Tutorial: Relativity of simultaneity

[Quantum Quack]

How do you go from "rate of movement has increased" to "thus time has slowed"?


Seems completely illogical to me.

A greater distance is covered in a given amount of time, if you were an observer abaord a water molecule would time not appear to be slower?

What do you mean by "atomic rate", exactly? And why would it slow down in the way you say? And why do different atoms all seem to slow by the same amount? And why does the slowing appear to be frame-dependent?

Inertia.

Simultaneous means occurring at the same time. There's no special meaning to the term "simultaneous".

so tell me what isn't occuring in the same moment?

If you're interested in the relativity of simultaneity, please see the thread I started on that very topic.

This is the very thread you refer to.....in case you hadn't realised

The relativity of simultaneity is a derived consequence of the postulates of special relativity, which hardly makes it a way of avoiding "solid argument". It isn't introduced ad hoc. It's a consequence of the theory.

well lets have the nitty gritty, No point just claiming non-simultaneosness with out quantifying it...like how far into the past are the events you refer to?

If you want to discuss it, please see my thread titled "Tutorial: Relativity of simultaneity"

This is the very thread you refer to.....in case you hadn't realised

Am starting to think your posts are coming from a robot

What is "the NOW"?

If you don't know what the NOW is I suggest you look at your watch and tell me when you record events or even record the duration of events. From NOW to NOW type thing......

JamesR obviously you are avoiding answerring my questions about the time diagrams I have been posting...can I ask why?

You mean to tell me that you can not see the meaning of this diagram?

If you can't see the simple logic that is shown then obviously I am asking the wrong person questions about simultaneousness and non-simultaneousness.

 

[Quantum Quack]

Just thinking more about my response about asking "what doesn't occur at the same moment?"
[just realised that the so called simple diagram is harder to comprehend than I first thought]

If a meter and a meter are 100mm and 90 mm due to length contractions are they the same length?
If an event happens at another time due to time dilation and length contraction are they the same event?

They are obviously the same event so the event does happen simultaneously. If I am travelling in a dimension that is larger by a factor of 0.4 but both dimensions fill the same volume are the dimensions the same over all size?

I would argue that the event is simultaneous even if that event is arrived at by differring spacetime dimensions.
Thus the pole in the barn is the same event but viewed differently due to dimensional perspectives.

Now you will probably claim that I am taking a global view from some absolute POV. Well I guess I am. But in my defence there is always only one event even if thought of as non-simultaneous. Just because the tick rates and distances are different does not mean there is more than one event. And that event is simultaneous for both frames even though it is recorded with differing time and distance dimensions.

Sorry if I have confused

 

[Quantum Quack]

it's a bit like the famous Tardus in the old Sci Fi series Doctor Who. Where by the inner dimensions of the telephone box are considerably larger than the outside dimensions. Yet those dimensions co-exist.

 

[geistkiesel]

"Geist just to fuel the theoretical fire, Lights effects might be invariant but that doesn't mean that light has velocity to screw the figures with."

From my point of view QQ, I am considering the photons in motion, even though I have never actually seen a photon in motion, now that you mention it.

And how do you do the animations anyway voodoo perhaps? You know it isn't fair that only an elite few of us enjoy the privelege of animatedness in their posts. It just isn't fair.
Geistkiesel​

 

[Quantum Quack]

well it is a point of interest to note that no one has seen a photon in transit. It is only the effect of light that we actually observe.

As a non-physicist I find it amazing that we have declared an object has velocity and yet never proved that it actually has. I guess you have to identify the "it" to do it.

The same could be said for a magnetic field or other EM.

The effect is obvious and very measurable but can it be identified as an entity? I don't think so ......if the field is an artifact of polarised space time then magnetism and EM can only be identified in those terms.

 

[Quantum Quack]

From my point of view QQ, I am considering the photons in motion, even though I have never actually seen a photon in motion, now that you mention it.

And how do you do the animations anyway voodoo perhaps? You know it isn't fair that only an elite few of us enjoy the privelege of animatedness in their posts. It just isn't fair.
Geistkiesel​

I we consider even in abstract that the effect of light is the realisation of a vacuum potential at a given object rather than a projectile with velocity we have a much simpler view of the universe and a way of understanding gravity.

