Relativity, time and the speed of light

[jby]

It states that nothing can travel faster than light. But all the books that I've read on introduction to relativity 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?

 

[Hurkyl]

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.

 

[Janus]

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.

 

[Albrecht]

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.

 

[ahrkron]

Originally posted by Albrecht
This is an important point in the view of recent experiments which seem to prove speeds much greater that light.

None of those experiments are incompatible with relativity. Information, or any other physical influence, is not transmitted in any of them.

 

[Albrecht]

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 transferred 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.

 

[shchr]

Please show the source of the information that information is transmitted with a speed much faster than c.

 

[ahrkron]

Originally posted by Albrecht
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.

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.

 

[Albrecht]

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

 

[shchr]

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.

 

[Royce]

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.

 

[Albrecht]

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".

 

[shchr]

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.

 

[Albrecht]

According to my thought, spacetime is regularized by the light. Every textbook of relativity refer to the speed of light in vacuum.

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.

 

[McQueen]

Originally posted by Albrecht
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.

It's an interesting post but unfortunately not fully accredited as yet. The theory seems to depend on the cascading effect of photons traveling through a medium which would add up to a momentum which is faster than c.

 

[sdeliver645]

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

 

[sdeliver645]

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 transferred 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 traveled 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!

 

[shchr]

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 occurring 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.

 

[ahrkron]

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).

 

[shchr]

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?

 

[shchr]

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?

 

[sdeliver645]

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).

 

[Albrecht]

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 traveling 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

 

[sdeliver645]

<- 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"

 

[Albrecht]

sdeliver645 wrote:
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).

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.

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.

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.

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

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 website 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.

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)

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.

 

[sdeliver645]

I purposely placed my first question AT THE TOP of my last response. You side-stepped the issue. Please address it:

---from last post---
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.
--------------------

I am currently writing an e-mail to Prof. Selleri to clarify these issues. I will post the correspondence when I get a response.

The PROLA has has cited Prof. Selleri 8 times, yet they don't seem to address the issues you mentioned.

 

[Albrecht]

I am currently writing an e-mail to Prof. Selleri to clarify these issues. I will post the correspondence when I get a response.

That is a great idea.

There is a book of Franco Selleri:

F. Selleri et al., Die Einsteinsche und lorentzianische Interpretation der speziellen und allgemeinen Relativitätstheorie. Karlsbad:VRI 1998.

This book is unfortunately only available in German. It explaines very much in detail the equivalence of both interpretations.

For an English reader my recommendation is still to read the paper of Prokhovnik which is a very short elaboration of the topic.

At the PIRT conference in London in 2002 about relativity Selleri has given a contribution with the title:

"SUPERLUMINAL SIGNALS REQUIRE A MODIFIED THEORY
OF RELATIVITY"
where he stated that superluminal signals are not compatible with the relativity of Einstein.

At the same conference I have given a talk showing that special relativity (Lorentz) can be derived from our understanding of particle physics without any need of Einstein's assumptions about space and time.

 

[sdeliver645]

This is the third time I am asking:

PLEASE show us an article that experimentally shows that there is a preferred inertial frame in the universe.

 

[shchr]

I found this.
physics/0104063
Even if Lorentz symmetry would be violated, there would remain Galilean relativity. So I can't believe there is a preferential inertial frame.

 

[sdeliver645]

shchr:

I am currently debating with Albrecht who has made some outrageous claims. You are absolutely right, there indeed is not preferred inertial frame in the universe. People like Albrecht simply make these bold claims and put the onus on the SCIENTIST to refute the claim. As any reasonable thinker will tell you, it is in the spirit of the scientific method that the onus is on the opposer of the currently accepted theory. Albrecht hasn't proved a thing...

I am currently wasting my time refuting claims that Albrecht has made. This has required me to contact the source of his claims. Here is what Albrecht said regarding a website that demonstrates that the Twin Paradox is not problematic for special relativity:

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

<Albrecht>:
"...I have once read an earlier version of this website 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."

Well, I contacted Prof. Wolfe who created and maintained the site, and here is his response:

<Prof. Wolfe>:
"...I don't think that I have changed the text of the website since putting it up, (although I did add some links in May this year, which is the date of posting, and I added the animation a year or two ago).

