Neddy Bate
Valued Senior Member
That is your assessment of chapter 9 of Einstein's 1920 book, linked above? It is just "metaphysics" which is "not much use"?
Is relativity of simultaneity measurable?
- Thread starter Pete
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That is your assessment of chapter 9 of Einstein's 1920 book, linked above? It is just "metaphysics" which is "not much use"?
Please read the last 5 pages, you would lean a lot more than continuing with the trolling. I understand your agenda, it is very transparent.
Neddy Bate
Valued Senior Member
I have no agenda.
http://www.bartleby.com/173/9.html
I would like you to please explain the above link in your own terms.
Although it isn't these days in the realm of "a lab", when you look at stars at night, you are doing a measurement. Simultaneously someone standing next to you and looking at the same stars is doing the same thing.
You can't tell that the light is from a really distant object because you aren't really equipped to measure redshift of spectral lines, nor the expansion of the universe. So to you the light from stars could be moving through the space between it and you at infinite speed. It doesn't change the fact that you and your companion are "doing simultaneous measurements". But how can either of you "prove" it?
Say you have access to any kind of measuring device, what would you use?
You can't tell that the light is from a really distant object because you aren't really equipped to measure redshift of spectral lines, nor the expansion of the universe. So to you the light from stars could be moving through the space between it and you at infinite speed. It doesn't change the fact that you and your companion are "doing simultaneous measurements". But how can either of you "prove" it?
Say you have access to any kind of measuring device, what would you use?
Sure you do, why else ask the question about what is being "measured" in a thought experiment. If you understood the answer , there is no viable followup question, the discussion ends after the answer.
I am quite sure that you and I understand this 93 year old piece quite well, so why would you be so persistent that I spend the time explaining it to you when you know what it means in the first place?
Neddy Bate
Valued Senior Member
In the context of Einstein's thought experiment, the observer at M could use a tape measure to determine that he is located at the midpoint between A and B. Is that the kind of thing you are talking about?
Neddy Bate
Valued Senior Member
My understanding of the thought experiment is that it is useful because it represents what we should logically expect from a real experiment. I was hoping that you could specifically address why you don't think that is the case. Is Einstein's arrangement faulty in some way? Is he ignoring length contraction in the train frame? Is he incorrectly assuming the speed of light to be isotropic and the constant c in both frames? What is your specific argument against his experiment as a means to detect RoS? That is what I would honestly like to know.
Fair enough. For a while there, I thought you were trying to argue that it was impossible to measure two pairs of E-synched clocks disagreeing with each other on whether two events are simultaneous. My mistake. Just one further question:
Sorry, but I can't find an answer in any of your recent posts. Could you link to your answer, or restate it? Thanks!
correct
You are misinterpreting my posts, you will need to go back and read the thread, you will learn that far from me to deny SR prediction of the RoS effect, I have only demonstrated that RoS cannot be measured. To learn why this is so, you will need to go back 5-10 pages and read on the experimental underpinnings of an experiment that would attempt to measure RoS, your time would be much better spent than continuing with the naive and transparent line of questioning. That's all.
Einstein is doing nothing wrong, everything is correct.
Only thing is that for some of us SR has advanced a lot since the 1920 introductory book that seems to be your guide. About 1977 a couple of very good physicists, Reza Mansoury and R.U. Sexl wrote three seminal papers on how to test the effects predicted by SR. Before them, H.P. Robertson wrote another seminal paper on the subject. In short, the three of them produced a very powerful theory (RMS) that is the foundation for the "SR test theories". Much later, in the 90's , Alan Kostelecky came up with an improved version, called Standard Model Extension (SME). RMS and SME prescribe what can be tested and how. RoS is not testable. If you want more detail and if you are genuinely interested in the subject, as you claim, please go back 5-10 pages in the thread and read.
You sure can, ever time I gave you the answer you argued against it. You should have no trouble finding the answers (three times given).