Sorry about you not seeing the animations.

 

[geistkiesel]

I we consider even in abstract that the effect of light is the realisation of a vacuum potential at a given object rather than a projectile with velocity we have a much simpler view of the universe and a way of understanding gravity.

Sorry about you not seeing the animations.

QQ,
I saw the animations, I want to know how you do them.
Geistkiesel

 

[Quantum Quack]

QQ,
I saw the animations, I want to know how you do them.
Geistkiesel

theres free gif animation software available at :
http://www.freeserifsoftware.com/default.asp

DrawPlus is quite good.... Superluminal put us onto it.....

 

[Quantum Quack]

BTW the Draw plus software is about 20 mb and the animations are quite simple to put together.......

 

[geistkiesel]

Geist, do you believe that Earth's reference frame is the universal reference frame? That earth is at absolute rest? If so, then which of Earth's many different reference frames is it, because we go around the sun and six months later, we will be traveling the opposite direction wrt the sun.

No, I do not believe that the earth is siitting in a state of absolute velocity = zero rest. I say that in the measurement of light the motion of the earth does not insert errors that cannot be determined and therefore removed.

Assume thesun is dragging the solar syustem aking with it at 208 km/sec. Further, that the earths spin axis isa aliogned along the sun diretion of motion and thjagt the rotational and orbital velocity of the earth is effectvely orthogonal to thesun motion. Caqlcul;ate the instantaneous veloctyy vectores for the three states and sum them toi the total motion vector and see what you get. Your example indicates to me that you have never done this calculations and that you probably do not know how to do it despite the reality it is crucial to what you described in your post to me.

You apparently haven't read Dayton Miller's paper regarding his measurements re he MM experiments.

Here is a link to Miller 101

Look at it like this. Virtually every inertial frame Vf that moves wrt the embankment, the earth, has accelerated wrt the embankment, Ve. The Ve has never been observed to accelerate in the sense that Vf acclerates and produces a relative motion wrt Vf and Ve. Here, however, we know apriori, that it was the Vf that accelerated, not the Ve, therefore why pretend the silliness of asuming the Vf is at rest wrt Ve just because you can move your pencil ver the surface of a piece of paper and crunch out the 'theory' that the Vf, say a passenger train, could, once a relative motion wrt Ve is observed ever, be at rest and the Ve be moving wioth relative velocity VF (whioch must be the emasured relative velocity. This is physically impossible condition to achieve, and all the theory in the universe is not going to change that reality.
The frames are not equivalent. Ve and Vf, that is. Only Vf accelerates with reaspect to Ve and you cannot come back a week after the acceleration event and say, I've frgoptten I have moved so I'll just assume SRT as the fix fopr the lapsed mermory.

Finallhy, those SRTs that make the challenging statement that those like myself who are thinking intuitively and seeing the results through a rational model are erroneous, or old fashioned try to intimidate confessions by the manner of their speech. I ask that these kinds of people please leave me alone.

SRT can preach the mantra that the relative velocity of frame and photon will always ,easure C is sheer nonsense. Tio assume this universally is to ignmore even the possibility of , or need to measure the relative velocity of frame and photon. This says that never in the development of human technology will there be a possibility to do what is claimed to be impossible. Whatever, AE was using to justify his assumption has never been proved to my eyes to satisfy the requirements of proof. Not the ecllipse experiments, not the MM experiments, none of the experiments do this. I do not remember the details of the argument I saw in one of your first posts but you jumped right in with expressed belief of a commited pilgrim that the relative velocity of frame and photon will always be measured at C and hence thedebate was iover and yo0u walked away thinking you's won. You held it out to the forum as a "proof". I was bored. I have been hearing this and analyzing this for a long time and have never been impressed.

You should check out your method. Here you ask a question which I denied but you continue with the question before I answer it.

You have never, like all SRTists, been able to respond to criticisms of SRT based on the merits of the presented argument. This is not a challenge to your character, or your knowledge of physics.

Look at the figure again if you haven't examined it carefully. Tell us where the error is if you disagree with the obvious conclusions. No one has been able to this yuet, hyet those failing still scorn, go figure.

