Absolute Time Clock Experiments: Einstein's Special Relativity

[Dale]

please try to give me another example from physics, be it any kind of Pre-SR physics, in which, in certain conditions, it is not possible to measure something, no matter what you do, and that there is a theory that backs it up, as completely legitimate.

You are correct in principle. Such a theory would be unfalsifiable and therefore non-scientific. SR is definitely falsifiable as there are many ways to measure its experimental predictions, so this comment certainly doesn't apply to SR.

 

[TrickyDicky]

Roineust, I think it is important to understand that every law, every postulate in science has a certain scope of application, SR is no exception. You are asking of it something it was not meant to solve, Einstein himself repeatedly said that all SR had to say about the ether is that it was an unnecesary (superfluous) assumption in the range where SR applies, which is an idealized space (minkowskian) where masses can be neglected and all frames are inertial in the Newtonian sense (uniform velocity). This is obviouly a mathematical idealization that is not our real universe but that happens to work very well for problems where one doesn't have to take into account gravitation , which are quite a lot (all EM applications,weak force, etc ...) because the gravitational interaction is very small to be detected by our experiments , like in the particle accelerator experiments you cite (it is within experimental error bars).
If you want to take those gravitational effects into account you have to turn to GR, there you will find that in practical terms an ether is used (even though you can't use the taboo word ether, it is frowned upon due to historical connotations). An absolute rest frame is considered for a certain set of "fundamental observers". This absolute rest frame is realized for instance in the form of the CMB that fills the vacuum. Of course you'll be told that it is not a "real" absolute rest frame but in practical terms is used as if it were because otherwise we can't concoct a coherent cosmic time line, or in other words the absolute clock you seek is been around for decades, is the one that counts the time from the BB to now.

 

[roineust]

If what you say is correct,
For me at least, it is a big surprise!

So now, if indeed so, I might have a whole new set of questions.

But first I want to be sure that the device I am asking about (Please look at the 'Michelson–Morley experiment?' thread), will indeed function, as an absolute clock or let it be an 'absolute clock' (This is still not clear as well).

But, I don't think that this is the situation - that is, I am trying to understand, the reason to what seems to be the common consent - that neither an 'absolute clock' nor an absolute clock is possible.Roi.

 

[Dale]

If you want to take those gravitational effects into account you have to turn to GR, there you will find that in practical terms an ether is used (even though you can't use the taboo word ether, it is frowned upon due to historical connotations).

It is not just a matter of historical connotation. The metric of GR has nothing to do conceptually with the luminiferous aether of the early 20th century. They are simply unrelated concepts and to use the same label is deceptive. The defining property of the aether was velocity, a property which the metric does not have, and the defining property of the metric is curvature, a property which the aether did not have. It is not simply a matter of social custom and taboo, the concepts themselves are too different to be identified with one another.

Think of all of the problems that have arisen in QM due to their continued use of the word "particle" to describe a quantum concept which is very different from the classical notion of a particle. Calling the metric "aether" would lead to similar confusion.

 

[TrickyDicky]

It is not just a matter of historical connotation. The metric of GR has nothing to do conceptually with the luminiferous aether of the early 20th century. They are simply unrelated concepts and to use the same label is deceptive. The defining property of the aether was velocity, a property which the metric does not have, and the defining property of the metric is curvature, a property which the aether did not have. It is not simply a matter of social custom and taboo, the concepts themselves are too different to be identified with one another.

Well, let's not call it ether if it can be confusing, I certainly wasn't talking about the "luminiferous ether" pre-Einstein, but to the ether referred by Einstein in many occasions in relation with GR like his "Ether and the Theory of Relativity" from may 1920.
Let's call it an absolute rest frame that is implicit in the GR equations when solved with any metric and coordinates. You just have to realize that GR is not Lorentz invariant when applied to any realistic cosmological object (with mass).

Think of all of the problems that have arisen in QM due to their continued use of the word "particle" to describe a quantum concept which is very different from the classical notion of a particle.

