Acceleration is not important in the twin paradox

[Delta1212]

You have the math to work with, the language of physics is math, "literary composition" doesn't cut it.

This problem is judged from one frame only , so it has nothing to do with RoS. Perhaps if you stopped making sweeping statements and you started writing math, you could be more believable. For the time being, not.

If B anC have the same speed, B is irrelevant to the problem, the paradox reduces to the form where B turns around instantaneously, with infinite acceleration. This is the fourth time when I point this out. No matter how you three guys twist and turn, the paradox is explained only in the presence of acceleration.

Yes, it reduces to the form that B turns around with infinite acceleration, but B doesn't actually turn around. It is the equivalent of an accelerated frame of reference, but were this experiment conducted in the real world, there is no object that would actually accelerate to achieve this.

[xyzt]

Yes, it reduces to the form that B turns around with infinite acceleration, but B doesn't actually turn around. It is the equivalent of an accelerated frame of reference, but were this experiment conducted in the real world, there is no object that would actually accelerate to achieve this.

Yes, the infinite acceleration is replaced with a frame swap at the midpoint where B and C meet. I pointed out the frame-jumping at the very beginning of the thread.

 

 

Am I to understand that you think this refers to one frame?...

 

 

You do understand that "according to A" is a different frame from "according to C", and that their simultaneity is relative?

 

I think this may be the source of the problem.

 

 

The whole explanation is "according to A" in calculating the elapsed proper time for B and C.

The only exception is the calculation of total elapsed proper time for A. RoS never enters into the picture, especially when calculating elapsed proper time.

So, please stop making up strawmen. I am used to arguing with people like you, you will never admit to error, this doesn't mean that you are correct.

Edited May 6, 2013 by xyzt

[Delta1212]

Yes, the infinite acceleration is replaced with a frame swap at the midpoint where B and C meet. I pointed out the frame-jumping at the very beginning of the thread.

Yes, the measurement swaps frames. But nothing accelerates in the physical world.

[xyzt]

Yes, the measurement swaps frames. But nothing accelerates in the physical world.

Frame swapping (jumping) is the same thing as infinite acceleration.

The situation is pretty bad when u=v (v_B=v_C). It only gets much worse (see writeup) when the speeds are different.

Edited May 6, 2013 by xyzt

[Delta1212]

Frame swapping (jumping) is the same thing as infinite acceleration.

In terms of the math, yes. md isn't arguing that changing frames isn't the cause of the twin paradox. He's trying to illustrate that the physical act of acceleration by an observer doesn't create the time discrepancy, but rather the fact that acceleration causes the observer to change frames, which is responsible for the difference because the change in frames results in that discrepancy regardless of whether a physical thing underwent any acceleration.

Edited May 6, 2013 by Delta1212

[Iggy]

The whole explanation is "according to A" in calculating the elapsed proper time for B and C...

 

No, the expression is as follows:

According to A, A ages 4 years, while C ages 2 years.

According to C, A ages 4 years, while C ages 8 years..

The only reference to proper time here is the age of A according to A and the age of C according to C. A is not talking about the proper time of C and C is not talking abut the proper time of A.

 

I'm sorry you misunderstood that, but Md did clarify and the language used in the indented section above is typical when discussing relativity problems.

Edited May 6, 2013 by Iggy

[xyzt]

 

No, the expression is as follows:

According to A, A ages 4 years, while C ages 2 years.

According to C, A ages 4 years, while C ages 8 years..

The only reference to proper time here is the age of A according to A and the age of C according to C. A is not talking about the proper time of C and C is not talking abut the proper time of A.

 

I'm sorry you misunderstood that, but Md did clarify and the language used in the indented section above is typical when discussing relativity problems.

The twin paradox is judged from a single, unique frame perspective (A , in the case above). I am sorry that you don't know this elementary fact. If you compare apples and oranges, don't be surprised that you get ....bananas.

In terms of the math, yes. md isn't arguing that changing frames isn't the cause of the twin paradox. He's trying to illustrate that the physical act of acceleration by an observer doesn't create the time discrepancy, but rather the fact that acceleration causes the observer to change frames, which is responsible for the difference because the change in frames results in that discrepancy regardless of whether a physical thing underwent any acceleration.