Neddy Bate
Valued Senior Member
So you agree that If Einstein's experiment were made real, the embankment frame should find the lightning strikes to be simultaneous, and the train frame should find the lightning strikes to be NON-simultaneous.
Why doesn't the above count as a "test" of RoS? You can't just say that SR has progressed since 1920, and the new consensus is that RoS is not testable. You have to identify what you are claiming has has changed.
No, I really can't. The only thing approaching an answer I can find is your explanation that there is a big difference between "measuring" and "inferring" the value of a parameter. Is this what you mean? Because if so, it's nowhere near a response to my question. My question is how you can claim that the isotropy of OWLS can be verified to very high precision but the validity of E-synch is unknowable, when your own sources say that the two are equivalent. Whether we verify OWLS by measurement or inference has no bearing on my question.
One last time, with math:
1. $$TWLS = \frac{OWLS_{going}+OWLS_{coming}}{2}$$
This is the definition of $$TWLS$$
2.$$ OWLS_{going}=OWLS_{coming}$$
This is because experiment measures $$OWLS$$ to be isotropic (within $$10^{-17}$$ and getting tighter), the anisotropy constrainment measurements do not use any clocks, much less E-synch, contrary to your repeating the same misconception over and over
3. It follows from the above that :
$$ OWLS_{going}=OWLS_{coming}=TWLS$$
See post 278. Gedanks are not tests. The former is run in your mind, the latter is run in the lab. You should try to get in the lab sometime, this might help you in not confusing one with the other, a mistake that you persist in.
Go back 10 pages and start reading, all the details are there. I am not going to repeat 10 pages of details, Pete and Fednis finally understood, hopefully so can you.
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Yeah, I got that. You just confirmed, in detail, why you think OWLS can be determined (to one part in $$~10^{17}$$) experimentally. But that isn't my question! Even though you say OWLS can be determined to high precision experimentally, you maintain that the validity of E-synch, which is equivalent to the isotropy of OWLS, is untestable and must be established by convention. Two equivalent things must either be both testable or both not; to say otherwise is self-contradictory. How are you not contradicting yourself?
You obviously missed the key part: the anisotropy constrainment measurements do not use any clocks, much less E-synch, contrary to your repeating the same misconception over and over.
Ok, I see where you're coming from now. But according to your own link, the E-synch convention "is equivalent to the requirement that the one-way speeds of [a] ray be the same on the two segments of its round-trip journey between A and B." No matter how you measure your constraints, "OWLS is isotropic" and "E-synch is correct" are two different ways of saying the same thing. Do you think the linked page is wrong to say this?
You seem unable to get your notions right:
1. E-synch depends on OWLS, by definition.
2. OWLS anisotropy measurement does not depend on E-synch, as explained repeatedly, its measurement does not rely on E-synch, actually does not rely on clocks at all. All that it is required is a measurement of OWLS anisotropy, not a measurement of OWLS.
3. As an aside: do you understand the difference between "measuring OWLS" and "measuring OWLS anisotropy"? Based on your repeating the same question over and over, not.
That's my understanding from your link. More specifically, E-synch is right if and only if OWLS is isotropic.
Whether or not you actually need to use E-synch to measure OWLS anisotropy is beside the point. Since the two are equivalent, any experiment that demonstrates OWLS isotropy also demonstrates the validity of E-synch. This is true by definition, whether or not the experiment actually uses any clocks.
Of course. If OWLS anisotropy could be measured, it would be possible to devise an experiment that shows OWLS is isotropic (to within small uncertainty) without actually giving the magnitude of OWLS. An experiment that actually measured OWLS would give its magnitude in addition to showing its isotropy. But that's beside the point, because E-synch is equivalent to the isotropy of OWLS, so we wouldn't need to know the magnitude of OWLS to prove the validity of E-synch.
Neddy Bate
Valued Senior Member
Well then tell me this: If Einstein's thought experiment were to be performed as a REAL experiment, do you think the results would be any different than the gedanken?