Totally agree. I actually think the word "particle" has been more of a problem in QM, than the word "ether" in GR.

 

[harrylin]

It is not just a matter of historical connotation. The metric of GR has nothing to do conceptually with the luminiferous aether of the early 20th century. They are simply unrelated concepts and to use the same label is deceptive. The defining property of the aether was velocity, a property which the metric does not have, and the defining property of the metric is curvature, a property which the aether did not have. It is not simply a matter of social custom and taboo, the concepts themselves are too different to be identified with one another.

Think of all of the problems that have arisen in QM due to their continued use of the word "particle" to describe a quantum concept which is very different from the classical notion of a particle. Calling the metric "aether" would lead to similar confusion.

Probably you meant the luminiferous aether of the 19th century. The defining property of the Lorentz ether is that its velocity cannot be used as reference for a metric. Therefore, Einstein stated that the ether of GRT is based on the Lorentz ether. Its main difference is that its properties are affected by matter, which is a feature that Lorentz's pre-GRT ether lacked.
But I agree with your comment about the confusing use of the word "particle" in QM, and certainly the metric ("the map") should not be confused with the physical model ("the territory") that one may invent to make sense of the metric.

Harald

 

[Dale]

The defining property of the Lorentz ether is that its velocity cannot be used as reference for a metric.

The Lorentz aether was still attributed a velocity, it is just that it also had other ad-hoc properties (caused length contraction in moving rods) that conspired to make the velocity unmeasurable.

 

[roineust]

OK,
This is not the first time I am asking this question.
But in my opinion , I did not get a clear enough answer to that question.

If there are people, who think that, they already gave me the full answer, and that I am just repeating myself - Please! I am really sorry! excuse me, and just ignore this message. In that case, please spare me the berate.Here is a diagram.
It takes into consideration time dilation (clock C), the constancy of the one way of the speed of light in inertial frames, and a slow transport synchronization of the clocks A and B, synchronized once in the inertial stationary frame, and once in the inertial moving frame (second sync, only after the moving frame becomes inertial).

The diagram depicts, what is considered **not a true** scenario: clock A and clock B , in the moving frame, do not turn on together (the blue and white circles).

My question is, why is this scenario wrong? What is it that causes the true scenario to be, that both detectors in the moving frame turn on together? e.g. both circles in the moving frame should be blue as well.

Thanks,
Roi.

 

[harrylin]

The Lorentz aether was still attributed a velocity, it is just that it also had other ad-hoc properties (caused length contraction in moving rods) that conspired to make the velocity unmeasurable.

No matter what model of nature one likes to use with SR, it has to obey the PoR.

 

[harrylin]

OK,
This is not the first time I am asking this question.
But in my opinion , I did not get a clear enough answer to that question.
[..]
The diagram depicts, what is considered **not a true** scenario: clock A and clock B , in the moving frame, do not turn on together (the blue and white circles).

My question is, why is this scenario wrong? What is it that causes the true scenario to be, that both detectors in the moving frame turn on together? e.g. both circles in the moving frame should be blue as well.

Thanks,
Roi.

What you perhaps did not understand:

Assume that a system (a real platform) has two similar clocks are side by side, in rest on that platform. Its two clocks are synchronized with each other.
Now the clocks are separated with identical motors that push them an equal distance in opposite directions. According to an observer on the platform who considers himself in rest, the clocks must still be in tune with each other.

However, according to you, that platform is moving fast to the left.

According to your measurements, the clocks on that platform are ticking slower due to the fact that they move along with that platform. Now, when a clock is transported to the left, it will move faster than the platform. And when a clock is transported to the right, it will move slower than the platform.
Therefore, according to your measurements, the clock that is transported to the left will be ticking slower, during that transport, than the clock that is transported to the right.
That exactly compensates for the difference in time delays of the light rays that you expect.

 

[roineust]

But what I understood was, that the whole point in the slow transport technique, is that by moving the synchronized clocks apart slow enough, this movement does not need to be included, in any calculation of the scenario...

