# Is relativity of simultaneity measurable?

Discussion in 'Physics & Math' started by Pete, May 8, 2013.

1. ### TachBannedBanned

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This debate has been settled at post 95, why don't you go back and read it. The fact that for you, RoS is measurable is not relevant, you need to understand how the mainstream community deals with the issue.

3. ### ash64449Registered Senior Member

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Yeah.. I know that for me if RoS is measurable is irrelevant. But i don't know why it is not measurable. That's all.. So don't i have the right to understand that?

5. ### TachBannedBanned

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Go back to post 95 and read it, it is explained there.

7. ### eramSciengineerValued Senior Member

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I had this RoS experiment quite a few pages back. You could check it out. It is based on operational definitions of simultaneity.

Last edited: Jun 5, 2013
8. ### OnlyMeValued Senior Member

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RoS is a comparrison of measurements made of two events, from two inertial frames. One at rest relative to the events and one in uniform motion relative to the events.

One argument against tests or measurements requires synchronized clocks, which has been pointed out, depends on an assumption that OWLS is constant.., an untestable assumption at this time. Since OWLS is untestable, the validity of synchronization of spacially separated clocks, is also untestable.

Even if one were to overcome the clock issue, the second part of RoS involves the measurement of distance, in both frames. Distance measurements, like the tick rates of clocks, are relative to the frame of rest they are attached to. There is no way to physically measure the distances in the rest frame, where the events take place, from a frame which is moving relative to that frame.

Two events which are simutaneous are very much like proper lengths and times associated with a rest frame relative to those measurements... They cannot be directly measured from any frame which is in motion relative to the rest frame, because the clocks and rulers of the moving frame do not agree with the clocks and rulers of the rest frame.

Events which are simutaneous in a frame at rest relative to the events, will generally be measured as not simultaneous from a frame of reference moving with respect to the rest frame of the simultaneous events.

This always leads the comparrison of measurements back to, "as judged" from the moving frame rather than, "as measured" from the moving frame. Measurements that can be made from the two frames will not agree, which leads to RoS.

Attempting to use Lorentz Transfromations to solve the problem, while it does provide a theoretical conclusion, does not represent a measurement.., thus RoS is not measurable...

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10. ### ShalizRegistered Member

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Thanks for the vid.

11. ### Neddy BateValued Senior Member

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Yes.

No. Events are neither "at rest" nor "moving". They just occur. Using Einstein's example, the embankment frame will say that two lighting strikes hit at A and B simultaneously. The embankment frame does not have to consider that the lighting strikes came from a storm cloud moving at some speed relative to the embankment. That may be true, but it does not factor into RoS at all.

Yes.

Yes, each reference frame makes its own measurements, and those measurements might not match measurements made in some other frame. That's relativity, and it certainly does not mean that RoS cannot be measured. Quite the opposite.

This is all wrong. There is no "as judged" in relativity, there is only "as measured." Using Einstein's example again, the embankment frame measures the lighting strikes to be simultaneous, and the train frame measures them to be non-simultaneous. There is no "judging."

Your conclusion here does not follow from your premise. That is like saying, "Attempting to use F=ma to calculate force provides a theoretical conclusion, but it does not represent a measurement... thus force is not measurable." The conclusion does not follow the premise at all.

Last edited: Jun 6, 2013
12. ### Luis A.C.ROMANELLIDon´t forget using mind ! ! !Registered Senior Member

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Hello Masters ! ! !...First of all excuse My terrible english ! ! !...Now I answer here cause I think that "Layman" wrote a very nice question !!!
He asked if SIMOULTANITY and RELATIVITY could be MEASSURED and I think that I have de answer for that question that is very simple !!!
If we can meassure those items their wouldnt be something that we could manage soooooo...CAN WE MANAGE FOR EXAMPLE ONE OF THE
ITEMS...THE RELATIVITY ENERGY...NO ! ! !...We only can calculate estimations of them and not more than that ! ! !...Atte:LACR

Last edited: Jun 6, 2013
13. ### Luis A.C.ROMANELLIDon´t forget using mind ! ! !Registered Senior Member

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Ok "Tach" I think your words are the correct answer but I havent read them when I wrote My similar answer that are some lines dowm !!!
...................EXCUSE ME !!!...Nave a nice day !!!