I am absolutely certain that it never contained a mention of "the sudden aging of Joe has no physical meaning". I have no idea what "sudden aging" might mean in this context.

Best
Joe"

Although I am still waiting for a reply from an Italian professor whom Albrecht claims is an opponent of SR (he very well may be), please don't do as I have done as WASTE YOUR TIME REFUTING CLAIMS BY PSEUDO-SCIENTISTS. I highly doubt that Prof. Selleri will concur with all the statements made by Albrecht, especially that of there being a preferred inertial frame "that of being ABSOLUTELY at rest". What an empty statement...as if the word ABSOLUTELY adds anything to its worth.

I began pursuing Albrecht's controversial claims, and my responses were met with even more outrageous claims.

I have never been shown any peer-reviewed publications (i.e. Nature, Science, Physical Reviews, etc.) that demonstrate any "holes" in special relativity.

Albrecht, I have enjoyed sparring with you, however this charade must come to an end. Good luck with violating causality, and I pity those whom you are able to convince.

 

[shchr]

I checked above site, sdeliver645.
This site describes what I read in relativity books. I am totally convinced by the explanation. We need to consider the effect of General relativity when we solve the twin paradox. Don't consider only Special relativity. This paradox includes non-inertial frame.

 

[sdeliver645]

shchr:

You are precisely right. The "paradox" arises when applying a non-inertial frame to SR.

The treatment on the web is the one, and only, correct interpretation. It was what I learned in school also...

Thanks for your support!

 

[Albrecht]

sdeliver645 wrote

This is the third time I am asking:

PLEASE show us an article that experimentally shows that there is a preferred inertial frame in the universe.

Sorry, sdeliver645, I have meant my last threat as a response to this. I want to satisfy you and do it now differently.

First: There is not one article as this is normally a 2-step-process

1. An experiment
2. The theoretical evaluation of it.
(Sometimes the other way around)

Example:
1. The experiment of Michelson
2. The theoretical evaluation of Lorentz/Einstein
Both together showing relativity.

In this case

1. The experiment of Nimtz (as an example). It is published several times, I gave the reference for one case earlier.
2. For the theoretical evaluation I have a paper of Franco Selleri which shows that experiments of this type prove the existence of an absolute system at rest.

This paper was distributed by Selleri at the mentioned conference about relativity. It is unpublished. I give you the following link to the conference program:
http://osiris.sunderland.ac.uk/webe...ical Interpretations of Relativity Theory.htm

This paper should better be published, true! And here is a problem I hope I can make you sensitive for. It seems that papers of this kind cannot be published at present. Selleri has shown me at a previous time a very interesting paper which also treated the problem of a possible absolute space. He said that he does not see a chance publish it. It seems to be a rule that papers with discussions about special relativity are rejected by the physical journals. - Question: why? Would you believe that Selleri does not have the intellectual capability to understand relativity? I guess, not. So, why is it as it is?

Anyway, if you want the mentioned paper of Selleri I shall send you a copy.


Regarding the *twin site*: http://www.phys.unsw.edu.au/~jw/twin.html

Please look to the right hand diagram which shows the time flow as seen from Jane's system: There is a time scale for Joe's world points (time and range) at it's left edge where it has 4 equally spaced intervals. The labels are: Joe 1, --- , Joe 7, Joe 8, the numbers mean the years of Joe. There is an obvious time jump at "---" (i.e. the time when Jane goes around) of 4 years in an instant! This was what I meant by sudden ageing.

Of course Joe will not age by 4 years all of a sudden. And if Jane receives permanently time coded signals from Joe there will not be such a sudden time jump in these signals. The thing that happens is that the frequency of these signals increases as a consequence of her turn but nothing drastic.

But if you make use of the normal Lorentz transformation you will indeed get what this diagram shows.
in t' = gamma* (t - v*x/c^2)
t' has a sudden change at sign inversion of v which can be huge if x is huge.)


