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Relativity, time and the speed of light

  1. Jul 10, 2003 #1

    jby

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    It states that nothing can travel faster than light. But all the books that I've read on introduction to relatvity use the train and light pulse to demonstrate length contraction and time dilation. And finally, they say that nothing can travel faster than light. How can this claim be made when they have just only consider light clock. What about mechanical clock, biological clock etc?
     
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  3. Jul 10, 2003 #2

    Hurkyl

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    It all stems from the principle of relativity.

    Even before Einstein, physicists postulated that the laws of physics are the same in all inertial reference frames. (in classical mechanics, we call this Gallilean relativity) This is why you can be in a speeding locomotive, but feel like you're sitting still!

    Then Maxwell came along and collected the most important laws of electromagnetism, including some contributions of his own, into Maxwell's equations. The problem with Maxwell's equations is that they don't work with Gallilean relativity!

    Through the thought experiments with light beams, we see that the needed correction is to allow time dilation and length contraction (I shall now call it Einsteinian relativity). Remember that the governing principle is that the laws of physics are still supposed to be the same in all reference frames.

    The laws of physics include the fact that we can synchronize ordinary clocks (of all kinds) with light clocks... so if Einsteinian relativity is correct, then the time dilation we observed with light clocks must apply to all means of measuring time. A similar argument works with measuring distances.


    This, of course, was very disconcerting to physicists in the earlier part of last century (and even to some in the latter part)... but they have since confirmed the predictions of special relativity in every experiment performed. To my knowledge, there is literally not a single shred of experimental evidence that special relativity is flawed.
     
  4. Jul 10, 2003 #3

    Janus

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    All such clocks must remain synchronized with the light clock that is in the same frame. Otherwise, if you were to bring clocks that have experienced relative velocities back together in the same frame, there would be disagreement as what each clock read. Observer A might say that clock B reads 10:00, but Observer B would insist that it reads 10:10. Remember, this would be after the clocks and observers had been brought back together again.
     
  5. Jul 12, 2003 #4
    Janus' response is only partially right. If the other clock is moved arbitrarily slowly it will show the same time indication when it comes back to the original clock and set to rest in relation to that clock.

    It should be mentioned that there are 2 interpretations of relativity which in all practical situations yield the same results. For Einstein the speed of light c is a constant by itself. In motion the space shrinks and the time is dilated.

    In the other interpretation called the Lorentzian one (which is not the exact original version of Lorentz) the speed of light is *measured* to be the same in all moving frames. Not the space contracts but the physical objects do and not the time is dilated but all physical time measurements. As a result the speed of light c which is *not* the same in different moving frames seems to be the same by measurent.

    As a result in the world of Einstein there is no speed possible greater than c because this is inhibited by our fundamental space properties. In the world of Lorentz the fields and the particles have this speed c as a limit, but it is not fundamentally forbidden that a speed > c can occur. This is an important point in the view of recent experiments which seem to prove speeds much greater that light.
     
  6. Jul 12, 2003 #5

    ahrkron

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    None of those experiments are incompatible with relativity. Information, or any other physical influence, is not transmitted in any of them.
     
  7. Jul 12, 2003 #6
    I know that there are controverse discussions about this point. I have personally observed one of the known experiments (of Guenter Nimtz, Cologne) during which by my understanding information was transfered with a speed much greater than c. This experiment was observed by a lot of physicists who are very critical about it. But none of them could explain all aspects of the experiment without admitting a superluminous signal.
     
  8. Jul 12, 2003 #7
    Please show the source of the information that information is transmitted with a speed much faster than c.
     
  9. Jul 12, 2003 #8

    ahrkron

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    The effect does not pose a problem for SR, and is well understood and explained. No information is transmitted faster than light.

    Imagine a long street, with light posts every 10 meters. You can easily set things so that all of them turn on at the same time: you just have to send the signals at different times (the "turn-on" commands for the farther posts depart earlier, to compensate for the propagation time).