14. ### OnlyMeValued Senior Member

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Neddy, I said the frame was at rest not the events. I was not referring specifically to Einstein's hypothetical in this case.

I used the phrase "as judged", mostly as a concession to the analysis given in the paper you cited earlier.

I was not intending to jump back into a discussion of a specific hypothetical. But even your little video link post included length contraction, which involves measurements or judgements of distances... Read back through the paper you linked earlier, one of the test questions dealt with how the moving frame interpreted or judged things to occur in the rest frame. So does the video.

Adding the length contraction in reply to ash64449 was probably an error and over statement. However, Lorentz transformations are not measurements. So explanations that rely on transformations cannot prove measurement. So far I have not seen or have missed the test where everything was measured, from both frames. The closest may have been Einstein's hypothetical, but then based on the discussion here and conclussions from the paper you cited, I am not sure it is the best case or example.

In most of the hypotheicals the moving frame has no real means to directly measure the time of the events.., or even the distances involved. They are always judged to have occurred in a different order than, as measured from a frame at rest relative to the simultaneous events.

Measuring force does not depend on the equation F = ma, but so far the discussions of measuring RoS have depended on the incorporation of Lorentz transforms, so your comparison does not seem to apply.

As I left things with you earlier, it really depends on how you define measure, but I have not seen in this thread any clear definition, of what measure includes.

15. ### Neddy BateValued Senior Member

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OnlyMe,

I believe you understand the concept of proper length, compared to length-contraction. The proper length of the train would be larger than the proper length of the embankment-segment which spans between the lighting strikes. Thus, if you believe length contraction is measurable, then RoS must also be measurable. It's just basic geometry.

Last edited: Jun 6, 2013
16. ### Neddy BateValued Senior Member

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Yes, you do have that right!!

As far as I can tell, there has only been one valid argument against the idea that RoS is measurable. That argument is as follows: "Measuring RoS depends on Einstein's definition of simultaneity, which is not something that is measurable."

17. ### eramSciengineerValued Senior Member

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Hmm, isn't light isotropy measurable?

Hey calm down. You're like ash64449 times ten.

18. ### ash64449Registered Senior Member

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No. Only for round-trip. not for half -trip.

19. ### ash64449Registered Senior Member

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If that's not testable,then how can we validate that RoS is measurable?

20. ### ash64449Registered Senior Member

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I am not like him at all.

21. ### eramSciengineerValued Senior Member

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I've got this scenario, #162 Pg 9

He sounds a lot like you, always seemingly excited and agitated.

22. ### OnlyMeValued Senior Member

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Length contraction is only theoretically measureable. There is no measurement of length contraction in a direct sense. It does not matter what I or you believe. Length contraction is not persistent, for measuring devices moving between frames, in any manner similar to clocks and time dilation, so we have no means to experimentally confirm, any direct measurements and how they differ between frames. Any remote measurements, while they agree and support theory, do not represent direct measurement.

Direct measurements made with real objects which have undergone acceleration.., thus allowing the possibility of measureing proper length in two inertial frames, are only subjected to classical velocities. Even were the length measurements persistent.., the difference would not be itself measurable, given current technology.., any length contraction at classical velocities would be less than measurement limitations. Since length contraction cannot be experimentally proven, any differences in proper lengths associated with objects length contracted relative to each other, is also unprovable.

Theoretically everything fits and agrees with experience. The problem is not all of that experience is based on experimentally proven measurements.

Again, I have to give Pete credit for having made the qualifying, "in principle" distinction.., earlier in this thread.

23. ### eramSciengineerValued Senior Member

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I don't get what you mean, you appear to be rambling and going all over the place.

For instance, you say LC is only theoretically measurable and then suddenly talk about current technology. Then you say experience is not based on experiment. Do clarify cos I may be confused.