 

[harrylin]

But what I understood was, that the whole point in the slow transport technique, is that by moving the synchronized clocks apart slow enough, this movement does not need to be included, in any calculation of the scenario...

Slow transport is only slow relative to the platform on which the clocks are transported. Clocks that are slowly moved over a not too far distance will remain approximately synchronized with other clocks in that system - according to the platform's synchronization with light rays!

Didn't you understand Einstein's train example? Distant clocks along the direction of motion that are synchronous according to the moving platform, cannot be also synchronous for the rest platform.

As I formulated it, the transport may be fast: both clocks will always remain exactly synchronized with each other for the moving platform. For your example it doesn't matter if they are both behind, as long as they are equally behind.

Thus, and I repeat:
According to your measurements on a stationary platform of the moving platform, the clock that is transported to the left will be ticking slower, during that transport, than the clock that is transported to the right.
That exactly compensates for the difference in time delays of the light rays that you expect.

 

[roineust]

What I don't understand is the relation between experiment and PoR:

For proving that there is time dilation in clock C, you have got to have another clock in the stationary frame, in order to measure this time dilation.

But, what need is there for measurement outside the moving frame, relating to what happens between clocks A and B. This synchronization process is done only between clocks A and B, so where and how arises experimentally the act of measuring from outside the moving frame, what happens between clock A and B?

 

[harrylin]

What I don't understand is the relation between experiment and PoR:

For proving that there is time dilation in clock C, you have got to have another clock in the stationary frame, in order to measure this time dilation.

But, what need is there for measurement outside the moving frame, relating to what happens between clocks A and B. This synchronization process is done only between clocks A and B, so where and how arises experimentally the act of measuring from outside the moving frame, what happens between clock A and B?

I don't understand your question. Did you understand my answers?

The relation between experiment and PoR is that both systems measure what you drew at the top; any inertial platform may be pretended to be "in rest".

 

[roineust]

Here is a diagram.
It takes into consideration time dilation (clock C), the constancy of the one way of the speed of light in inertial frames, and a slow transport synchronization of the clocks A and B, synchronized once in the inertial stationary frame, and once in the inertial moving frame (second sync, only after the moving frame becomes inertial).

The diagram depicts, what is considered **not a true** scenario: clock A and clock B , in the moving frame, do not turn on together (the blue and white circles).

My question is, why is this scenario wrong? What is it that causes the true scenario to be, that both detectors in the moving frame turn on together? e.g. both circles in the moving frame should be blue as well.

Is there an experiment that was done in the past, that can be considered equivalent, as a whole, to this device, and that is possible to indicate within that experiment, the exact equivalent elements, not only of C clock, but also of both A and B clocks?

Thanks,
Roi.

 

[Dale]

Is there an experiment that was done in the past, that can be considered equivalent, as a whole, to this device

See:
http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html

In particular the section on time dilation and the section on the speed of light. Your device does not involve anything else.

 

[roineust]

How come experiments could not resolve, to total agreement, the question of the constancy of the one way speed of light? How could slow transport, influence that question anyway? Say someone thinks that slow transport actually does influence the clocks - So then he should take into consideration slow transport - how does that make the results of experiments show that the one way of the speed of light is not constant? Is the claim of these theories, that it depends on the specificities of the scenario? How? Weren't experiments made testing different scenarios?

 

[harrylin]

How come experiments could not resolve, to total agreement, the question of the constancy of the one way speed of light? How could slow transport, influence that question anyway? Say someone thinks that slow transport actually does influence the clocks - So then he should take into consideration slow transport - how does that make the results of experiments show that the one way of the speed of light is not constant? Is the claim of these theories, that it depends on the specificities of the scenario? How? Weren't experiments made testing different scenarios?

Again, I don't understand your questions as you claim the opposite of what I explained and which you did not comment or ask about. Running away from the answers on your questions only accumulates confusion on error...

I'll answer once more the same as before, contrary to what you claim:

The effect of fast and slow transport is exactly as the theory predicts as experiments confirm. For your example, fast transport is perfectly fine too. One should take into consideration the effect of clock transport to show that although the one way speed of light is constant, the relativity principle still works. The scenario doesn't matter, that's the whole point.