Remember, the invariant location of the emission point of the photons. Look at the reality that indeed the light is in motion, just like any other object moving uniformly. Look at the motion of the light as completely uncaring what all the observation is around the photon motion.

Are you able to prove with certainty that the photons will arrive at L and R simultaneously? Prove it I mean. Don't ask me what I
believe, look at the problem and solve it. You are unable to do so without draggng cliched formulae from off the shelf.

First, if you use the "consideration" of the moving observer as a crucial condition in your conslusion you have failed. The photons care not of what is considered. Even if you do use the "consideration" of the observer your use of his observations are trivially simple to negate. If you do not believe me then take this on. Run it to its natural conclusion. However. you are not going to make a lot of points uising some Socratic methodology, of leading me, or any else familiar with SRT, down a path of which you may think we are ignorant.

In the experiment in the figure all time measurements are wrt the moving clocks. There is symmetry in the ML and MR distances M being the midpoint of the L and R clocks. See if you can follow the logic of the development of the t' expression.

ASk yourself just one question. When the left photon has moved ct and arrived at L the right photon has moved an equal distance has it not? I am not asking about any frame motion here.

When thje left photon then reflects back to the emission point it has travelled another ct distance right? ALso the right photon has travelled ct. But the photons do not arrive at the L and R clocks at the same time because the fucking frame id moving.

I am not saying absorbed what I say is the truth, I say just analyze the problem wrt the photon motion motion.

.

Assume the experiment has been run 10,000 times using the same relative velocity every time. Then the stationary observers can place clocks exactly at the locations of the L and R clocks when/where the photons arrive, correct? We can get the same results using stationary clocks even, but the difficulty you have is to argue away that two clocks colocated, one moving, the other stationary, (really stationary) will not record the arrival of the photons at the colocated positions simultaneously.
Go for it.

Geistrkiesel [/'indent]

 

[Sabejias]

You seem to be suggesting my view. That is we should refer to "Clock Dilation" and not "Time Dilation".

That is external energy inputs to the clock causes it's process to change hence marking the time interval at a different frequency but with no actual change in time perse.

It is simular to the affect of the batteries getting low in my timex.

Is this part of your method of telling that you are moving. If there is no reciprocity, and a light clock works like a wristwatch, then in six months, you will notice that suddenly, the light clock is ticking slower than the wristwathc assuming that the battery does not deteriorate too much. TIME DILATION is not caused by batteries running low.

 

[funkstar]

Hi there.

If you don't know what the NOW is I suggest you look at your watch and tell me when you record events or even record the duration of events. From NOW to NOW type thing......

Well, what does your animation illustrate? If I understand it correctly, you seem to want to show the progression of time of one FOR relative to another FOR, correct?

In that case case the NOW marker would be nothing more than a transform telling us how to change from time in one FOR to another.

And therefore, that there is a sort of singular universal state, even though the time might progress differently in different FORs, right? It seems to be illustrating that when t = 4 in one frame then t' = 6 in the other, for instance, and that there is one universal state at those times, even though the passing of time has different rates in different FORs.


If this is not what you mean, then please disregard the rest of my post. Otherwise, let us return to the original experiment, and assume that your view is true.

In the rod frame, the clocks read the same time for the light to reach L and R (as they must by the assumption of light speed invariance in spite of frame). Now, by the simple NOW-transform, light must also reach L and R at the same time in the rest frame (it might not be at the same reading of time, but nonetheless, they should be simultaneous), correct? The state is consistent, though the timing may vary.

This is (unfortunately) a false way to view it, and we can show this by looking at the experiment from the rest frame, as did James R in the first post, and show that from there (again due to the invariance of speed of light in a reference frame), the light does indeed not hit L and R at the same time. The state of the universe is not consistent across the NOW-transform.

In other words, NOW-transform directly contradicts the light speed invariance assumption. Of those two, I would dismiss the idea of a universal NOW (which is just universal time in light disguise). It would be lovely if the universe was Newtonian, but the nice flat view of space (and time) we carry around in our heads and use everyday to great effect, just isn't true. It seems counterintuitive because at those scales of magnitude our brains are adapted to, it is a very, very good approximation, but outside of those magnitudes, our "natural" view of the universe is not applicable.