I know he's trying to do that. The counter-argument is that the acceleration is there, it is hidden (or he doesn't see it).

Edited May 6, 2013 by xyzt

[Iggy]

The twin paradox is judged from a single perspective (A , in the case above).

 

Md never mixed frames in the post referenced. He discussed the perspective of A and the perspective of C and got the correct answer for both.

 

You didn't understand him. That is no reason to be belligerent.

[xyzt]

Md never mixed frames in the post referenced.

Neither have I. I was talking about my calculations, not his. You need to pay attention.

On the other hand, it doesn't matter if md's calculations are right, the point is that they hide the presence of acceleration, this is what the debate is all about. You need to pay attention.

Edited May 6, 2013 by xyzt

[Delta1212]

The twin paradox is judged from a single, unique frame perspective (A , in the case above). I am sorry that you don't know this elementary fact. If you compare apples and oranges, don't be surprised that you get ....bananas.

I know he's trying to do that. The counter-argument is that the acceleration is there, it is hidden (or he doesn't see it).

What object physically undergoes acceleration? Not "it's equivalent to x object undergoing acceleration" but which object actually accelerates?

[xyzt]

What object physically undergoes acceleration? Not "it's equivalent to x object undergoing acceleration" but which object actually accelerates?

Arbitrarily advancing/regressing C's clock is , in terms of calculating elapsed time, nothing but a jump in speed, i.e......acceleration. This is precisely what happens at the meeting point, where C resets his clock to the value of B. I thought that was very clearly explained in my writeup.

[Iggy]

Neither have I. I was talking about my calculations, not his. You need to pay attention.

 

I'm terribly sorry, but your post:

 

You are still wrong, proper time does not depend on the observer, it is frame invariant. So you cannot have:

 

"According to A, A ages 4 years, while C ages 2 years.

According to C, A ages 4 years, while C ages 8 years.."

 

I cannot ever agree with the stuff you just wrote, basic SR says you are wrong and you continue along the path of being wrong.

 

belligerently addresses Md's calculation, and calls it wrong when it is plainly correct. If you solved an unrelated problem and got a different answer then that's fine, but that isn't what you're talking about above.

 

On the other hand, it doesn't matter if md's calculations are right...

 

If it doesn't matter then I suggest you go back and edit your post.

Edited May 6, 2013 by Iggy

[xyzt]

belligerently addresses Md's calculation, and calls it wrong when it is plainly correct. If you solved an unrelated problem and got a different answer then that's fine, but that isn't what you're talking about above.

Elapsed proper time is frame invariant, so it doesn't depend on the frame of reference . To make things simple, you can choose a single frame , in this case the frame chosen was A. If, on the other hand, you get different results when calculating from different frames of reference, it means that you have the wrong result. So, you can stop defending a wrong position for the time being.

Edited May 6, 2013 by xyzt

[md65536]

Arbitrarily advancing/regressing C's clock is , in terms of calculating elapsed time, nothing but a jump in speed, i.e......acceleration.

Acceleration does not cause a jump in proper time of the accelerating object (this is the clock postulate).

 

You're misunderstanding the most basic version of the twin paradox. You're lending weight to the point I tried to make in the first post.

[xyzt]

Acceleration does not cause a jump in proper time of the accelerating object (this is the clock postulate).

 

 

True, it is the sleigh of hand in resetting the C clock to the B value that does the trick. The point is that you created a BOGUS scenario to give creedence to your claim that you can generate a "twin paradox without acceleration".

All you have done is to create a BOGUS scenario where you fiddle with C clock midway and you hope to hide the sleigh of hand. In the beginning, I thought that you honestly did not realize what you have done but, after all these exchanges, I am beginning to doubt that. I think you fully know the extent of your sleigh of hand but you think that denying it will make it go away.

Edited May 6, 2013 by xyzt

[Iggy]

Elapsed proper time is frame invariant, so it doesn't depend on the frame of reference . To make things simple, you can choose a single frame , in this case the frame chosen was A. If, on the other hand, you get different results when calculating from different frames of reference, it means that you have the wrong result. So, you can stop defending a wrong position for the time being.

 

Ok, X.

 

If anyone discusses a frame of reference, or anything else, that you aren't talking about then they are wrong. Even if they are correct, they are wrong.

 

Ok.