    Similarly, you can also set this up so that the lightning of the bulbs appears to "travel" through the street at, say, 10 times the speed of light.

    The front end of your "bulb-wave" travels faster than light, but no physical influence was transmitted faster than light.

    Nimtz experiment works in an analogous way.
     
  10. Jul 12, 2003 #9
    The Nimtz experiment I have seen works in the following way:

    A microwave pulse of ca. 0.1 ns length is transmitted through air by a distance of 3 meters. Then a specific material which is 3 cm thick is put into the beam. The power of the received pulse is then attenuated by a factor of ca. 400, but the width is the same and there is no signal ribble before or after this pulse. The pulse now arrives ca. 0.1 ns earlier, which means (within the measurement accuracy) that the microwave pulse did not need any time to travel through the material.

    There was an argument that this result can be explained by a frontal wave. That means that only the first little part of the pulse comes through and seems to represent the whole pulse and the rest is extinguished by destructive interference.

    To refute this argument Nimtz has changed his set up. He has transmitted the pulse towards a layer of ca. 0.5 cm thickness where it was reflected towards the receiver. There appeared a pulse of the given length. Then he added another 2.5 cm of this material to the layer. Of course the received pulse amplitude was now increased. But the received pulse was not spread out in time in accordance to the thickness of the reflecting material but it had the same position and the same width. So that one has to conclude that the pulse did not use any time to invade the additional material until it was reflected and also no time for its way back.

    There is a lot of papers of G. Nimtz. One I have at hand is
    A. Enders and G. Nimtz, Photonic-tunneling experiments, Physical Review B, (45,9605) 1993
     
  11. Jul 13, 2003 #10
    I couldn't read the article Albrecht indicated, but I could read the related article of the same author. You are referring to tunneling time. The phenomenon is releted to an evanescent wave. I don' t know details of tunneling time. But can we say the evanescent wave is traveling? I need to know how the light wave travels in the medium from the microscopic point of view.
     
  12. Jul 13, 2003 #11
    I don't know if it was the same person but I saw on either PBS or TLC or Discovery a similar setup in which the throught the medium arrives sooner that the one transmitted through air and he was send a Mozart
    piece over the signal. He said that Mozart should satisfy those who claim that no intelligence could be sent faster that light.
    At the time I assumed he was talking about and demonstrating tunneling.
     
  13. Jul 19, 2003 #12
    Nimtz has in fact transmitted Mozart with a superluminous speed.

    However, whatever the signal transmitted by Nimtz was, an evanescent wave or a tunnelling signal or something different: It was stable enough that it could be used to synchronise clocks in moving systems.

    Normally clocks at different locations and in different moving frames are synchronised in a way that a light like signal (with v=c) is send from one clock to the others. The arrival time of the signal has to be corrected for it's flight time. But because every observer in a different system relates the speed of light c to his own reference system, the result of the synchronisation will look different to the different observers. These differences are symmetric with respect to the systems, so they cannot be used to find that one system is a preferred one. This impossibility fulfils the relativity principle declared by Einstein.

    This, however, changes if a superluminous signal is used. If clocks are now synchronised using on one hand a light like signal (i.e. one moving with c) and using on the other hand a superluminous signal as generated by e.g. Nimtz, both methods will in general have a different result. It can be shown by the Lorentz transformation that there is exactly one inertial system in which both methods have an identical result. So there is a preferred inertial system. And this is in a strong contradiction to the relativity principle of Einstein.

    But it is in no contradiction to the relativity as defined by Lorentz. Lorentz has always stated that there is a preferred inertial system, formerly called the "ether".
     
  14. Jul 20, 2003 #13
    According to my thought, spacetime is regularized by the light. Every textbook of relativity refer to the speed of light in vacuum. If some material which makes a propagating light an evenescent wave intervenes in the path of light, the situation is different from the case in vacuum. We have to discuss the relativity in consideration of the property of the material. Even if the light signal is transmitted faster through the medium, the transmitting time through the medium must be shortest and the speed at that time should be thought like constant (speed of this case may be different from c), I think. We need to know the behavior of an electromagnetic wave in the medium according to the theory of relativity.
     