 

[Neddy Bate]

You apparently haven't read Dayton Miller's paper regarding his measurements re he MM experiments.

Here is a link to Miller 101

IF Miller's results are systematically caused by absolute motion of the apperatus through space/aether (and that is a big IF) then physicists should discard relativity theory and return to Gallilean/Newtonian principles. Then they should work out a new model to explain the relativity-like effects they have observed, such as time dilation. They would also owe some gratitude to Miller and a few on this forum for helping them realize their error.

Look at the figure again if you haven't examined it carefully. Tell us where the error is if you disagree with the obvious conclusions. No one has been able to this yuet, hyet those failing still scorn, go figure.

Remember, the invariant location of the emission point of the photons. Look at the reality that indeed the light is in motion, just like any other object moving uniformly. Look at the motion of the light as completely uncaring what all the observation is around the photon motion.

Believe me, I have been tempted to discard relativity many times during my ongoing attempt to understand it. As recently as yesterday I was so baffled by a relativity paradox that I was finally going to give up. Then, after a little math and a diagram or two, (thanks to Quantum Quack for one of his animations) the paradox finally went away. I predicted that it had to be my understanding that was in error, and not the theory itself, and that did turn out to be the case.

If we forget about relativity theory, and look at the scenario with a fresh perspective, it is tempting to believe that Gallilean/Newtonian principles are sufficient. It would be natural to believe that your system is a valid test for absolute motion.

The first experiment we would do is to measure light as moving at c+v in one direction and c-v in the opposite direction. I now realize that you do not make the mistake of believing that light information can propgate faster than c, you simply have the receiver-clock moving toward the light and closing the distance, similar to a linear Sagnac effect.

I apologize if I am oversimplifying your concept, or if I am missing your point entirely. I have been thinking about relativity so much lately that I might have forgotten how to look at things intuitively.

 

[funkstar]

No, I do not believe that the earth is siitting in a state of absolute velocity = zero rest. I say that in the measurement of light the motion of the earth does not insert errors that cannot be determined and therefore removed.

Sorry? Are you denying or affirming the invariance of c? Because if there are no error to be determined...

Assume thesun is dragging the solar syustem aking with it at 208 km/sec.

With respect to what?

Look at it like this. Virtually every inertial frame Vf that moves wrt the embankment, the earth, has accelerated wrt the embankment, Ve.

But where is the embankment? Is that at rest?

The Ve has never been observed to accelerate in the sense that Vf acclerates and produces a relative motion wrt Vf and Ve. Here, however, we know apriori, that it was the Vf that accelerated, not the Ve, therefore why pretend the silliness of asuming the Vf is at rest wrt Ve

I don't think anybody is claming that. Relative rest is rather dull.

just because you can move your pencil ver the surface of a piece of paper and crunch out the 'theory' that the Vf, say a passenger train, could, once a relative motion wrt Ve is observed ever, be at rest and the Ve be moving wioth relative velocity VF (whioch must be the emasured relative velocity. This is physically impossible condition to achieve, and all the theory in the universe is not going to change that reality.
The frames are not equivalent. Ve and Vf, that is. Only Vf accelerates with reaspect to Ve and you cannot come back a week after the acceleration event and say, I've frgoptten I have moved so I'll just assume SRT as the fix fopr the lapsed mermory.

Ok. Then where is the primordial embankment?

SRT can preach the mantra that the relative velocity of frame and photon will always ,easure C is sheer nonsense.

Ah, denying it. Then the onus is on you to find, say, a sub- or superluminal photon in a vacuum. And an explanation for gravitational lensing. Oh, and explain why relativistic effects need to be accounted for in GPS. And find the absolute rest frame. And an explanation for the precession of the perihelion of Mercury. And an explanation for the frame dragging effects recently confirmed. And explain why those atomic clocks don't match up.

Common sense does not override reality.

Tio assume this universally is to ignmore even the possibility of , or need to measure the relative velocity of frame and photon. This says that never in the development of human technology will there be a possibility to do what is claimed to be impossible.

