating charges produce radiation, they do sometimes but not always. -Dale