    Last edited: Jul 20, 2003
  15. Jul 20, 2003 #14
    It is right that the textbooks solely refer to the relativity of Einstein. The relativity of Lorentz which produces equivalent mathematical results is almost completely ignored. As well the logical problems which occur with Einstein but not with Lorentz are ignored.

    The point I made regarding clock synchronisation is independent of how one interprets the cause of the higher speed. It causes anyhow a logical deadlock with Einstein.

    You can also consider the following: If the signal of Nimtz passes the material barrier with a speed greater than c and this is observed from an inertial system which moves with high speed into the opposite direction, the moving observer will see that the signal leaves the material before it has entered it. - This is a very strong logical conflict.
     
  16. Jul 20, 2003 #15
    It's an interesting post but unfortunately not fully accredited as yet. The theory seems to depend on the cascading effect of photons travelling through a medium which would add up to a momentum which is faster than c.
     
    Last edited: Jul 20, 2003
  17. Jul 20, 2003 #16
    On Superluminal Propagation

    For the record, I, would like to point some articles which explain why SUPERLUMINAL TRANSMISSION does not violate Einstein causality (postulate of SR).

    I understand this is a controversial topic among reputable experts, but I share the opinion of these authors (who I happen to know and respect). Another expert who agrees with this interpretation of the results is, of course, Einstein.


    1.
    University of Toronto (currently)
    Prof. Mojahedi - AN ENGINEER

    + Demonstrated superluminal transmission - explicitly mentions that SR is NOT violated.
    + Explains why pulse-reshaping does not constitute faster than c information transmission

    REFERENCE: http://www.grc.nasa.gov/WWW/bpp/pdf/Mojahedi-JPC.pdf
    (see section V - Superluminal Velocities and Einstein Causality)


    2.
    (Quotes from)
    University of Toronto
    Prof. Steinberg - PHYSICIST

    + Refers to Ranfagni's microwave experiment. Explains that this experiment still demonstrates pulse reshaping.

    REFERENCE: http://focus.aps.org/story/v5/st23 [Broken]
     
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  18. Jul 20, 2003 #17
    Quoting Albrecht

    Albrecht said:

    ----
    I know that there are controverse discussions about this point. I have personally observed one of the known experiments (of Guenter Nimtz, Cologne) during which by my understanding information was transfered with a speed much greater than c. This experiment was observed by a lot of physicists who are very critical about it. But none of them could explain all aspects of the experiment without admitting a superluminous signal.
    ----

    Not only physicists are being very critical about it, so are engineers. I personally, am critical about any interpretation that violates causality in its simplist form (effect preceeding the cause). My previous post refers NOT to a 1993 paper, but two articles sharing a more recent, maturing interpretation of superluminal transmission (which is easily reproducable).

    To clarify my point, I am not saying that any researchers "cheated" or that they somehow erred, I am saying that I disagree with the interpretation that violates causality.

    Try plotting (using MAPLE, Mathematica, Origin or whatever) the following curves (if you can't visulalize pulse reshaping) for a demonstration of how pulse reshaping can cause superluminal effects:

    {
    RED: exp[-(t)^2]
    BLACK: exp[-(t-8)^2]
    BLUE: AMP*exp[-(t-8)^2]

    where the amplitude modulation is AMP = {0.7*[arctan(t-7)]^2}

    **Note that I amplitude modulated the blue pulse (just as some mechanism, an UNKNOWN BOX would), but that the Gaussian component is NOT centered at t~9, but at precisely t=8 (just like the BLACK curve).
    }

    Consider the t-axis to represent time. At some earlier time (much earlier - not shown), a Gaussian wavepacket is generated and it is later detected to pass through some detector. This is the RED curve shown. This detector pinpoints the PEAK of the wavepacket to be temporally centered at t=0. The pulse then traverses some distance, goes through some UNKNOWN BOX that reshapes the pulse. The pulse is then directed along some path and returns to the detector.