Measuring the velocity of the frame and a photon is easy.

...the relative velocity of frame and photon will always be measured at C...

The frame at c relative to some rest frame?!?

Remember, the invariant location of the emission point of the photons.

This is just another way of saying "absolute space and time".

Are you able to prove with certainty that the photons will arrive at L and R simultaneously? Prove it I mean. Don't ask me what I believe, look at the problem and solve it. You are unable to do so without draggng cliched formulae from off the shelf.

First, if you use the "consideration" of the moving observer as a crucial condition in your conslusion you have failed.

In other words, if we don't accept absolute space and time we have failed. Sorry, no-can-do.

James R's analysis, given the invariance of light speed, is perfectly correct: The rod clocks will show the same time when the photons hit. You may not believe that this is true for the real universe, but the thought example is unassailable.

In the experiment in the figure all time measurements are wrt the moving clocks.

Sure, if space and time are absolute, and the point of emission is at rest (meaning fixed) in this frame.

There is symmetry in the ML and MR distances M being the midpoint of the L and R clocks. See if you can follow the logic of the development of the t' expression.

ASk yourself just one question. When the left photon has moved ct and arrived at L the right photon has moved an equal distance has it not? I am not asking about any frame motion here.

When thje left photon then reflects back to the emission point it has travelled another ct distance right? ALso the right photon has travelled ct. But the photons do not arrive at the L and R clocks at the same time because the fucking frame id moving.

I am not saying absorbed what I say is the truth, I say just analyze the problem wrt the photon motion motion.

All this, with except for the moving clocks reading different times, is largely what the stationary observer sees.

Assume the experiment has been run 10,000 times using the same relative velocity every time. Then the stationary observers can place clocks exactly at the locations of the L and R clocks when/where the photons arrive, correct? We can get the same results using stationary clocks even, but the difficulty you have is to argue away that two clocks colocated, one moving, the other stationary, (really stationary) will not record the arrival of the photons at the colocated positions simultaneously.
Go for it.

Geistrkiesel [/'indent]

If time and space are absolute, then, of course, you're right. If you want us to show relativistic effects in a Newtonian universe, then, of course, we can't.

But this universe does not appear to be Newtonian.

 

[Quantum Quack]

Hi there.


Well, what does your animation illustrate? If I understand it correctly, you seem to want to show the progression of time of one FOR relative to another FOR, correct?

In that case case the NOW marker would be nothing more than a transform telling us how to change from time in one FOR to another.

And therefore, that there is a sort of singular universal state, even though the time might progress differently in different FORs, right? It seems to be illustrating that when t = 4 in one frame then t' = 6 in the other, for instance, and that there is one universal state at those times, even though the passing of time has different rates in different FORs.


If this is not what you mean, then please disregard the rest of my post. Otherwise, let us return to the original experiment, and assume that your view is true.

In the rod frame, the clocks read the same time for the light to reach L and R (as they must by the assumption of light speed invariance in spite of frame). Now, by the simple NOW-transform, light must also reach L and R at the same time in the rest frame (it might not be at the same reading of time, but nonetheless, they should be simultaneous), correct? The state is consistent, though the timing may vary.

This is (unfortunately) a false way to view it, and we can show this by looking at the experiment from the rest frame, as did James R in the first post, and show that from there (again due to the invariance of speed of light in a reference frame), the light does indeed not hit L and R at the same time. The state of the universe is not consistent across the NOW-transform.

In other words, NOW-transform directly contradicts the light speed invariance assumption. Of those two, I would dismiss the idea of a universal NOW (which is just universal time in light disguise). It would be lovely if the universe was Newtonian, but the nice flat view of space (and time) we carry around in our heads and use everyday to great effect, just isn't true. It seems counterintuitive because at those scales of magnitude our brains are adapted to, it is a very, very good approximation, but outside of those magnitudes, our "natural" view of the universe is not applicable.

Thanks for your post Funkstar, [welcome to sciforums] and yes you have understood the diagram as a simple transform between frames.

