Problem with relativity of simultaneity original example

[Adel Makram]

I did comment: It's irrelevant to Einstein's thought experiment. No one's getting 'fooled'; simultaneity is frame-dependent.

1) The external observer can not make this statement without a M`-observer. If he can, it would be enough just A` and B` for him to reach the same conclusion
2) The relativity of Simultaneity based on the Einstein`s Thought Experiment is a personal speculation of the external observer, not a real principle of physics

 

[JDoolin]

This raises up a conclusion that any sort of Transformation between the 2 FORs should be asymmetrical. And because the well known Lorentz T (LT) is symmetrical one, this means that LT is not true

I don't think the Lorentz Transformation is "symmetrical" in the sense you are describing.

If you have two trains passing each other in opposite directions.

What are really simultaneous events on one train will appear to happen in consecutive order, back to front, from the other train.

What appears to happen simultaneous from the other train, is really happening in consecutive order from front to back from the same train.

(Edit: Caveats, Clarifications, Qualifications: I say "what is really happening" when I mean, watching events happen on your own train, whereas I say "what appears to happen" when describing events that happen on the other train. Of course, "what appears to happen on the other train" is still "really" happening, but I hope you can understand the gist. This also doesn't take into account any effects of the delay caused by the speed of light, so when I say "what appears to happen" that is after you've accounted for any speed-of-light-delay-effects, and calculating the object where it "was" when the light left it, not how it actually appears, which is the way this thought experiment is usually done.)

 

[Doc Al]

1) The external observer can not make this statement without a M`-observer. If he can, it would be enough just A` and B` for him to reach the same conclusion

You miss the point of the thought experiment. The purpose of using M' is just to make it easy to analyze the scenario. But the fact that A' and B' are hit by lightning at different times according to their clocks does not depend on having an observer at M'. All you have to agree upon is that the light flashes reach the middle of the train at different times. This is a simple fact agreed upon by all.

2) The relativity of Simultaneity based on the Einstein`s Thought Experiment is a personal speculation of the external observer, not a real principle of physics

Nonsense.

Please reread my comments at the bottom of post #39 before continuing.

 

[Adel Makram]

1) Again, the arrangement made by the external observer of the experiment and his expectation about what A` and B` would observer is different from the arrangement made by the train observer M` if M` conducts the experiment maintaining a time delay between emitting the light toward B` before A` ( in the second situation, the external observer can not be sure that the light from B` and A` would arrive him at the same time)
2) The Einstein thought experiment can not explain the Doppler-Paradox I proposed in comment #47

 

[Adel Makram]

The prediction that the light reaches A` and B` at different time is an indirect assumption made by the external observer. He used the fact that M` knows that light speed is constant and the reflected rays should reach both ends at different times. This is another common sense assumption similar to the pre-relativity common sense that the 2 events happening at the same time should be so for all observers,,, the external observer can`t give any visual evidence based on optics to prove that,,, in fact it might be impossible for him to see A` and B` at the same time and at different time. I also have no idea if there is any computer simulation that can show so,,, If the external observer wants to know whether A` and B` times are different, he should ask them once the lightning struck A` and B`

 

[Adel Makram]

Again, if the external observer considers what M` might see on one hand and what he sees on the other hand, the Doppler-paradox will emerge,,, this is similar to the statement that the external observer considers that M` knows that B` happens before A` and on the other hand sees that A` and B` occurs together at the same time. So the conclusion is: any optical arrangement made to know when M` see A` and B` happen in the train by the external observer will create a paradox, therefore the timing of A` and B` will remains just an assumption unless the external observer ask them directly once they receive the lightning

 

[Doc Al]

The prediction that the light reaches A` and B` at different time is an indirect assumption made by the external observer. He used the fact that M` knows that light speed is constant and the reflected rays should reach both ends at different times. This is another common sense assumption similar to the pre-relativity common sense that the 2 events happening at the same time should be so for all observers,,, the external observer can`t give any visual evidence based on optics to prove that,,, in fact it might be impossible for him to see A` and B` at the same time and at different time. I also have no idea if there is any computer simulation that can show so,,, If the external observer wants to know whether A` and B` times are different, he should ask them once the lightning struck A` and B`

Any observer is perfectly entitled to use accepted physics to predict what the clock readings will be for A' and B' when the lightning struck them. The 'external' observer deduces that the clock readings will be different. And when he contacts those observers later, their measurements will confirm that.

 

[Adel Makram]

I would like to say that assuming a non-simultaneous events in a FOR different from that of the observer is based on common-sense logic. But, if the observer wants to be sure, he should have an objective optical evidence or develops a new thought experiment not based on light transmission alone

 

[Adel Makram]

I have found a semi solution to the Doppler paradox. Regarding the interference pattern part, the light from both ends A` and B` has to reach a middle point in the embankment FOR (M) so as to enter into a slit and then double slit before projecting into screen. Now, The train observer sees the external observer moving from B` to A` direction with a velocity = -v. and when the 2 ends at the embankment received the light from A` and B`, he see that the light fro B` which happens first has to travel a longer distance than from A` to reach the middle of the embankment point. And also the accumulated phase change from B` and A` should be compensated when they reach M. SO the net effect on the screen will be black and bright strips which is the same result as the external observer

 

[Adel Makram]

However, because the train observer will see the lights from A` and B` will be received by embankment observer at the ends of the train as different colour, he can ask them directly about the colour of lights they received. Then, he will found a difference between what he sees as a different colour and what the external observer see as same colour and hence the paradox will emerge again because there is no such way to transform the different colour of lights at B` and A` to the same colour at B and A. This time will be a subjective paradox

 

[JDoolin]

So this "Doppler Paradox" you're describing is the fact that the external observers see different colors than the internal observers?