    The BLACK curve shows what would be detected IF the pulse wasn't amplitude modulated (i.e. wasn't reshaped). Note that it is centered at t=8 (i.e. its PEAK is located at t=8). The blue pulse shows the pulse that was reshaped by the UNKNOWN BOX. Its peak is NOT at t=8, but at t~9. Did this violate causality?

    The point is that although the blue curve travelled at a speed equal to the speed of light, the PEAK of the curve arrived at its destination FASTER than the speed of light. This is OK!
     

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    Last edited: Jul 20, 2003
  19. Jul 20, 2003 #18
    Although I have not read articles sdeliver645 showed and have not conducted calculation sdeliver645 showed, I want to express my opinion.
    I think I understand what sdeliver645 says. Although Albrecht says causality is violated, I believe not so. Yes, what is occuring is pulse reproduction as sdeliver645 says. My problem is how the tunneling time is transformed between inertial frames. As sdeliver645 clearly showed, wave becomes decaying one in the medium in the case of tunneling. So we cannot define phase of decaying wave. We cannot define the speed of decaying wave based on the usual method. If the tunneling occurs at the greater-than-light speed viewed from only one inertial frame, violation of causality occurs. Think that famous diagram which is a sectional view of light cone. But I don't believe causality is violated. Maybe, I speculate that tunneling occurs the same superluminal speed for all inertial frame. If so, I think causality is not violated.
     
    Last edited: Jul 20, 2003
  20. Jul 20, 2003 #19

    ahrkron

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    Great illustration sdeliver645!!

    I'm posting the plot you suggested as an attachment. The light blue curve is AMP(t).

    (the attachment won't show until approved by Greg).
     

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  21. Jul 20, 2003 #20
    Thank you! The attachment clearly shows your understanding! But I have some question.
    1) according to the explanetion attachment shows, time advancement of light pulse should be within half width of original pulse.
    2)further, attenuated pulse's width should be decreased.
    Albrecht's report says:
    1)width of original pulse was 1ns,
    2)width of attenuated pulse was the same as the original one,
    3)advancement of traveling time was 1ns.
    Is Albrecht's report wrong? Or is the explanation not enough?
     
  22. Jul 21, 2003 #21
    I found an article addressed to analysis of this matter. Refer to the article below.
    quant-ph/0011033
    Einstein formulated special theory of relativity by postulating:
    1)relativity
    2)constancy of the speed of light.
    That speed of light should be fastest comes from that values of coordinates should be real numbers. As the above article says, if we accept imaginary number of coordinates, evanescent wave propagation which seems superluminal is also Lorentz covariant. What physical meaning would be assigned to the imaginary coordinate value?
     
  23. Jul 21, 2003 #22
    Trying to Address some Issues

    To try and address some issues:

    The goal of my plot was not to directly address specific issues raised by the '93 article, but to simply graphically demonstrate how it is possible to reshape a pulse (via some amplitude modulating mechanism) so that its peak shifts to a time greater than that of an unattenuated pulse. That is it - its value lies in this alone.

    Thus, one of shchr's comments which addresses specific number values (which, as per the nature of the experiment are on the order of nanoseconds - i.e. FWHM of pulse being 1ns) isn't relevant. My demonstration wasn't put forth to address these specific issues. It is just a demonstration.

    shchr wrote:

    1) "...time advancement of light pulse should be within half width of original pulse."

    - This is the case. You can see that (in attachment c1.gif) the blue pulse is entirely enclosed within the black pulse, and further that it is ever so slightly shifted to the right, thus is well within the FWHM of the black pulse.

    2) "..attenuated pulse's width should be decreased."