Good luck,
Harald

PS Did you perhaps not understand that the constancy of the speed of light and the relativity principle are in apparent contradiction? That's how the development of relativity theory started.

 

[Dale]

How come experiments could not resolve, to total agreement, the question of the constancy of the one way speed of light?

Because that is a matter of definition, not experiment. Specifically, the one-way speed of light is completely determined by your (arbitrary) choice of synchronization convention. The Einstein synchronization convention defines simultaneity in an inertial reference frame, but other conventions are possible.

 

[roineust]

I began my whole journey, regarding SR, from a statement that says, that it is not possible to determine a relative inertial change, from within the ship, without looking out of the ship's window (which stands for several possibilities of observation and communication with the outside world) or without feeling the acceleration that led to this inertial change (which stands for several possibilities for detecting acceleration).

Now: Is this statement also a matter of definition? Can you give me a simple example for how such a statement, which is a statement that can be understood to a very high intuitive degree, can be defined in several ways, and not just in one way? Is that statement a matter of convention as well?

 

[Dale]

Is this statement also a matter of definition?

No. See sections 3.5 and 3.6 of the above reference.

 

[roineust]

OK,
So how come experiment results, such as in sections 3.5, 3.6, that are not a matter of convention, but agreed upon according to all conventions, results in multiple conventions? Aren't such experiments, considered some sort of fundamental physical basis, that only on it, is it possible to build a mathematical definition? Isn't there in physics, some fundamental group of experiments, that are considered singularly truth, without regards to convention - and only on this group of experiments, the mathematical definitions are built?

 

[Dale]

So how come experiment results, such as in sections 3.5, 3.6, that are not a matter of convention, but agreed upon according to all conventions, results in multiple conventions?

What?

Aren't such experiments, considered some sort of fundamental physical basis, that only on it, is it possible to build a mathematical definition? Isn't there in physics, some fundamental group of experiments, that are considered singularly truth, without regards to convention - and only on this group of experiments, the mathematical definitions are built?

Defined quantities are not restricted to things which are experimentally measurable. For example, a potential is not measurable due to the possibility of gauge transformations, but it can easily be defined.

 

[roineust]

This still doesn't explain the relation between, the one way speed of light, slow transport and an experimental action.

Say we have the usual two frames, one called "moving" the other called "stationary".

The moving frame, is a jet flying a device. The Stationary is the on-ground station with the same device. This device has two clock-light-detectors. These two identical devices' two clocks each, are both separated by a slow transport mechanism, only after their frames are fully inertial relatively to one another.

One theory will claim that, because of the affect of slow transport mechanism of separating the clocks, no matter how slow, the on-ground clock will measure the speed of light as X and the jet device measures the speed of light differently, say as Y.

The other theory will claim that the slow transport mechanism, doesn't change the measurements results in comparison between the two frames, exactly because the separation of the two clocks, is done slowly, and that both on-ground and jet devices, will measure the speed of light to be the same, let it be X and X or Y and Y or Z and Z.

Now, here you probably, already know what I don't understand. Putting such a device on a jet is very feasible- and the experimental result can be true to only one of the theory types above ,and not to both.

So how come conventions or definitions, change measurements in this case, of having only one true answer, regarding the constancy of the one way speed of light?

 

[ghwellsjr]

Roi,

Any "theory" that predicts that an experiment performed on an inertially "moving" platform (like a jet) will get any different result than when performed on an inertially "stationary" platform (like the earth) will be an invalid theory and will be discarded because it does not comport with reality.

Every experiment performed on any inertial platform (one that is not accelerating) will appear exactly the same as if it were performed at rest with respect to an absolute ether rest frame. The one way speed of light will appear to be the same in all directions, no matter how you attempt to measure it. The round-trip speed of light will appear to be a constant in all directions, no matter how you attempt to measure it. There will be no detectable ether wind, no matter how you attempt to measure it. All identical distant clocks at rest in this frame can be synchronized by many different methods and all appear to run at the same speed. All identical rulers at rest in this frame will appear to be the same length no matter their orientation or location. There is no experiment that you can perform on any inertial platform that will behave any differently than it would on any other inertial platform. These characteristics have nothing to do with any theory, or any convention, or any definition; they are just the way nature works.