Alternatively you can use an equation given in Landau & Lifschitz, "Classical Field Theory": §3:

dt' = dt* SQRT(1-v^2/c^2)

This is the differential version of the Lorentz-time transformation. Is is simple to use and free of any paradoxes. You have to apply it to the motion of Jane and of Joe and whoever will be involved. You get the correct result in the easy way.

Even though it was clearly not the intention of Landau & Lifschitz to present the Lorentzian relativity this conforms to the modern Lorentzian way.

Now I will be wondering whether somebody of you has an objection against the use of this equation.


I read that Prof. Wolfe denies to have changed the text. I have made a copy of the statement in the previous version (ca. 15 months ago) which is unfortunately at a different location. As soon as I can get it I will post it here.

If Prof. Wolfe does not understand what I mean by sudden ageing he should look to his right hand diagram. That is it!

So again, sdeliver, I always answer to your concerns, please also respond to my answers. And please read carefully. I never said that causality is violated. It is in fact not. I have shown that a superluminal signal in connection with the relativity principle can cause situations where causality would be violated. That means only that superluminal signals and the relativity principle cannot be true at the same time. And that is exactly what also Selleri says.

shchr wrote:

We need to consider the effect of General relativity when we solve the twin paradox. Don't consider only Special relativity. This paradox includes non-inertial frame.

You are right and it is great that you mention it. This is in fact overlooked or denied by most textbooks I know. Even P. French, "Special Relativity" makes a wrong statement.

But this is only a minor correction to the ageing calculation, the possible existence of logical problems does not depend on it. Take a practical example. Jane may save an amount of ageing of 2 years. Her turn-around may take 1 week. Even if her internal time progress stops completely during this time due to the GR effect this is only a marginal contribution.


And at the end: Even if many of you cannot follow me that the relativity of Einstein has logical problems I believe that it would be a great progress if physicists would understand that the way of Einstein is at its best only one of several possible ways of relativity. Again I encourage you to read the paper of Prokhovnik:

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

 

[shchr]

Albrecht:
Jane's time advance becomes appropriate time so that the paradox is resolved. This number is not the arbitrarily fittable one. Jane changes her frame at the turning point. So there are 2 different frames before and after the turning point for her. In order for Jane to change between those frames, time advence of her must be correct one so that the paradox is resolved. It does not depend on how long she takes to change frame seeing from Joe. You said that let's make the time advance 2 years. This is incorrect. We cannot set the time advancement arbitrarily. The time advancement is determined by what frames she is on. 2 frames are related by her acceleration. Her acceleration is connected to effect of gravity. Gravity governs time advancement.

 

[Hurkyl]

Special relativity is perfectly capable of handling the "twin paradox" without having to resort to GR. The only reason there is a paradox is because people try to apply unchanged the equations of physics in the accelerated frame. If you modify the equations to account for acceleration, SR is perfectly fine at handling non-inertial reference frames, just like you can use Newtonian mechanics in accelerated frames; things like centrifugal forces get introduced... though in SR we also get odd temporal effects (e.g. time runs backwards at distant places away from which we are accelerating)

 

[shchr]

Can special relativity describe a proper time of non-inertial frame?
PS. I seem to have made a mistake in the last post. Jane's time advanse seems to depend on how long she takes to change two frames seeing from Joe as well as what value the acceleration takes.

 

[Hurkyl]

By using an inertial frame of reference, one can use the differential formula:

(c d&tau;)² = (c dt)² - dx² - dy² - dz²

to compute proper times along an accelerating worldline.

Similarly, one uses basic differential geometry to construct, in the inertial frame the proper coordinate axes for the accelerating worldline at each point.

Then, we can align the coordinate axes to form a rectilinear system. (Though we typically have the problem that distant events appear multiple times in the new system)

That is how we can use special relativity to construct the physics of an accelerating frame. The work involved in doing such is, of course, very similar to what one would do in General Relativity (but in GR reference frames would be limited to be local things)

 

[shchr]

For everyone who are interested in uniform acceleration in relativity.
aether.lbl.gov/www/classes/p139/homework/eight.pdf

 

[Albrecht]

Hurkyl and shchr
thank you for the answers.

