Is relativity of simultaneity measurable?

[Tach]

oops

Yep.
Do you think you can help Fednis48 find his mistakes?

 

[Fednis48]

These calculations, on the other hand, are not correct.

Oh, really? What's wrong with them? I just did those calculations off-the-cuff, so I'm not 100% sure they're error free. But except in the context of a teacher/mentor relationship (which this is definitely not), the non-sociopathic option is to point out errors for speedy resolution rather than asking the error-maker to track them down.

I think that you may want to go back and read post 95, it explains why the mainstream physicists know that "RoS tests" cannot be performed. Pete is starting to come to grips with the idea.

Good point. It took me a while to understand the stuff you linked to in post 95, so I'll try my best to explain it to other people who may not have read the pages

If we want to be really rigorous when we look at reference frame transformations, we can only make a few, basic assumptions. One is that there are three spatial dimensions and one temporal dimension, and another is that all three spatial dimensions behave the same way. (There may be even more general theories in which the universe treats, say, y-coordinates differently from z-coordinates, but the test theory on Wikipedia assumes spatial symmetry.) Making just these two assumptions and leaving all the other parameters as free variables, Mansouri and Sexl came up with a generalization of the Lorentz transform which could be compared with experiment to test SR. Three of the four variables can be tested for agreement with SR. The fourth variable, "e", depends on how we synchronize spatially separated clocks (ie. how we define "simultaneous"), and cannot be tested experimentally. This is why, at the most fundamental level, there is not and never will be an experimental test of RoS. In eram's example for which I gave the equations above, I'm guessing the loophole is that you can't measure the velocity of a distant object with a radar gun unless you know e.

Of course, like Pete said, rejecting RoS based on this fact comes at a heavy price. For the same reason that it's technically impossible to demonstrate RoS, it's technically impossible to know that two spatially distant events are simultaneous in a given reference frame. To put it another way, RoS implies that two observers might disagree on whether two events are simultaneous. But according to the more general theory, even just one observer can never know whether he/she is seeing simultaneous events.

To get around this (admittedly profound) technicality, we have to assume that the speed of light does not depend on whether the light is travelling toward or away from the detector. In the jargon, we have to assume that light's "one-way speed" is the same as its "two-way speed". This is equivalent to assuming that if we take two synchronized clocks and move them apart slowly, they will remain synchronized. These seem like pretty reasonable assumptions, but there's no way to prove them. Kudos to Tach for pointing that out.

Of course, having said that, there's also this:

This is really bad, your AND gate will produce a solid "1" in one frame and a glitch to "0" in the other frame.

Come on. It's one thing to say that eram's experiment makes assumptions about the one-way speed of light. It's entirely another to say that it will give unphysical results. As I explained it, the AND gate will produce a "1" in both frames because of RoS. Revising that statement for rigor, the gate will produce a "1" in both frames either because of RoS or because of bizarre effects due to the one-way speed of light. But either way, the gate will definitely say "1" for all observers. To say otherwise is downright bizarre.

 

[Tach]

Oh, really? What's wrong with them? I just did those calculations off-the-cuff, so I'm not 100% sure they're error free. But except in the context of a teacher/mentor relationship (which this is definitely not), the non-sociopathic option is to point out errors for speedy resolution rather than asking the error-maker to track them down.

There are benefits in you finding your own errors. You made several. Insulting me will not convince me to point them out to you, this is a simple SR exercise, you messed up the solution, you find your own errors.

This is why, at the most fundamental level, there is not and never will be an experimental test of RoS.

Good, you are starting to get it. We should close this thread right here. We can open a different thread with eram's exercise, so you can work through it without hijacking this thread. Maybe you can have Pete move the posts pertaining to eram's exercise in a different thread.

In eram's example for which I gave the equations above, I'm guessing the loophole is that you can't measure the velocity of a distant object with a radar gun unless you know e.

It is much more basic than that, you made quite a few errors in setting up the equations describing the experiment.

Come on. It's one thing to say that eram's experiment makes assumptions about the one-way speed of light. It's entirely another to say that it will give unphysical results. As I explained it, the AND gate will produce a "1" in both frames because of RoS. Revising that statement for rigor, the gate will produce a "1" in both frames either because of RoS or because of bizarre effects due to the one-way speed of light. But either way, the gate will definitely say "1" for all observers. To say otherwise is downright bizarre.