Do you question any of these facts? Do you have any doubt about the truthfullness of any of these statements?

 

[JesseM]

I haven't read this whole thread, but a question for roineust: do you understand that according to relativity, if there's a rocket moving at relativistic velocity relative to us, and two clocks on board the rocket are synchronized at a single location and moved apart with slow velocities relative to the rocket, then in our frame the clocks will not remain synchronized even in the limit as their velocity relative to the rocket approaches zero? It's not too hard to prove this using the relativistic formulas for time dilation and velocity addition.

 

[Dale]

This still doesn't explain the relation between, the one way speed of light, slow transport and an experimental action.

As far as I could understand, the question wasn't about slow transport, but I am glad to discuss it now that you have clarified your intention.

Slow transport synchronization is equivalent to the Einstein synchronization convention. So, in an inertial reference frame (which by definition uses the Einstein synchronization convention) we determine that slowly-transported clocks maintain their synchronization. However, if we were to use another synchronization convention then slowly transported clocks would not remain synchronized. Here is an example:

Suppose that we have a lab with three clocks. Clock A and clock B are separated by a distance of 5 feet and are synchronized by the Einstein synchronization convention, so if A emits a pulse at t = 0 ns, then B receives the pulse at t = 5 ns, and the reflection returns back to A at t = 10 ns. The one way speed of light is c = 1 ft/ns in both directions. Clock C is initially at rest next to A and is synchronized with A. It is then slowly transported to B and found to be synchronized with B.

Now, instead suppose that A and B are synchronized by "everyday" synchronization where B simply sets its clock to match the signal that it is currently receiving from A. Using this synchronization convention if A emits a pulse at t = 0 ns, then B receives the pulse at t = 0 ns, and the reflection returns back to A at t = 10 ns. The "outward" speed of light is infinite, and the "inward" speed of light is 0.5 ft/ns. Clock C is initially at rest next to A and is synchronized with A. It is then slowly transported to B and found to be 5 ns ahead of B.

So, the synchronization convention determines the one way speed of light and the effect of slow clock transport. Slow clock transport is equivalent to the Einstein synchronization convention.

The moving frame, is a jet flying a device. The Stationary is the on-ground station with the same device.

Careful, the frame is not a physical object, it is a mathematical object. It is a mistake to identify the frame with the jet or the ground. The "moving" frame is a coordinate system where the jet is stationary, and the "stationary" frame is a coordinate system where the ground is stationary.

One theory will claim that, because of the affect of slow transport mechanism of separating the clocks, no matter how slow, the on-ground clock will measure the speed of light as X and the jet device measures the speed of light differently, say as Y.

The other theory will claim that the slow transport mechanism, doesn't change the measurements results in comparison between the two frames, exactly because the separation of the two clocks, is done slowly, and that both on-ground and jet devices, will measure the speed of light to be the same, let it be X and X or Y and Y or Z and Z.

Which two theories are you discussing here? Assuming that all the frames are inertial then they will all measure the speed of light to be c.

 

[roineust]

OK,
Here is the way I understand things, logically, up to this point.

If there is no way to indicate a logic error, regarding an SR scenario analysis, please try to explain to me why. On the other hand, if it is possible, please try to explain where, and what, is the error, in this presented situation.

I see only two possibilities, that will be described shortly. Although, it seems that most of the comments in this thread, indicate towards only one possibility, it seems, somewhat, still a fuzzy choice, and not a clear cut, so I treat the outcome of both possibilities.

This fuzziness in my understanding, of what is the true possibility, in my opinion, arises from the almost immediate operation, commonly done while analyzing SR scenarios, of 'looking at the situations from other points of views, or frames' – I am interested in this post here, to look at things, only from within the 'moving' frame.