Regarding the twin paradox

By my understanding the acceleration of Jane has generally to be taken into account. If we believe in the equivalence of acceleration and gravitation then acceleration will make it's own contribution. - However the time difference between the frames depends stationary on the frames and should be independent from the specifics of the acceleration. If Jane changes into the new frame this new frame will not "know" what the history of Jane was.

On the other hand we should in the gedanken experiment be able to eliminate this contribution. If we assume the Jane does not make a normal turn-around but jumps into another spaceship which comes with the same speed from the opposite direction then we can reduce the acceleration time to almost 0. (Jane's body will not be able to withstand this but for the understanding of the relativity process this does not matter.)

This is for my understanding in agreement to the website linked by shchr:
aether.lbl.gov/www/classes/p139/homework/eight.pdf

It is right that the normal Lorentz transformation yields the correct result for the final state, when Jane meets Joe again. But in the meantime we have a situation which looks physically not very logical.

The intermediate problem comes from the requirement of symmetry between all inertial frames (Einstein). We can first look to it in the naive way. When, as in the given example, Jane flies away 3 years (Jane's time) she has to regard her own frame as the frame at rest, so she has, knowing relativity, to assume that Joe's ageing is dilated. Also when she flies back she again will regard her own frame as the frame at rest and assume that Joe's ageing is again dilated. So when she comes back and meets Joe she will expect that Joe is now 2 years younger than she is (taking also into account the contraction of the travel distance). But she would now see that he is in fact 2 years older than she is.

This logical problem is (formally) resolved in the relativity of Einstein by the fact/statement that Jane changes her reference frame at her turn around and that at this moment she has to adapt to the new time.

The physical conflict with this formal way is clearly visible if during the whole travel Joe transmits time-coded signals towards Jane, say one per second like the GPS satellites do it. At her first leg she will receive these signals at a reduced rate due to the Doppler effect on one hand and at an increased rate due to her own dilated time measurement. Both effects compensate to a certain degree. When she turns around she will now receive an increased rate of the signals from the Doppler effect as well as from her dilated time measurement. But all the time she will receive these signals in the correct sequence! No signal will be lost or has an inverted time sequence.

If Jane knows the Lorentz transformation (Einstein), she knows that she is in a different reference frame after her turn around and she has to adapt her time to the time of the new frame in a big step. - But when she looks to the time signals coming from Joe she will not find it logical to do so.

Whatever Jane does with her clock setting, the increased signal rate which she receives during her return will give her a continuous information of an increased ageing process at the location of Joe relative to her. And when she now meets him again, there is not at all a surprise that he has aged more than she did.

The whole process is on the other hand very simple and free of sudden time adaptations, i.e. Jane's clock time behaves continuous to her signal reception, if Lorentz rather than Einstein is used. I shall explain it in 2 steps:

1. Assume that Joe is in the absolute frame at rest. Then Jane has nothing to do than to use the differential Lorentz version
dt' = dt * SQRT(1-v^2/c^2)
to correct permanently her own time indications in relation to Joe's time. She has to do it on both legs and on return she will have the correct time relation between herself and Joe
2. Assume that Joe is not in the absolute frame at rest. Then Joe as well as Jane have to make the time corrections as given above according to their individual speeds in relation to the absolute frame at rest. - This works for every assumed absolute frame at rest.

The result of case 2 will be the same as in case 1, and both results will be correct. And you may see that this is a simple logic without any logical conflicts and without any sudden time changes.

The basic difference between the way of Lorentz in relation to the way of Einstein is that, following Lorentz, Jane cannot assume that both legs of her travel are equivalent frames at rest.

 

[shchr]

Albrecht:
It is very difficult for me to analyze your assertion. Let it simple. In the case 2 above, i.e., Joe is not at rest, what happens when Jane observes Joe? Conversely, what happens when Joe observes Jane?

 

[Albrecht]

shchr wrote:

It is very difficult for me to analyze your assertion. Let it simple. In the case 2 above, i.e., Joe is not at rest, what happens when
Jane observes Joe? Conversely, what happens when Joe observes Jane?

My preceding posting regarding the twin paradox had 2 parts:
1. I have tried to explain why Einstein yields the correct result but is physically difficult
2. I have tried to explain that also Lorentz yields the correct result and is physically easy.

I understand you refer to part 2.

