I Time dilation again, Einstein or Resnick?

[PAllen]

In my simulation, the yellow clock's width is half the width of the blue one. If I wouldn't have made that correction, the yellow one would have ticked less than 16 times, so it would have suffered more time dilation than what the data tells us. Without contraction, the muon would simply last longer than expected, and the same would be happening to the clocks on Earth if we would change reference frames.

I have no interest in your simulation. The physics of muons reaching the ground is well eatablished and explained by special relativity. To the extent that you are proposing an alternative personal theory, that is not an allowed discussion topic here and is almost certainly wrong as well.

Also, note in the muon scenario there is no change of reference frames. The muon is inertial for its whole existence, as is the Earth to a reasonable approximation. Any explanation involving change of reference frame is not just wrong but wholly irrelevant.

 

[Raymond Potvin]

I have no interest in your simulation. The physics of muons reaching the ground is well eatablished and explained by special relativity. To the extent that you are proposing an alternative personal theory, that is not an allowed discussion topic here and is almost certainly wrong as well.

Also, note in the muon scenario there is no change of reference frames. The muon is inertial for its whole existence, as is the Earth to a reasonable approximation. Any explanation involving change of reference frame is not just wrong but wholly irrelevant.

My simulation is not off topic, and it is not a personal theory either. It is just a fabulous tool to study relativity. But I admit that I didn't need to rely on the reference frame principle to make it, and I admit that assuming acceleration helps us to determine which clock is moving is not written in the book. Can you tell me why you don't like simulations?

 

[PAllen]

My simulation is not off topic, and it is not a personal theory either. It is just a fabulous tool to study relativity. But I admit that I didn't need to rely on the reference frame principle to make it, and I admit that assuming acceleration helps us to determine which clock is moving is not written in the book. Can you tell me why you don't like simulations?

I didn’t say I don’t like simulations in general. I just see no need to analyze yours for a simple SR problem, and question its value if it keeps leading you to false concepts such as there is an objective distinction as to what clock is moving, and that without this you seem to believe you can’t make predictions. These are horrible misunderstandings.

Besides the muon case, where there is no change of reference frame at all, and no accelaeration, and no meeting of clocks after separating, you should also be aware of the existence twin problems where the amount of acceleration and its profile is the same between twins, but one still ends up younger (what differs between the twins is when, on their own clock, the acceleration is applied).

 

[PeroK]

My simulation is not off topic, and it is not a personal theory either.

You're obviously an intelligent guy, but you should understand that what you believe is not the theory of relativity, but a personal variation based on some aspects of SR and the concept of absolute motion (based on each object retaining a memory of all the accelerations it has ever had).

It's pointless to debunk your theory as I imagine you would not entertain any calculations aimed at that purpose - just as you are oblivious to anyone (including professional physicists) trying to explain that a central tenet of SR is that all motion is relative and that velocity-based time dilation is fully symmetrical.

In any case, you should be under no illusion that you have understood the theory of special relativity. You have not. You have constructed your own alternative personal theory.

 

[Raymond Potvin]

Besides the muon case, where there is no change of reference frame at all, and no accelaeration, and no meeting of clocks after separating, you should also be aware of the existence twin problems where the amount of acceleration and its profile is the same between twins, but one still ends up younger (what differs between the twins is when, on their own clock, the acceleration is applied).

It's so much simpler to add acceleration as an evidence that discriminates the possibilities. A twin cannot say it has accelerated when it has not, that's over complicating the problem for no practical advantage. The muon case is a bit different, but we also know it has been created in the upper atmosphere, that it has been accelerated towards us, and that it has decelerated in the detector.

 

[PeroK]

It's so much simpler to add acceleration as an evidence that discriminates the possibilities. A twin cannot say it has accelerated when it has not, that's over complicating the problem for no practical advantage.

But, despite what you may suppose from the Internet, SR is not just about the twin paradox!

Also, where you are wrong is assuming that using the standard SR approach you either get no prediction or a wrong answer. You have claimed this several times.

In any case, it's still your own variation on SR.

 

[Raymond Potvin]

But, despite what you may suppose from the Internet, SR is not just about the twin paradox!

Also, where you are wrong is assuming that using the standard SR approach you either get no prediction or a wrong answer. You have claimed this several times.

In any case, it's still your own variation on SR.