What I am saying is that your equations contain several basic errors. It would be beneficial for you to try reworking them, the errors start from the very beginning.

 

[Trooper]

Then what are you doing in this forum? Eh?

I want to see if you’re wrong or right. Because you continually push, not only the report button, but everyone's buttons.

The final deciding factor was that Tach maintains that parallelism of vectors is Lorentz invariant, despite clearly agreeing just a couple of posts previously that vectors parallel in S are not necessarily parallel in S'.

This is your premise, the jury is out on its validity. All proofs I have shown prove the opposite, i.e. zero angles are Lorentz invariant.

 

[Fednis48]

There are benefits in you finding your own errors. You made several. Insulting me will not convince me to point them out to you, this is a simple SR exercise, you messed up the solution, you find your own errors.

Do you not realize how incredibly narcissistic this makes you sound? In a context with no clear "authority" on the subject being discussed (like, say, an internet forum), everyone has to make a case for his/her own arguments. That's how productive discussion works. Saying "You're wrong, but I won't tell you why, because it would be more educational for you to figure it out yourself." tells me that you're working under the assumption that you do not make mistakes. Which is simply wrong.

Assuming you still aren't willing to actually identify a mistake, though, can you at least narrow it down? Is it an error of physics (ie. writing the wrong equations) or of algebra (ie. solving the equations incorrectly)?

Good, you are starting to get it. We should close this thread right here. We can open a different thread with eram's exercise, so you can work through it without hijacking this thread. Maybe you can have Pete move the posts pertaining to eram's exercise in a different thread.

You might be right. My only concern is that, while RoS is not rigorously testable, the reasons why don't have much bearing on the thread(s) off of which this was spun. The other thread(s) were working on puzzles in SR, and you implied that the RoS in those contexts was not measurable. In this thread, you've shown that RoS is not testable because SR might be wrong. Since the other thread(s) assumed the accuracy of SR, it's safe to say they also assumed the correctness of Einstein clock synchronization. And eram's example shows how we can observe RoS to the extent that we assume Einstein clock synchronization is accurate. In that respect, I'd say eram's example is still on-topic. That's ultimately for Pete to decide, though.

 

[Tach]

Do you not realize how incredibly narcissistic this makes you sound? In a context with no clear "authority" on the subject being discussed (like, say, an internet forum), everyone has to make a case for his/her own arguments. That's how productive discussion works. Saying "You're wrong, but I won't tell you why, because it would be more educational for you to figure it out yourself." tells me that you're working under the assumption that you do not make mistakes. Which is simply wrong.

We are discussing your mistakes.

Assuming you still aren't willing to actually identify a mistake, though, can you at least narrow it down? Is it an error of physics (ie. writing the wrong equations) or of algebra (ie. solving the equations incorrectly)?

A and B arrive simultaneously at the midway point in frame $$S$$.
This means that A and B arrive simultaneously (in a different point, you will need to calculate it , something that you haven't done correctly) in frame $$S'$$.
Actually, A and B will arrive simultaneously in the same point, in all frames. As such, eram's setup cannot be used to measure any RoS since it is a garden variety example of absolute simultaneity. Of course, you knew that.
In addition to the above gross error, you made errors in calculating $$T'_A,T'_B$$. But these errors take a back seat to your first error.

And eram's example shows how we can observe RoS to the extent that we assume Einstein clock synchronization is accurate. In that respect, I'd say eram's example is still on-topic.

You still maintain this in light of your basic fumble?

 

[Tach]

I want to see if you’re wrong or right. Because you continually push, not only the report button, but everyone's buttons.

So, by your own admission, you do not know physics. You can't decide for yourself is my posts are right or wrong, so why watch them altogether

 

[Tach]

duplicate

 

[Pete]

This thread will be closed for couple of days, because the discussion is becoming obstructed and the conversation is becoming unruly. Everyone take a breath, we'll start again after a break.

Tach, you seem to be playing a childish point-scoring game. That is not acceptable. This forum is for mutual learning and discovery, it's not a place for virtual phallus waving. If you're here to 'win' then you're in the wrong place.

Trooper, Fednis48, I'm asking you to please don't let Tach push your buttons. I know it's difficult, but if you post an insult and Tach tattles, then I'm required to take action.