If Joe is at rest and he observes Jane he will see that her clock proceeds with a reduced speed in relation to his clock. Her motion is in no respect special, she moves at her specific speed outbound and then at the same speed back to him.

If now Joe is not at rest but moves with speed v0 in relation to the frame at rest towards Jane, then Jane does in fact not move with v as Joe believes but with v0+v (later v0-v). Now the clock of Jane proceeds even slower than assumed above. But also the clock of Joe proceeds slower than if he would be at rest. Also the distance from Joe to Jane is reduced due to contraction which is however only noticeable by an observer at rest. These effects altogether compensate each other and cause that Joe will make exactly the same observations as in the case when he is at rest.

If Joe is at rest and Jane observes Joe she will observe, if she receives time coded signals from him, that these signals arrive at a reduced rate. If she is aware of her motion she will understand why the rate is reduced in the way I described in my preceding posting. On her way back she receives the signals at an increased rate (and will in the summary come to the conclusion that Joe ages faster than she does).

If she is not aware of her motion when she moves away, i.e. she believes that she is at rest now, she will have the impression that Joe ages more slowly than she does. But when she turns around then she has in this case to be aware of the fact that she is now at a very high speed (twice of the speed assumed above) and now when observing the time coded signals, she will come to the conclusion that Joe ages very rapidly. This rapid ageing will overcompensate the reduced ageing of Joe which she observed on her first leg of motion.

If now again Joe is not at rest and Jane moves correspondingly at a different speed (in relation to the frame at rest) on her travel away from Joe and later towards him, the effects of her different speed and of the speed of Joe and also of the contraction will again compensate each other for every phase of her travel and cause that she will not notice the change. So Jane's observations are exactly the same as if Joe would be at rest.

This is the observation. I this understandable?

 

[shchr]

If now Joe is not at rest but moves with speed v0 in relation to the frame at rest towards Jane, then Jane does in fact not move with v as Joe believes but with v0+v (later v0-v). Now the clock of Jane proceeds even slower than assumed above. But also the clock of Joe proceeds slower than if he would be at rest. Also the distance from Joe to Jane is reduced due to contraction which is however only noticeable by an observer at rest. These effects altogether compensate each other and cause that Joe will make exactly the same observations as in the case when he is at rest.

If now again Joe is not at rest and Jane moves correspondingly at a different speed (in relation to the frame at rest) on her travel away from Joe and later towards him, the effects of her different speed and of the speed of Joe and also of the contraction will again compensate each other for every phase of her travel and cause that she will not notice the change. So Jane's observations are exactly the same as if Joe would be at rest.

Why is Joe specific? Both Joe and Jane are moving with respect to the rest frame.

 

[wimms]

Acceleration is manipulation of timeflow rate. Inertial frame has unchanging timeflow rate, dependant on v relative to point of departure.

 

[Albrecht]

shchr wrote:

Why is Joe specific? Both Joe and Jane are moving with respect to the rest frame.

Joe is specific because he is all the time in the same inertial frame. This frame may be assumed to be the absolute frame at rest .

Jane on the other hand can only be in the absolute frame at rest in one of both legs of motion as she undergoes an acceleration.

Whether the situation of Joe is in fact the absolute frame at rest or not does not change the result. The effects of his motion to the clock speed of Joe and to the clock speed of Jane together with the effect of contraction compensate each other to an extent that it does not matter for the result whether he moves or not. Jane is different because she cannot be in the frame at rest all the time and the compensation does not work.

You find this process of compensation described and mathematically proven in all textbooks about the relativity of Einstein. The authors show and prove how it works in detail that, if you observe a physical situation from a different frame, you will have the same relation between the physical quantities time, length and velocity as in the original one. Please look to the chapters about addition of velocities and about synchronisation of clocks.

wimms wrote:

Acceleration is manipulation of timeflow rate. Inertial frame has unchanging timeflow rate, dependant on v relative to point of departure.

I believe that the timeflow rate is in fact the clock rate, i.e. the circulation frequency of all periodic processes. It is right that there is no change of the rate if there is no acceleration. But the rate also depends on the velocity of the frame (according to the Lorentzian version).