 

[Adel Makram]

So this "Doppler Paradox" you're describing is the fact that the external observers see different colors than the internal observers?

yes it is

 

[Doc Al]

yes it is

And what makes you think that that is a 'paradox'? (Further, how is it even relevant to the point of the Einstein train example?)

 

[Adel Makram]

Because this time the train observer will consider that the 2 lights will be received by B` and A` as different colours from the start not because he is moving toward the B` end
It is relevant to the thought experiment because the similarity of interpretation. In the Einstein`s one, the train observer will consider that B` and A` times are different from the start too ( same like colours example)

 

[Doc Al]

Because this time the train observer will consider that the 2 lights will be received by B` and A` as different colours from the start not because he is moving toward the B` end
It is relevant to the thought experiment because the similarity of interpretation. In the Einstein`s one, the train observer will consider that B` and A` times are different from the start too ( same like colours example)

Nope, that's all irrelevant. Realize that the events in question are:
(1) Lightning strikes the rear of the train (where A and A' happen to be)
(2) Lightning strikes the front of the train (where B and B' happen to be)

The issue is when do those events occur. We are given that they occur simultaneously according to the track frame (and thus the clocks used by A and B). We use a basic fact agreed to by all that the light reaches the middle of the train (M') at different times to deduce that according to the train frame (and thus the clocks used by A' and B') the lightning strikes occurred at different times. This is just basic physics using the premises of relativity.

 

[JDoolin]

I have found a semi solution to the Doppler paradox. Regarding the interference pattern part, the light from both ends A` and B` has to reach a middle point in the embankment FOR (M) so as to enter into a slit and then double slit before projecting into screen. Now, The train observer sees the external observer moving from B` to A` direction with a velocity = -v. and when the 2 ends at the embankment received the light from A` and B`, he see that the light fro B` which happens first has to travel a longer distance than from A` to reach the middle of the embankment point. And also the accumulated phase change from B` and A` should be compensated when they reach M. SO the net effect on the screen will be black and bright strips which is the same result as the external observer

Part of the problem is you're trying to turn a thought experiment into a laboratory experiment. Not that that is a terrible thing to do, but in this case, we don't have the laboratory equipment necessary to set it up.

The thought experiment asks the question "How is it possible for the external observers to observe the same events as the internal observers, when both see an equal speed of light?" For some time, this question seeme more than a question, but a paradox; an enigma; the sort of question that couldn't possibly have a reasonable answer.

However, as so often happens, once the question is understood, the solution is forthcoming. The solution is to say that those events which appear simultaneous for the internal abservers, happen consecutively, back to front, for the external observers.

That answer is complete, and need not be embellished with further complication.

If you want to add into that set-up bunch of diffraction grating equipment and some fluorescent lights, so that the observers can test for red-shift and blue-shifting of the light, you're free to do so in your thought experiment, but I would agree with Doc Al, that it's irrelevant to the question of simultaneity.

 

[Adel Makram]

I am doing so because I believe that the famous thought experiment only uses limited resources to conclude a general phenomena
Let`s make a new experiment. Let`s make the arrangement so that when A, A` and B, B` coincide, 2 small slits put at B` and A` are opened for a brief time to allow just 2 photons to enter from a source put behind the train ( on the opposite side of the external observer),,, let`s make the distance between the 2 slit small enough comparable to the wave-length of the photons to cause an interference pattern. This brief opening of A` and B` can be done mechanically or even optically
For the external observer, he sees A` and B` open at the same time and therefore the 2 photons entering the 2 slits and create an interference pattern on a screen
But according to Einstein interpretation, the train observer sees B` opens before A` , so B` is opened just for a brief moment and shut before A` opens,,, so at one time, only one slit opens and therefore no interference pattern could ever occur. But when he looks at the screen from his window, he will see an interference pattern on the screen.
Can the train observer now explains why this interference pattern occurs when just the slits open one at a time

 

[Adel Makram]

Part of the problem is you're trying to turn a thought experiment into a laboratory experiment. Not that that is a terrible thing to do, but in this case, we don't have the laboratory equipment necessary to set it up

This is very healthy thing to do not a terrible one as you said. Firstly, I used other thought experiments to disprove the Einstein one. Secondly, if the Einstein` one can stand for many objections but one, it means that it is wrong. Thirdly, I have not problem to refute my own experiments if it is feasible and I did in the Doppler one

 

[Doc Al]

Firstly, I used other thought experiments to disprove the Einstein one.

You did nothing of the kind. Since all you are interested in is 'proving Einstein wrong' it's time to close this thread.

Again I'll quote from the sticky at the top of this forum titled https://www.physicsforums.com/showthread.php?t=17355":

This forum is meant as a place to discuss the Theory of Relativity and is for the benefit of those who wish to learn about or expand their understanding of said theory. It is not meant as a soapbox for those who wish to argue Relativity's validity, or advertise their own personal theories. All future posts of this nature shall either be deleted or moved by the discretion of the Mentors.​