The interesting thing is that this view of non-simultaneousness leads one to ask:

If a collision happens in one frame does the colision happen in another?
Obviously it seems to me that if we are talking about a single colision of photons event then this seems to be impossible according to SRT to have this event occur in both relative frames. Thus a unchanged photon goes onto have a future in one frame but is changed in another. That according to the photon there isn't invariance but acording to an obsever of that photon there is invariance.

 

[James R]

QQ:

My apologies for referring (twice) to this thread, when I was actually posting in it. For some reason, I obviously didn't realise this was that thread. I guess it's a case of having too many browser windows open at once, and mixing them up.

A greater distance is covered in a given amount of time, if you were an observer abaord a water molecule would time not appear to be slower?

No. It would appear you were going faster. Wouldn't it?

Inertia.

Inertial makes time appear to go slower? How?

so tell me what isn't occuring in the same moment?

Huh?

well lets have the nitty gritty, No point just claiming non-simultaneosness with out quantifying it...like how far into the past are the events you refer to?

See my first post. All the math is there.

If you don't know what the NOW is I suggest you look at your watch and tell me when you record events or even record the duration of events. From NOW to NOW type thing......

So "now" is just every time an observer looks at his watch. There's nothing special about that.

JamesR obviously you are avoiding answerring my questions about the time diagrams I have been posting...can I ask why?

You mean to tell me that you can not see the meaning of this diagram?

Your "NOW" is not shared between reference frames. If the observer in one frame says an event is happening "NOW" at some given time coordinate, then an observer in the other frame will give the same event a different time coordinate and call it "NOW".

If your idea is that "NOW" is a particular event, which every observer sees occur at some time or other, then you're right. All observers eventually see all events. But they see them at different times. That's the whole point.

Your diagram seems to imply that you can sit outside the two time streams and watch the universal "NOW" move along. You can't. All observers are in time. None are outside it. The "NOW" moves at different rates for each observer.

 

[Quantum Quack]

JamesR , Thanks for your response I see the situation much more clearly now given yours and funkstars posts.

 

[Quantum Quack]

Just trying to find a way to clarify the issue with this diagram [not- animated]

In A's frame the target [A2] is hit simultaneously by both beams of light.

The Question is:
In Ship B's frame [v=0.8c] do the beams of light hit the target [A2] simultaneously?

 

[geistkiesel]

IF Miller's results are systematically caused by absolute motion of the apparatus through space/aether (and that is a big IF) then physicists should discard relativity theory and return to Gallilean/Newtonian principles. Then they should work out a new model to explain the relativity-like effects they have observed, such as time dilation. They would also owe some gratitude to Miller and a few on this forum for helping them realize their error.

Neddy, if you are ever in Bullhead Cit Az, give me ring and I will show you a very interesting town. Just accross the Colorado River is Laughlin, Nevada, an eight Casino size town of really fun sin.

Believe me, I have been tempted to discard relativity many times during my ongoing attempt to understand it. As recently as yesterday I was so baffled by a relativity paradox that I was finally going to give up. Then, after a little math and a diagram or two, (thanks to Quantum Quack for one of his animations) the paradox finally went away. I predicted that it had to be my understanding that was in error, and not the theory itself, and that did turn out to be the case.

Many years ago I was at a seminar where a new hired prof in the physics department (PhD Cal.Tech), was giving a lecture "proving" that accelerastion had no SR affect. I was following along nicely, until I realized that it wasn't physical limitation of acceleration, it was just that there wasn't any room for it, at least that was my understanding. The speaker couldn't do anything but cite theory and then a miracle happened. Another staff prof, was engaged in a spirited discussion with the SR speaker and he uttered the words, "but Idon't accept special and general relativity" . I was impressed..Hey, I thought for all the"social pressure" to at least pay lip service the rule wasn't absolute.

Associated with acepting SRT there was only one dissident prof. He didn't seem uncomfortable beng the only one in the room objecting point for point in the discussion. Finally I saw trhe speaker fading, but not from losing logic battles, he was just worn down by a more experienced and practiced physicist.

If we forget about relativity theory, and look at the scenario with a fresh perspective, it is tempting to believe that Gallilean/Newtonian principles are sufficient. It would be natural to believe that your system is a valid test for absolute motion.

