Relativity on Earth: Understanding Simultaneity & Time Dilation

[WannabeNewton]

This cannot be correct since $e=1$ defines Einstein synchronization. Where did you read such a thing?

First of all $\epsilon = \frac{1}{2}$ is Einstein synchronization in Grunbaum's framework of synchronization in inertial frames so analyst is perfectly correct. Secondly it is a well known fact that if $\epsilon \in (0,1) - \{1/2 \}$ in an inertial frame then such a synchronization is equivalent to a choice of synchronization for a non-inertial frame. See: http://www.mcps.umn.edu/assets/pdf/8.13_friedman.pdf

 

[xox]

First of all $\epsilon = \frac{1}{2}$ is Einstein synchronization in Grunbaum's framework of synchronization in inertial frames so analyst is perfectly correct.

According to the first paper of the Mansouri-Sexl series, page 501, it is $\epsilon=\pm 1$ that corresponds to Einstein synchronization . For obvious reasons, since one recovers the Lorentz transform from the generalized M-S transform.

Secondly it is a well known fact that if $\epsilon \in (0,1) - \{1/2 \}$ in an inertial frame then such a synchronization is equivalent to a choice of synchronization for a non-inertial frame. See: http://www.mcps.umn.edu/assets/pdf/8.13_friedman.pdf

Thank you, I read this, we are talking about different meanings of $\epsilon$.

 

[WannabeNewton]

Thank you, I read this, we are talking about different meanings of $\epsilon$.

Yes the Mansouri-Sexl formulation and the Grunbaum formulation are different frameworks of synchronization for inertial frames. Sorry for the misunderstanding. I'm almost entirely sure analyst was referring to the Grunbaum formulation.

As an aside, which paper are you referring to? Do you happen to have a link? Thanks in advance.

 

[xox]

Yes the Mansouri-Sexl formulation and the Grunbaum formulation are different frameworks of synchronization for inertial frames. Sorry for the misunderstanding. I'm almost entirely sure analyst was referring to the Grunbaum formulation.

As an aside, which paper are you referring to? Do you happen to have a link? Thanks in advance.

This one (there are two more in the series).

 

[analyst5]

That the two-way speed of light is always $c$? No. Not unless one does the radar echo experiment locally. If the radar echo experiment is performed globally then all kinds of weird things can happen with the two-way speed of light. Just take for example the frame of a uniformly accelerating observer in flat space-time.

Can you perhaps give more detail on this, I'm really interested?

 

[WannabeNewton]

Can you perhaps give more detail on this, I'm really interested?

https://www.physicsforums.com/showthread.php?t=730009

 

[Dale]

To my best knowledge, the Mansouri-Sexl test theory provides for the only two sync methods I listed (Einstein and slow clock transport). SME does not employ ANY form of clock synchronization. I would very much like to learn about the other methods that you are referring to, could you list some references?

Hi xox, sorry about the delay. I was swamped with final training and preparation for my black belt test!

Here is a famous pair of papers on synchronization by Winnie: http://www.jstor.org/discover/10.2307/186029?uid=3739776&uid=2&uid=4&uid=3739256&sid=21104181923193
http://www.jstor.org/discover/10.2307/186671?uid=3739776&uid=2&uid=4&uid=3739256&sid=21104181923193

Here is one by Anderson:
http://www.sciencedirect.com/science/article/pii/S0370157397000513

This one by Debs is about synchronization and the twin paradox:
http://scitation.aip.org/content/aapt/journal/ajp/64/4/10.1119/1.18252

I am sure that there are more, but those are the ones that have come up here in other threads that I have participated in (and learned a lot in). And of course, you are aware of the Mansouri Sexl test theory, so you can plug in different values for the synchronization parameter in that and see what happens.

 

[xox]

Hi xox, sorry about the delay. I was swamped with final training and preparation for my black belt test!

Here is a famous pair of papers on synchronization by Winnie: http://www.jstor.org/discover/10.2307/186029?uid=3739776&uid=2&uid=4&uid=3739256&sid=21104181923193
http://www.jstor.org/discover/10.2307/186671?uid=3739776&uid=2&uid=4&uid=3739256&sid=21104181923193

Unfortunately both are behind the paying wall. From the abstracts, I see no relevance, would you happen to have a copy of the papers that you could share?

Here is one by Anderson:
http://www.sciencedirect.com/science/article/pii/S0370157397000513

This one seems truly relevant and quite interesting. If I were to get a copy, this is the one that I would prefer to get such that we could discuss it. Note that they are not talking about M-S, they are creating their own theory.