So- either the A and B clocks, after separated by slow transport, are considered, as seen from within the moving frame, as synchronized, or they are considered, not synchronized. I don’t see any more possibilities. It seems that most of the comments, if not all of them, agree that they stay synchronized, as seen from within the moving frame, after a slow transport. But again, as explained, I will relate to both possibilities.

Possibility no.1: A & B clocks stay synchronized.
In this case, as much as I understand, we are back to the previous spot. We are left with no more ways to explain, why the situation, as depicted in the moving frame, in diagram no.1 - is NOT a true depiction.

Possibility no.2: A & B clocks are NOT synchronized.
In this case, please look at attached diagram no.2 – If the slow transport actually does de-synchronize A & B clocks, as seen from within the moving frame, then:

The difference of time measurement, indicated by clocks A & B, in diagram no.2, can not be explained, only by the horizontal distance difference R, that light travels between clocks, but also has to be explained, as a combination of both distance difference R that light travels, and a result of a previous slow transport de-synchronization.

Conclusion:
If we started from the assumption, that it is not possible, that the clocks A & B are both synchronized and De-synchronized at the same time, as seen ONLY from within the moving frame – But that only one possibility is true, then:

Possibilities 1 & 2 can not both be right, and can not both be wrong.
Either one is wrong, while the other is right, or vise versa.


So, which possibility is correct, or where is my error here?


Thanks,
Roi.

 

[harrylin]

OK,
Here is the way I understand things, logically, up to this point.

If there is no way to indicate a logic error, regarding an SR scenario analysis, please try to explain to me why. On the other hand, if it is possible, please try to explain where, and what, is the error, in this presented situation.

I see only two possibilities, that will be described shortly. Although, it seems that most of the comments in this thread, indicate towards only one possibility, it seems, somewhat, still a fuzzy choice, and not a clear cut, so I treat the outcome of both possibilities.

This fuzziness in my understanding, of what is the true possibility, in my opinion, arises from the almost immediate operation, commonly done while analyzing SR scenarios, of 'looking at the situations from other points of views, or frames' – I am interested in this post here, to look at things, only from within the 'moving' frame.
[..]

That's ambiguous - for "only from within the 'moving' frame", the view is that everything is in rest.
If you meant that (which I doubt), for sure you already know the answer of what will be measured in rest!

Perhaps you want to look at how things will be measured with the moving frame, as determined with the rest frame? In that case you must distinguish between "are" (=according to rest frame A) and "measured as" (=according to moving frame B).

As long as it is not clear what you mean, no answer can be given to your questions.

Harald

 

[Dale]

I am interested in this post here, to look at things, only from within the 'moving' frame.

I assume by "the moving frame" you mean the frame in which the apparatus is moving. If you mean the frame in which the apparatus is stationary please let me know.

So- either the A and B clocks, after separated by slow transport, are considered, as seen from within the moving frame, as synchronized, or they are considered, not synchronized.

They are not synchronized, but technically it is impossible to do slow transport of the clocks in the frame in which the apparatus is moving. The clocks only remain synchronized in the frame in which they are moving at an infinitessimal speed (slow transport). In other frames where they are moving at finite speed (not slow transport) they do not remain synchronized. Whether or not the clocks are transported slowly is a frame-dependent concept, just like speed and synchronization.

Possibility no.2: A & B clocks are NOT synchronized.
In this case, please look at attached diagram no.2 – If the slow transport actually does de-synchronize A & B clocks, as seen from within the moving frame, then:

The difference of time measurement, indicated by clocks A & B, in diagram no.2, can not be explained, only by the horizontal distance difference R, that light travels between clocks, but also has to be explained, as a combination of both distance difference R that light travels, and a result of a previous slow transport de-synchronization.

Yes, both effects are present and exactly counteract each other. Thus, if they are detected as simultaneous in one frame they are detected as simultaneous in all frames.

At this point I think that you really need to actually work this problem out quantitatively using the Lorentz transform. You are just confusing yourself verbally and need to work through the math in order to gain some clarity.