    - It clearly is. The blue pulse has a max. amp. of ~0.6 whereas the black pulse has a max. amp. of unity.


    -----
    Also, Einstein's two postulates of SR are put most sucinctly as:

    a) All inertial frames are equal (equivalence).
    b) The speed of light in are inertial frames of reference is the same.

    That's it. So, (not to address this to anyone specifically), when impugning SR, attack either (a) or (b).

    P.S. Good luck (not a sarcastic remark). If you find a flaw in (a) or (b), and your claim has merit, NOBODY will make fun of you. I am sure you will find ample support (not to mention commercial endorsements from Nike and the Swedish Academy of Sciences).
     
  24. Jul 22, 2003 #23
    Since I find here so much speculation about what the experiment of Nimtz is/was I shall give some more details. This experiment was demonstrated during a congress in 2002, I do not know a paper which describes it in exactly this variant.


    Fist of all: I did use myself all the arguments I read in the preceding threats before I could see the experiment with my eyes. It took me one day to accept what I have seen.

    The pulse width was not 1 ns but 0.1 ns corresponding to a photon's travelling way of 3 cm. And this also was the width of the barrier in the first experiment. The time advance was ca. 0.1 ns, so the full width of the pulse, not half of it. The advanced pulse is attenuated by ca. a factor of 400. See the attachment (upper part) which is not to scale. If this is really reshaping which is principally possible then it should be understandable how this works in detail. The only explanation I can imagine is that most of this pulse is extinguished by destructive interference. I have problems to believe that this is possible to the extent demonstrated here.

    The second case (see the attachment, lower part)) is a reflection process. The pulse is first reflected by a thin layer, ca. 0.5 cm thick (blue pulse). It arrives at it's original width. Then another layer of the same material is added to the layer, so now the whole layer is 3 cm thick. Now the received pulse is amplified (red pulse) which is of no surprise. But the surprise is that the pulse width is not extended as it should be (dashed line) due to the different path lengths in the material before the pulse is reflected somewhere. It has in the contrary the same width. I would wonder if anybody would be able or willing to explain this by pulse reshaping.

    A true superluminous signal speed causes in fact a violation of causality if we believe the theory of Einstein. An observer in an inertial system moving opposite to the signal at sufficiently high speed will find that this signal arrives at the receiver before it has left the transmitter. Such thing cannot happen. And it will not happen if we follow Lorentz rather than Einstein.

    I meant this example of superluminous transmission as only one of several examples for problems with the Einsteinian interpretation of special relativity. There are more of it. E.g. the twin paradox. In the gedanken experiment please consider the time progress of the astronaut who turns back towards earth. Due to the Einsteinian formalism he can have a time progress of several years in the moment (maybe a few hours) when he turns back. But the clock which he may carry with him will on the other hand show a 'normal' time progress.

    There is a similar problem with a specific kind of the Thomas precession which is really a logical deadlock. It is too complicated to be explained now here but I plan to post it into the web.

    To come back to the question/statement of sdeliver645:

    a) All inertial frames are equal (equivalence).
    b) The speed of light in are inertial frames of reference is the same

    It is easy to attack both if we follow Lorentz:

    a) There is exactly one preferred inertial frame (i.e. absolutely at rest)
    b) The speed of light is in general different in different inertial frames. However if we measure the speed of light we will get the same result in all inertial frames. This comes from the two relativistic phenomena: The contraction (of our length gauge) and the dilation (of our clock which also has the effect that clocks at different positions have a different time indication which is not visible to somebody in the same inertial frame)

    In general: The Lorentz interpretation of special relativity is in practice equivalent to the Einsteinian interpretation, i.e. it yields the same mathematical results. But it is mostly ignored by the physical community by reasons somebody else must explain.