I claimed that assuming a clock has accelerated doesn't affect the calculations, it only simplifies the understanding. If a prediction can be made while changing reference frames, then the same prediction can be made while only using the rf of the clock that has not accelerated. If no prediction can be made with SR, then no prediction can be made with a simulation either because nothing will help us to know which one of the clocks is moving.

 

[jbriggs444]

I claimed that assuming a clock has accelerated doesn't affect the calculations, it only simplifies the understanding. If a prediction can be made while changing reference frames, then the same prediction can be made while only using the rf of the clock that has not accelerated. If no prediction can be made with SR, then no prediction can be made with a simulation either because nothing will help us to know which one of the clocks is moving.

No experimental results depend on what inertial reference frame you choose to adopt -- i.e. which of the clocks is initially seen as moving.

 

[PeroK]

I claimed that assuming a clock has accelerated doesn't affect the calculations, it only simplifies the understanding. If a prediction can be made while changing reference frames, then the same prediction can be made while only using the rf of the clock that has not accelerated. If no prediction can be made with SR, then no prediction can be made with a simulation either because nothing will help us to know which one of the clocks is moving.

In post #75 I showed you how to solve the problem in a reference frame where both clocks move.

Did you understand that solution?

In any case, the principle of relativity says that you must get the same answer in all inertial reference frames. You do not have to use a reference frame where one clock remains at rest.

Your requirement to know which clock really moves is unnecessary.

 

[Raymond Potvin]

In post #75 I showed you how to solve the problem in a reference frame where both clocks move.
Did you understand that solution?

I said you were right, and I said a simulation would give the same result, but I also said that if we were considering that it is the yellow clock that was accelerating towards the blue one at the end, then we can also consider that it is the one that is accelerating away from it in the beginning, and that the problem was easier to figure out this way.

In any case, the principle of relativity says that you must get the same answer in all inertial reference frames. You do not have to use a reference frame where one clock remains at rest.

Your requirement to know which clock really moves is unnecessary.

It's not necessary if no prediction is necessary, otherwise it is. Without knowing that the yellow clock had to change directions, taking that clock as the rf would not have given the right result because you could have changed the direction of the blue one instead.

 

[jbriggs444]

It's not necessary if no prediction is necessary, otherwise it is. Without knowing that the yellow clock had to change directions, taking that clock as the rf would not have given the right result because you could have changed the direction of the blue one instead.

That only requires knowing which clock changed directions, not knowing which clock (if either) was motionless throughout the exercise.

 

[Raymond Potvin]

That doesn't work in terms of, say, aircraft flying round the Earth. A clock on an aircraft that accelerates and flies West will gain time over a clock that stays at rest at an airport.

That problem is solved using the Sagnac effect, not relativity.

 

[Raymond Potvin]

That only requires knowing which clock changed directions, not knowing which clock (if either) was motionless throughout the exercise.

Assuming that acceleration was not needed for a clock to move around, we could pretend that it is the blue one that moves away and that comes back later, and we would simply get reversed results. We can only make predictions when we know for sure which clock has accelerated.

 

[Herman Trivilino]

It is from the light clock mind experiment that the whole relativity was erected, that the nature of space and time was conceptualized.

Do you have a reference for this claim?

The reason I ask is that I was under the impression that the light clock is a pedagogical tool, used to explain relativity. And by the way, it is not the only way to explain it. Look, for example, at Bondi's k-calculus approach. No light clocks there!

Have you considered the possibility that the muon example and the twin trip example are fundamentally different? Analysis of the former involves only one measurement of proper time whereas the latter requires two.

In other words, when the twins reunite what they're comparing is the amount of proper time that has elapsed for each twin. But in the muon example there is only one amount of elapsed proper time involved, and that is the amount of proper time elapsed for the muon.

Proper time is the time that elapses between two events that occur at the same place. It's a relativistic invariant, meaning all observers will agree on its value regardless of their motion relative to it.

 

[jbriggs444]

Assuming that acceleration was not needed for a clock to move around, we could pretend that it is the blue one that moves away and that comes back later, and we would simply get reversed results. We can only make predictions when we know for sure which clock has accelerated.

Again, "not accelerated" is not the same as "motionless".

 

[Raymond Potvin]

Again, "not accelerated" is not the same as "motionless".