 

[shchr]

Joe is specific because he is all the time in the same inertial frame. This frame may be assumed to be the absolute frame at rest .

So, all inertial frames are assumed to be the absolutely-at-rest frame, aren't they? This means that there is no absolutely-at-rest frame, doesn't it? It is contrary to your previous assertion, i.e., there is a frame which is absolutely at rest.
Does anyone have an opinion?

 

[Albrecht]

This means that there is no absolutely-at-rest frame, doesn't it?It is contrary to your previous assertion, i.e., there is a frame which is absolutely at rest.

This is definitely wrong. Please read again my previous posting.

There is exactly one absolute frame at rest. However, if somebody is in another inertial frame and performes experiments, then the measurement results, which deviate from the ones made in the absolute system at rest, cause compensations to each other so that the experimenter will not see any difference.

Example (simplest possible): If Mike and Mary are in a frame which is not the frame at rest. They have both dilated times indicated on their respective clocks. If they now compare their clocks they will not see any deviation to each other.

 

[wimms]

Originally posted by Albrecht
I believe that the timeflow rate is in fact the clock rate, i.e. the circulation frequency of all periodic processes. It is right that there is no change of the rate if there is no acceleration. But the rate also depends on the velocity of the frame (according to the Lorentzian version).

Why is 'clock rate' more correct?
How I understand it is that time/clock rate is really independant of anything external. When Jane starts off from earth, she initially has same rate as earth. During acceleration, rate changes relative to earth. When acceleration stops, rate that was achieved is sustained until deceleration starts, and is convertible to Earth's rate via lorentz.

What puzzles me, is there really any chance to determine time rate of approaching relativistic body, if it has never been in same rate frame as us. We can transform rate by knowing its v, but is the result we'd get credible? What if the departure frame of this body had different rate than we have? Do we have to assume that there exists universal time rate depending on v relative to universal absolute rest frame?

 

[shchr]

However, if somebody is in another inertial frame and performes experiments, then the measurement results, which deviate from the ones made in the absolute system at rest, cause compensations to each other so that the experimenter will not see any difference.

So, an experimenter cannot determine which is the absolutely-at-rest frame. This means there is no way to know what inertial frame is absolutely-at-rest physically. From physical point of view, it is equal to the fact that there is no absolutely-at-rest frame. For me, your absolutely-at-rest frame is arbitrarily selected from among inertial frames. Which inertial frame is absolutely at rest seems to be the problem of belief, because there is no way of knowing the absolute rest.

 

[Albrecht]

shchr wrote:

Which inertial frame is absolutely at rest seems to be the problem of belief, because there is no way of knowing the absolute rest.

This is correct. Up to now we were not able to find the absolute frame at rest. I wrote it already several times in my preceding postings. So it is a belief. (Unless we have true superluminal signals; then we know it.)

On the other hand, the assumption of Einstein that time and space change at motion is also a belief as it is not necessary.

So we have the choice:

Either we believe that there is a frame at absolute rest. Then we can maintain our traditional understanding of space and time.

Or we believe that every inertial frame is truly equivalent to each other. But then we have to accept the complicated assumptions of Einstein about time and space.

The historical reason why Einstein liked his version and why many years(!) later the physical community accepted it, was the cultural background of this decision. It was understood as intellectually clean and "beautiful" (Einstein) that the assumption of a frame at absolute rest (called ether) could be omitted. This had to do with the intellectual tradition in Germany: Everything was taken as valuable that could be related to Greek philosophy. It does not fit very well to the world-structure ideas of Plato that there exits an ether.

But is this really a physical argument?

wimms:
Sorry, I shall answer your comment by tomorrow.

 

[shchr]

This is correct. Up to now we were not able to find the absolute frame at rest. I wrote it already several times in my preceding postings. So it is a belief. (Unless we have true superluminal signals; then we know it.)

Thank you, Albrecht, for talking with me.
If we discuss further, it would go to a place no one can decide which is correct. So I suggest to stop talking about the existence of absolutely-at-rest frame.
Anyway, Nimtz's experiment was interesting one. Thank you for your information. But I want to remind you the existence of Galilean relativity in which infinite speed is allowed, at last.