    Note: what I call here the Lorentzian interpretation is not the original statement of Lorentz but the improved definition used nowadays
     

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    Last edited: Jul 22, 2003
  25. Jul 22, 2003 #24
    <- Albrecht said ->
    "..There is exactly one preferred inertial frame (i.e. absolutely at rest)"

    COMMENT: Before you comment on the rest of the feedback I provide in this message, PLEASE show us an article that experimentally shows that there is a preferred inertial frame in the universe. This is critical to your reputation because the statement is indeed very controversial.

    <- Albrecht said ->
    "...several examples for problems with the Einsteinian interpretation of special relativity. There are more of it. E.g. the twin paradox"

    There are two errors you have made in the above statement ALONE. The first is only a matter of terminology, but the second is a poor analysis of the problem.

    1/ There is no other interpretation of "special relativity". The term "special relativity" was coined by Einstein and is nothing more than the Lorentz transformations (which are a result of his two postulates). As many other people will concede, Einstein's two postulates (alone) are used to derive the Lorentz transformations. The derivations are entirely algebraic and are done in a first- or second-year physics course.

    2/ The "twin paradox" is not a paradox for special relativity, and as such is not a "problem" for it (as you say it is). Here is a link to a proper (accepted) analysis:

    http://www.phys.unsw.edu.au/~jw/twin.html

    Please don't continue posting incorrect information; it will confuse (and mislead) those who are not properly informed.

    I have decided to include some references to very recent articles with other experiments (there are quite a few of them) which demonstrate superluminal pulse propagation.
    They ALL demonstrate superluminal* propagation while maintaining causality and are 2003 publications.
    If you would like to challenge the authors, it is only fair to e-mail them (and their institution) with your objection.

    * "superluminal" according to the currently accepted definition

    Search the website http://prola.aps.org/search to see where I obtained these references:
    V. Petrillo, et al., Phys. Rev. A 67, 012110 (2003)
    ...Some of the characteristic times of tunneling are calculated and compared; they are all of the same order of magnitude and all indicate an apparent superluminal motion, even if causality is maintained...

    S. L. Konsek, et al., Phys. Rev. B 67, 045306 (2003)
    ...Tunneling transport is shown to be causal, and no evidence of superluminal behavior is seen, either for resonant or for off-resonant tunneling...

    H. G. Winfil, et al., Phys. Rev. Lett. 90, 023901 (2003)
    ...The theory presented here provides a physical explanation of the tunneling process and resolves the mystery of apparent superluminality....

    D. Rohrlich, et al., Phys. Rev. A 66, 042102 (2002)
    ...We discuss the consistency of weak values and show that superluminal weak speed is consistent with relativistic causality....

    D. Solli, et al., Phys. Rev. E 66, 056601 (2002)
    ...The causality principle does not forbid negative group delays of analytic signals in electronic circuits; in particular, the peak of a pulse can leave the exit port of a circuit before it enters the input port...
    ...Furthermore, pulse distortion for these "superluminal" analytic signals can be negligible in both the optical and electronic domains...

    Regarding the twin paradox:

    The Hafele and Keating Experiment
    ------------------------------------

    (a proof of time dilation)

    Ref: J.C. Hafele and R. E. Keating, Science 177, 166 (1972)

    Quote from Science article:

    "During October, 1971, four cesium atomic beam clocks were flown on regularly scheduled commercial jet flights around the world twice, once eastward and once westward, to test Einstein's theory of relativity with macroscopic clocks. From the actual flight paths of each trip, the theory predicted that the flyng clocks, compared with reference clocks at the U.S. Naval Observatory, should have lost 40+/-23 nanoseconds during the eastward trip and should have gained 275+/-21 nanoseconds during the westward trip ... Relative to the atomic time scale of the U.S. Naval Observatory, the flying clocks lost 59+/-10 nanoseconds during the eastward trip and gained 273+/-7 nanosecond during the westward trip, where the errors are the corresponding standard deviations. These results provide an unambiguous empirical resolution of the famous clock "paradox" with macroscopic clocks"
     
    Last edited: Jul 22, 2003
  26. Jul 23, 2003 #25
    Right, the term "relativity" was invented by Einstein. Does he have a trademark on it? May we agree to use this term for the whole physical context?