Everyone, report insults if you must, but if a post contains both insult and content, it's better to ignore the insult and respond to the content.

Obstruction of discussion is more serious, and should probably be reported (or PM me) if you can't resolve the block after a couple of posts. For example, if you ask an explicit question which is ignored, post it again. If it is still ignored, it's OK to report it.

Cheers, Pete

 

[Pete]

Thread reopened.

I concede that relativity of simultaneity is not measurable unless we first assume without proof that the speed of light is frame independent. The mathematical formulation of the family of transformations that are consistent with experiment (o which the Loretnz transform is but one) feel interesting, if anyone wishes to engage in polite discussion.

I'm happy to leave Tach in the philosophical hole he has retreated into.
I've just read through the other two threads [thread=134429]Basic Special Relativity Question[/thread] and [thread=134380]Relativity Paradox[/thread].
Tach's appalling treatment of other posters, and his pugilistic and obstructive 'discussion' style leaves me no stomach to continue discussing anything with him. It might be interesting to summarise the various contradictory stands he has taken, all without one admitting a previous stand was wrong, but it would feel like kicking a puppy who really wants my shoe. So go on, Tach. Take the shoe. It's yours.

 

[Trooper]

I could be wrong because I just skimmed the arguments, but based on Tach’s history, this is what I think happened. He made the mistake of claiming that the angles were invariant, and then moved the goalpost to the conventionality of simultaneity.

I’m not quite sure how Pete is defining the term "in principle", but I agree with Tach that it is a convention.

Einstein synchronisation is a convention for synchronising clocks at different places by means of signal exchanges.

In physical sciences, numerical values (such as constants, quantities, or scales of measurement) are called conventional if they do not represent a measured property of nature, but originate in a convention, for example an average of many measurements, agreed between the scientists working with these values.

I just noticed that Pete conceded. Good deal!

All's well that ends well.

 

[Tach]

Thread reopened.

I concede that relativity of simultaneity is not measurable unless we first assume without proof that the speed of light is frame independent.

This is incorrect on two accounts:

1. There is ample experimental proof that light speed is frame independent.
2. Relativity of simultaneity is not measurable period, independent of the assumptions on light speed.

I'm happy to leave Tach in the philosophical hole he has retreated into.

This is not a hole and it is not philosophical. Experiment (practice) precludes any measurement of RoS.

 

[Pete]

1. There is ample experimental proof that light speed is frame independent.

As I'm sure you're aware, the only possible experimental proof is for two-way speed, not one-way.

 

[Pete]

There are benefits in you finding your own errors. You made several. Insulting me will not convince me to point them out to you, this is a simple SR exercise, you messed up the solution, you find your own errors.

It is much more basic than that, you made quite a few errors in setting up the equations describing the experiment.

What I am saying is that your equations contain several basic errors. It would be beneficial for you to try reworking them, the errors start from the very beginning.

We are discussing your mistakes.

You still maintain this in light of your basic fumble?

This obstructionist behavior is effectively trolling, and is not acceptable. Tach, you are not a teacher. If you see an error, point it out explicitly.

 

[OnlyMe]

This is incorrect on two accounts:

1. There is ample experimental proof that light speed is frame independent.

"Ample" for what? All experimental results that reach any precision, have been conducted locally. Projecting conclusions based on locally conducted experiment is anything but "ample" proof of a universal or global extension. The universal nature of conclusions drawn from locally defined experiments remains theoretical.., not proven universally or globally.

2. Relativity of simultaneity is not measurable period, independent of the assumptions on light speed.

This is not a hole and it is not philosophical. Experiment (practice) precludes any measurement of RoS.

It seems that I asked you directly whether you were saying that with today's technology RoS was unmeasurable.., and you agreed that with today's technology it is measureable.

Is this current argument about the SR hypothetical or a scientifically acceptable experimental proof of RoS? (Understanding that is a rare thing that any experiment is accurate to a certainty.)... Or is this a semantic objection to the use of "experimentally measure", rather than "experimentally confirm"?

 

[Tach]

As I'm sure you're aware, the only possible experimental proof is for two-way speed, not one-way.

Given the way the experiments are constructed, your claim is incorrect. See here. There is no "two way" , in any of the cited experiments.
When I see the errors in your posts , I point them out explicitly , exactly the way you asked me to.