It sure seems valid to ne. Neddy, get a copy of David Bohm's TheTheory iof Relativity" He describes a gedanken with a moving frame and a couple of photons and a SRT predictable result. I did a similar analysis on that experiment usinmg the same basis approach used here. Do like you said for a couple of hours. Forget theory, you wont be corrupted..

The first experiment we would do is to measure light as moving at c+v in one direction and c-v in the opposite direction. I now realize that you do not make the mistake of believing that light information can propgate faster than c, you simply have the receiver-clock moving toward the light and closing the distance, similar to a linear Sagnac effect.

It sounds about right. I am not versed in Sagnac enough to comment ratonally, but it sounded right the wqy you stated it.

I apologize if I am oversimplifying your concept, or if I am missing your point entirely. I have been thinking about relativity so much lately that I might have forgotten how to look at things intuitively.

No apologies neccessary, even if yiou did over step which you didn't. I have recently been dioscussing just what limitiations there are on what the observers can actually see, or "consider" in invoking SR. For the current problem, let us take all information from the moving observer.The only data we show him is what he would be seeing in any event.

First he sees and records the time of emission the photons emitted in the two directions. Now the next event he observes, being located at the physical midpoint of the frame, is the simultaneous return of the photons to the midpoint. What data has he? He has the emission time and the return time and therefore the round trip time. He also has the arrival time of the photons at L and R embedded in the return signal. So now he has the time of arrival of the photons at L and R. he knows the photons were emitted and if the signal had been coded in some appropriate manner way before the light was emitted he could deduce with a the high probability of success that the emitted and return photons were the same.


Now he is told the L and R clocks are located at equal distances from the physical midpoint. Now the data, also collected on the stationry frame with clocks colocated with L and R. These stationary clocks also have provided the moving obseve with th e arrival times. Let us for thrills also give the moving observer data for a test with the frame at rest wrt the embankment, Ve. What can the observer do/say with the data? Hold the last bit of information from the observe at first. Can the observer deduce the postulates of SRT from this experiment?

I think not. What about the postulate that insists that the moving observer will always measure the speed of light as C? Actuallthe postulate refers tot he measurment of the realtive velocity of frame and pholton, bhut using relative velocioty one must at some tiem say all relatibve velocities are emasured wrt the inwertial frames withe exception of the relative motion of frame and photon. If he conducts an anlysis as I have done above he will not necessaruly come to an SRT result.

Where has the observer actually measured the speed of light here?

Hhe knows the distance d = LM=RM. He learns the arrival time oaftyer trfavlelng ct = d - vt for the left photon. or t = d/(c + v). And the right moving photon what does he determine about this?. That the frame moving vt to the right places the right photon at 2vt from the right moving photon that has also moved distance of vt and the right photon is now 2vt from R and he ends up with a classic Geitkiesel result. If we now show him staionary frame data there is a difference of t' from the round trip travels of the photons in the stationary frame.

LEt us see how SRT could slip into the results from the data at hand. Can the observer construct any rational model duplicating an observation that the relative velocity of frame and photon will insist that both photons will measure the same relative velocity of frame and photon for the two cases?
From the data the answer is definitely no. So what compelling reason would the observer have in assuming that the relative velocity of frame and photon are identical, when all the data says the frame was moving wrt Ve?

Now the observer really focuses in on the stationary data and discovers the photon data arrival at L and R simultaneously and that the light took t = d/c to arrive at both L and R in the stationary frame and that compared to the time of arrival of t = d/(c + v) in the moving frame which is less than the time in the stationary case . Further, the full distance travelled by the right photon in reaching R is ct + ct' or ct + 2vt + vt'.. D = t (2v + 1)= t (2v + 1) + vt ';time of arrival of the R photon at R is determiend from ct + c t'
The observer must conclude the frame is in motion wrt the embankment.


Geistkiesel​

 

[James R]

QQ:

The interesting thing is that this view of non-simultaneousness leads one to ask:

If a collision happens in one frame does the colision happen in another?

Yes. All EVENTS happen in all frames. If I eat a sausage in one frame, then I eat it in all frames. Anybody watching me sees me eat it, at some time or other.

Events are absolute. Everybody agrees on WHICH events happen. They just don't agree on WHERE and WHEN they happen.