Motion is relative, so we cannot tell for sure if a body is in motion or not because we don't have an absolute reference frame in hand, but acceleration is absolute, so if we know a clock has accelerated, why not use that information to eliminate all the other possibilities?

 

[jbriggs444]

Motion is relative, so we cannot tell for sure if a body is in motion or not because we don't have an absolute reference frame in hand, but acceleration is absolute, so if we know a clock has accelerated, why not use that information to eliminate all the other possibilities?

Because it is unnecessary. While you keep claiming that it is necessary.

 

[Raymond Potvin]

Do you have a reference for this claim?

Einstein didn't say it this way, but he used the light clock mind experiment to explain SR, and all his space-time concept is based on the way light moves between moving bodies.

The reason I ask is that I was under the impression that the light clock is a pedagogical tool, used to explain relativity. And by the way, it is not the only way to explain it. Look, for example, at Bondi's k-calculus approach. No light clocks there!

No light clock traveling sideways to their motion in my simulation either, just light exchanged between inline moving mirrors. No need to calculate the time it takes, just to reverse its direction when it hits the mirrors and stop the watch each time it makes a roundtrip. There are often many ways to do things, but in principle, the simpler way is often the better.

Have you considered the possibility that the muon example and the twin trip example are fundamentally different? Analysis of the former involves only one measurement of proper time whereas the latter requires two.

In other words, when the twins reunite what they're comparing is the amount of proper time that has elapsed for each twin. But in the muon example there is only one amount of elapsed proper time involved, and that is the amount of proper time elapsed for the muon.

Proper time is the time that elapses between two events that occur at the same place. It's a relativistic invariant, meaning all observers will agree on its value regardless of their motion relative to it.

It actually takes the proper time of our clocks to know that the lab Muon decays faster than the atmospheric one, but we also have to know the distance the Muon had to travel before hitting the Earth's surface, thus we have to know where it started accelerating towards us.

 

[Raymond Potvin]

Because it is unnecessary. While you keep claiming that it is necessary.

It is necessary if we want to make constant predictions, not to understand how light moves between moving bodies. I could have chosen not to consider acceleration in my simulation, and it would have given the same simulation, but it is the blue clock that would have suffered time dilation. From a relative viewpoint, the only thing that differentiates the clocks is acceleration.

 

[Ibix]

It actually takes the proper time of our clocks to know that the lab Muon decays faster than the atmospheric one, but we also have to know the distance the Muon had to travel before hitting the Earth's surface, thus we have to know where it started accelerating towards us.

But the muon isn't accelerating at any point, as has been pointed out before.

 

[Ibix]

It is necessary if we want to make constant predictions, not to understand how light moves between moving bodies. I could have chosen not to consider acceleration in my simulation, and it would have given the same simulation, but it is the blue clock that would have suffered time dilation. From a relative viewpoint, the only thing that differentiates the clocks is acceleration.

Time dilation is not the same as differential aging. No clock "suffers" time dilation ever.

 

[Raymond Potvin]

But the muon isn't accelerating at any point, as has been pointed out before.

A Muon is a massive particle that has to get its speed from acceleration, so it has to accelerate from the point where it is created. It may get that speed quite fast, but it cannot get it instantly because, being massive, it has to resist being accelerated.

 

[Ibix]

A Muon is a massive particle that has to get its speed from acceleration, so it has to accelerate from the point where it is created. It may get that speed quite fast, but it cannot get it instantly because, being massive, it has to resist being accelerated.

You are here assuming an absolute rest frame, in contradiction to relativity.

 

[PeterDonis]

The thread has gone off topic and the original qustion has been answered. Thread closed.

 

[PeterDonis]

To clear up a couple of misstatements:

That problem is solved using the Sagnac effect, not relativity.

The "Sagnac effect" is not something separate from "relativity". It's a prediction of relativity.

A Muon is a massive particle that has to get its speed from acceleration

Not if it's produced from something that already has that speed (relative to Earth, which is the "speed" you are implicitly assuming, though you have persistently refused to say so). Muons in the Earth's upper atmosphere are produced from the interaction of cosmic ray particles with air molecules. The speed the muons have relative to the Earth is the same as the center of mass speed of the system consisting of the incoming cosmic ray particles + the air molecules before the interaction. So the muons don't have to accelerate at all.

@Raymond Potvin feel free to PM me if you have questions about these responses; this thread will remain closed.