 

[OnlyMe]

Given the way the experiments are constructed, your claim is incorrect. See here. There is no "two way" , in any of the cited experiments.
When I see the errors in your posts , I point them out explicitly , exactly the way you asked me to.

Tach, your link goes to section, "3.3 Tests of Light Speed from Moving Sources", which refers to astronomical data, based on the underlying assumption(s).

The previous section, "3.2 One-Way Tests of Light-Speed Isotropy", lists a number of experiments with limits on the anisotrophy of c (sometimes listed as one way anisotrophy) from 100 m/s to at best the refrence quoted below of 0.13 m/s.

from sec 3.2 One-Way Tests of Light-Speed Isotropy from Tach's link
Ragulsky, “Determination of light velocity dependence on direction of propagation”, Phys. Lett. A, 235 (1997), pg 125.
A “one-way” test that is bidirectional with the outgoing ray in glass and the return ray in air. The interferometer is by design particularly robust against mechanical perturbations, and temperature controlled. The limit on the anisotropy of c is 0.13 m/s.​

There is no one way speed of light experiment that approaches the accuracy of two way speed of light experimental data. And you can see from the variety of experiments referenced that they have not reached agreement. There is always that "within the limit of" disclaimer, attached.

P.S. to correct the first part of my post above section 3.3 does include several terrestrial experiments, but they all either include similar limitations on the accuracy or are not attempting to measure a one way speed of light... Example — the following measures the effect of a moving glass plates on the measured speed of light.

Babcock and Bergmann, Journal Opt. Soc. Amer. Vol. 54, pg 147 (1964).
This repeat of Kantor's experiment in vacuum shows no significant variation in the speed of light affected by moving glass plates. Optical Extinction is not a problem. k < 0.02.
​

 

[Neddy Bate]

Tach's argument has never been, "Your proposed experiment does not test RoS because your experiment is founded on Einstein synchronization which assumes the speed of light is the same in both directions."

Post 95 shows your claim to be exactly false.

In that case, you should have said so much earlier.

Relativity of simultaneity is not measurable period, independent of the assumptions on light speed.

 

[Pete]

As I'm sure you're aware, the only possible experimental proof is for two-way speed, not one-way.

Given the way the experiments are constructed, your claim is incorrect. See here. There is no "two way" , in any of the cited experiments.

Same link, previous section:

Note that while these experiments clearly use a one-way light path and find isotropy, they are inherently unable to rule out a large class of theories in which the one-way speed of light is anisotropic. These theories share the property that the round-trip speed of light is isotropic in any inertial frame, but the one-way speed is isotropic only in an aether frame. In all of these theories the effects of slow clock transport exactly offset the effects of the anisotropic one-way speed of light (in any inertial frame), and all are experimentally indistinguishable from SR. All of these theories predict null results for these experiments.​

I'm surprised you're arguing that one way speed of light is measurable, because in post 95 you explicitly said that it is not:

...you cannot measure OWLS because it requires two synched clocks that turn out to be synched based on measuring .... OWLS.

 

[Tach]

Same link, previous section:

Note that while these experiments clearly use a one-way light path and find isotropy, they are inherently unable to rule out a large class of theories in which the one-way speed of light is anisotropic. These theories share the property that the round-trip speed of light is isotropic in any inertial frame, but the one-way speed is isotropic only in an aether frame. In all of these theories the effects of slow clock transport exactly offset the effects of the anisotropic one-way speed of light (in any inertial frame), and all are experimentally indistinguishable from SR. All of these theories predict null results for these experiments.​

I'm surprised you're arguing that one way speed of light is measurable, because in post 95 you explicitly said that it is not:

You are mixing up two different effects:

1. OWLS isotropy (this is NOT what the experiments are about)

2. OWLS (in)dependence of source-detector relative speed (this IS what the experiments are about, such experiments do not measure OWLS but its independence of the relative speed between source and detector, as the website teaches you).

You are making the same exact mistake as OnlyMe in his post above by mixing up two different classes of experiments:

a. One measures OWLS independence wrt direction, the other measures OWLS independence wrt source-detector speed.

b. Neither is TWLS, neither measures the OWLS value (because, indeed , such a measurement is impossible).

The bottom line is that the experiments measuring the light speed independence of the source-detector relative speed are NOT two-way light speed, contrary to your earlier claim. This is what the website is telling you.