This one by Debs is about synchronization and the twin paradox:
http://scitation.aip.org/content/aapt/journal/ajp/64/4/10.1119/1.18252

Don't see any relevance in this one either. I would love to debate the Anderson-Stedman paper, do you have a copy that we could share?

I am sure that there are more, but those are the ones that have come up here in other threads that I have participated in (and learned a lot in). And of course, you are aware of the Mansouri Sexl test theory, so you can plug in different values for the synchronization parameter in that and see what happens.

The only TWO values that I have seen, in ALL the experimental papers that I have read (and I read a LOT of them) are the values (more correctly, functions of $v$) corresponding for Einstein synch and for slow clock transport synch. I understand that you can plug in all kinds of functions of $v$ but I never saw anything different from the two that I just cited. Note that the papers you cited are all theoretical, none of them is experimental.

SME , being based on an extension to the Lagrangian, does not employ ANY form of clock synchronization, either in the photon sector or in the matter sector. Actually, there are NO clocks to be synchronized in ANY of the papers describing the tests. Since SME is taking over from M-S as a foundation for a test theory, the idea of yet another, to be defined, clock synchronization becomes a moot point.

 

[Dale]

Sorry, I don't have non-paywall access, and it is against forum policy to violate copyright, so I cannot just post a copy. I understand the reluctance to purchase.

The only TWO values that I have seen, in ALL the experimental papers that I have read (and I read a LOT of them) are the values (more correctly, functions of v) corresponding for Einstein synch and for slow clock transport synch. I understand that you can plug in all kinds of functions of v but I never saw anything different from the two that I just cited.

The point is that, as you admit, you CAN plug in anything you want. It is a free parameter which is unconstrained by experiment. That people consistently prefer the typical values doesn't change that fact.

Note that the papers you cited are all theoretical, none of them is experimental.

Obviously. Synchronization, as has been mentioned previously, cannot be determined by experiment.

 

[xox]

Sorry, I don't have non-paywall access, and it is against forum policy to violate copyright, so I cannot just post a copy. I understand the reluctance to purchase.The point is that, as you admit, you CAN plug in anything you want. It is a free parameter which is unconstrained by experiment. That people consistently prefer the typical values doesn't change that fact.

My point was a much stronger one: no experimental paper shows any other synchronization than the two I mentioned. None of the three papers that you cited disproves that, actually, the three papers are quite orthogonal to the debate we were having on the subject.

Obviously. Synchronization, as has been mentioned previously, cannot be determined by experiment.

I'm afraid that you missed the point, the papers you cited do not support your earlier claim. Actually, they are totally orthogonal to the claim.

 

[Dale]

My claim was only that we can make different assumptions for our synchronization convention. Clearly we can. All of these papers describe different assumptions that we can make, and the test theory parameter is a completely free parameter.

I am not sure what other claim you think I was discussing. I certainly never made any claims about which synchronization conventions have actually been used by experimental physicists.

 

[xox]

Mansouri-Sexl test theory allows for a wide range of alternative sync methods by varying e.

Yes, I can provide references, but it will have to wait a day or two, apologies.

True, nevertheless, the only two methods that I have encountered in both the original (theoretical) papers and in the experimental applications are Einstein and slow clock transport, no experiment uses another e since Clifford Will's proof that the dependency on e cannot be exposed by experiment. Neither of your three references shows any of use of "alternative synch" in a real life experiment.
Actually, two of the references have nothing to do with the Mansouri theory, the third one is a proper extension to non-inertial frames (rotating).

I certainly never made any claims about which synchronization conventions have actually been used by experimental physicists

True, it is I who did that in my answer to your post. The point is that any "other" synchronization was never used by experimenters.

 

[Dale]

True, nevertheless, the only two methods that I have encountered in both the original (theoretical) papers and in the experimental applications are Einstein and slow clock transport, ... The point is that any "other" synchronization was never used by experimenters.

I never disputed that.

no experiment uses another e since Clifford Will's proof that the dependency on e cannot be exposed by experiment.

That is essentially my point. It cannot be exposed by experiment, it is a matter of convention and we could adopt a different convention.

Actually, two of the references have nothing to do with the Mansouri theory

So what? I claimed that they were different possible assumptions. I did not claim any relationship with other possible assumptions.