    What we have for sure are the relativistic phenomena: time dilation and contraction. They do exist independent of any theory. When the Michelson experiment had to be explained there were several physicists who gave a possible explanation for it. If the fact of contraction is used (Lorentz, Heaviside, Lodge, Fitzgerald, and Lamor) Michelson is explained; but others added the fact of time dilation to the theory (Einstein, Lamor) which is of course necessary. Later relativity was identified with the name of Einstein only. The main difference of the working versions of relativity is whether a specific frame at rest is assumed (Lorentz) or not (Einstein). Both versions work mathematically equally and correctly in the normal context. Lorentz unfortunately did not accept time dilation into his theory but this was added later to the version with his name. That is what I am referring to.

    For the historical development of that early stage of relativity I refer to the very recommendable paper of Prokhovnik. It is easily readable and gives a good survey:

    Prokhovnik, S. I., The Physical Interpretation of Special Relativity - a Vindication of Hendrik Lorentz. Z. Naturforschung 48a, 925 (1993).

    Even if it needs effort to get it, please do it, it is worth to be read.

    This point depends entirely on the existence of experiments with true superluminous transmission. I am convinced to 90% of the experiment of Nimtz but I am in discussion with him whether it can be refined.

    If there is a real superluminous signal transmission there is nothing more necessary than the application of the Lorentz transformation to show the logical conflict. If you take the time portion of the L.T. and have a time difference (t0-t1) at different points which is shorter than possible by a light like signal then it is straight forward to find an observer-speed v for which the transformed time difference (t'0-t'1) is negative, so you have a time reversion which is logically not possible. This proves directly that the inertial frame with v is not equivalent to all others.

    An example for the reversed time: You shoot a projectile by a gun with superluminous speed. For an observer with a sufficient speed the following happens: The projectile hits the target before it has left the gun tube. (This example was once created by the philosopher Bertrand Russel).

    You can find some papers about this published by the well known Italian quantum theorist Franco Selleri who has committed himself to the Lorentzian Interpretation. He has presented what I have explained above on conferences, I do not know a specific paper of him. But Selleri has a home page in the web with a huge number of publications, there will be something about this topic. - So again, if you want some person with reputation for these statements I believe Franco Selleri is one.

    I have read the site earlier and now again.

    1st version: When Jane turns around, Joe all of a sudden ages. Why should he? And if Jane turns around after twice the time he ages twice that amount. Maybe he has definitely lost the contact to her, why should he age all of a sudden? And now assume that there is besides Jane also Mary on travel in the universe in a different ship. At some different time Mary will turn around. Will now Joe age in accordance to Jane or in accordance to Mary?

    You see, this is not at all a physical process but only the presentation of a mathematical construct in pictures. The version of Lorentz does not have the need to do such things.

    The alternative version:
    Jane can turn around (by physical means) with arbitrarily high acceleration. (If her body is not able to withstand this we can replace Jane by a shock-proof clock.) Then the turn-around may be finished after an hour or after a day, doesn't matter. Even if her time progress stops completely during this time she has only gained 1 day compared to Joe. Now the ageing difference of 2 years has entirely to happen in the body of Joe in a very short time. Causing the some question as above.

    I have once read an earlier version of this web site and at that time the author has stated that the sudden ageing of Joe has no physical meaning. Well, I see, he has deleted that statement.

    So, thank you for this example, it shows quite well what I mean. All these problems do not occur if Lorentz is used. Then the same process can even be understood by medium class school kids. Sorry to say this.

    I have explicitly said that time dilation exists. (Sorry, I have to ask to read my threat carefully). Regarding the Hafele and Keating experiment there is in fact no difference between the Einsteinian and the Lorentzian interpretation of relativity. Again, I have never objected against time dilation.
     
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