[xyzt]

Ok, X.

 

If anyone discusses a frame of reference, or anything else, that you aren't talking about then they are wrong. Even if they are correct, they are wrong.

 

Ok.

It is really simple: elapsed proper time is frame invariant, if you get different results depending on the frame of reference, you have done something wrong. Like you defending an indefensible calculation.

[Iggy]

It is really simple: elapsed proper time is frame invariant, if you get different results depending on the frame of reference, you have done something wrong. Like you defending an indefensible calculation.

 

We've been over that. Everyone knows that proper time is invariant. They aren't proper times. The things in bold are *not* proper times:

 

According to A, A ages 4 years, while C ages 2 years.

According to C, A ages 4 years, while C ages 8 years..

It is worded as clearly as could be, and is the most common of language when discussing relativity.

 

According to C, A ages 4 years while C ages 8 years, obviously. You disagree? You think A ages some different amount while C ages 8 years according to C? In C's frame of reference, how long exactly do you think A ages while *in C's frame of reference* C ages 8 years?

 

Give me a number. Everything is in C's frame of reference. That's what "according to C" means. In that frame: A approaches C. A meets up with C. How much younger would he calculate A to be when he was 8 years younger.

 

Give me a number. Don't change the problem. Don't answer a different question.

 

Give me a number.

[xyzt]

We've been over that. Everyone knows that proper time is invariant. They aren't proper times.

Apparently, you don't know. The twins paradox is all about comparing proper times.

Oh, one last thing, you should learn how to express physics in symbolic math. All this stuff about numbers reeks of not knowing how to express yourself.

Edited May 6, 2013 by xyzt

[Iggy]

Apparently, you don't know. The twins paradox is all about comparing proper times.

Oh, one last thing, you should learn how to express physics in symbolic math. All this stuff about numbers reeks of not knowing how to express yourself.

 

I understand that you only want to discuss proper times.

 

I also understand that Md mentioned something that wasn't a proper time, but that was nevertheless 100% correct.

 

I also understand that you misunderstood him, and thought that he was giving a proper time, so you took the occasion to belligerently insult his knowledge of relativity telling him how wrong he was. It was the second time he said something perfectly reasonable and true only for you to dismissively insult the claim as wrong, because it wasn't something that you were considering.

 

See, Xyzt, Everyone here understands what you are perfectly.

[xyzt]

I understand that you only want to discuss proper times.

Good, because elapsed proper time is what the twins "paradox" is all about. Anything else, you can open a different thread and discuss it to your heart content, please stop trying to hijack this thread.

Edited May 6, 2013 by xyzt

[Iggy]

please stop trying to hijack this thread.

 

Please retract this claim:

 

You are still wrong, proper time does not depend on the observer, it is frame invariant. So you cannot have:

 

"According to A, A ages 4 years, while C ages 2 years.

According to C, A ages 4 years, while C ages 8 years.."

 

I cannot ever agree with the stuff you just wrote, basic SR says you are wrong and you continue along the path of being wrong.

 

while you're at it, retract this one:

 

...you claimed that "Everyone will agree on what time the two passing clocks read at the moment they pass each other." When I showed you that the claim is false... I cannot teach you, I am sorry.

 

Md clearly has a good understanding of relativity, and you keep insulting him for saying things that are perfectly true and consistent with SR. Stop hijacking this thread, indeed.

Edited May 6, 2013 by Iggy

[Delta1212]

xyzt, would you say this statement is accurate:

 

Adding the proper time measured by Clock B between events AB and BC to the proper time measured by Clock C between events BC and AC will yield a number that is equivalent to the proper time experienced by an observer that travels from event AB to event BC and then instantly accelerates to travel back to event AC?

[xyzt]

xyzt, would you say this statement is accurate:

 

Adding the proper time measured by Clock B between events AB and BC to the proper time measured by Clock C between events BC and AC will yield a number that is equivalent to the proper time experienced by an observer that travels from event AB to event BC and then instantly accelerates to travel back to event AC?

 

 

What are events AB, BC, AC?

[Delta1212]

AB is Clock B passing Clock A (or the observer leaving A), BC is Clock B passing Clock C (or the observer reaching the equivalent point in space and turning around), AC is Clock C passing Clock A (or the observer returning to A).