You are strangely difficult to communicate with. You seem to think that I am making different claims than what I think I am making, and some of your arguments seem to be actively supporting my position but you state them as though you think that they are contradictory to it. It feels like having a conversation with a particularly smart slot machine.

 

[xox]

So what? I claimed that they were different possible assumptions. I did not claim any relationship with other possible assumptions.

We were discussing the Mansouri-Sexl theory. You provided references that have nothing to do with the M-S theory, despite your promise to provide references supporting your PoV.

You are strangely difficult to communicate with. You seem to think that I am making different claims than what I think I am making, and some of your arguments seem to be actively supporting my position but you state them as though you think that they are contradictory to it. It feels like having a conversation with a particularly smart slot machine.

The fact that you fail to grasp the differences doesn't entitle you to become abusive.

 

[Dale]

The fact that you fail to grasp the differences doesn't entitle you to become abusive.

I do apologize. You are right, that was out of line to compare you to a slot machine. Unfortunately, I was tired and I wrote it and went to bed without re-reading it and toning it down. My sincere apologies.

We were discussing the Mansouri-Sexl theory. You provided references that have nothing to do with the M-S theory, despite your promise to provide references supporting your PoV.

Here is an example of the difficulty in communication that is frustrating me. I claimed (and showed) that we can make different assumptions. The M-S free parameter is a single example, not the sole example, nor did I ever claim that it was the only example. Why should my response be limited to M-S when there are other examples? This is why communication with you feels random. I make a point, provide an example, provide references, and you respond complaining that the references don't make a different point and incidentally mentioning a proof of my point.

Again, my point is only the following: contrary to your statements in post 61 it is well-known in the literature that we do have other synch methods available and we can make assumptions that differ from the standard ones.

That point I have demonstrated. My comments about M-S are only an attempt to build from common ground. Since you are aware of M-S you should have been aware that the synchronization parameter is an example of other synch methods and that the standard one is only a special case. Particularly since you are aware of Clifford Will's proof that experiments cannot fix the synchronization parameter.

 

[xox]

I do apologize. You are right, that was out of line to compare you to a slot machine. Unfortunately, I was tired and I wrote it and went to bed without re-reading it and toning it down. My sincere apologies.

Accepted.

Here is an example of the difficulty in communication that is frustrating me. I claimed (and showed) that we can make different assumptions. The M-S free parameter is a single example, not the sole example, nor did I ever claim that it was the only example. Why should my response be limited to M-S when there are other examples?

Because we were discussing precisely the M-S theory. Because I made it clear that in the M-S theory the only two synchs that I have encountered are Einstein and slow transport, so I was expecting counter-examples to my exact statement as per your answer, this is not what you have provided, so I reacted by pointing this out.

This is why communication with you feels random. I make a point, provide an example, provide references, and you respond complaining that the references don't make a different point and incidentally mentioning a proof of my point.

Actually, it is exactly the other way around. See above.

Again, my point is only the following: contrary to your statements in post 61 it is well-known in the literature that we do have other synch methods available and we can make assumptions that differ from the standard ones.

The exact statement was that I have not encountered any other synchs in the experimental papers based on the M-S theory.

That point I have demonstrated. My comments about M-S are only an attempt to build from common ground.

Well, now you understand why we do not communicate well, I tend to be very precise.

Since you are aware of M-S you should have been aware that the synchronization parameter is an example of other synch methods and that the standard one is only a special case. Particularly since you are aware of Clifford Will's proof that experiments cannot fix the synchronization parameter.

All true. So, are we clear now?

 

[Dale]

All true. So, are we clear now?

Yes? I think.

 

[xox]

Yes? I think.

Good :-)

 

[analyst5]

@Dale, I've red the links you provided, but it added even more confusion to my level of understanding. First thing, I didn't know that velocities change when the one-way speed of light changes. Ok, I understand that it isn't a neccessity that the speed of light is isotropical, and that its limit in an arbitary direction is between c/2 and infinity. I understand that, of course from a perspective of an inertial frame. But what about non-inertial frames, does the same thing apply here? I know that it's a matter of convention, but there should exist some rules for defining the limits like there are in non-standard method of synchronization in inertial frames. Can we consider the speed of light to be 300000 km/s and isotropic in an arbitary convention from our Earth frame, for instance?

 

[analyst5]

And regarding lengths and time dilations viewed from a moving frame, when using a different convention it's possible that the rods increase in coordinate length instead of contracting, and the same applies to time dilation, right?