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Old 17th August 2020, 07:33 PM   #241
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Originally Posted by Robin View Post
That is where C is. Just do the calculations.
The event C cannot be there, it leads to t'=8s' and it does not exist.
The diagram is not good because the frames are not moving anymore after t'=2s'.
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Old 17th August 2020, 07:48 PM   #242
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This one is better:





Let see how the other frame view will turn out, I guess tomorrow.

Edit: I did it tonight.

The problem with the C event is still present.

Last edited by SDG; 17th August 2020 at 08:06 PM. Reason: 2nd diagram added
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Old 17th August 2020, 08:35 PM   #243
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Originally Posted by SDG View Post
This one is better:

https://i.imgur.com/6Xw9DFg.png



Let see how the other frame view will turn out, I guess tomorrow.

Edit: I did it tonight.

The problem with the C event is still present.
You didn't transform C correctly. That isn't where it is when you change frames.
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Old 17th August 2020, 09:02 PM   #244
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Originally Posted by SDG View Post
The platform and train frame before and after the acceleration.
And once again: You are not using the correct physics. Acceleration makes this a GR scenario. An instantaneous acceleration can be used in SR with different frames before and after the instantaneous acceleration. You need 3 frames say A (platform), B1 (train at the first speed) and B2 (train at the second speed). Any diagrams with 2 frames are immediately wrong.

Go back to the drawing board (literally) and state the scenario you want to look at in plain English.

Originally Posted by SDG View Post
The problem with the C event is still present.
You are still wrong, SDG. The problem remains that ignorance has lead to an incorrect analysis. Over a century of many experts and (millions?) students doing SR and GR calculations and matching the real world shows that they are correct.

Last edited by Reality Check; 17th August 2020 at 09:16 PM.
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Old 17th August 2020, 09:24 PM   #245
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Originally Posted by SDG View Post
The event C cannot be there, it leads to t'=8s' and it does not exist.
What do you mean, it doesn't exist? On what basis do you say it doesn't exist? Because the traveler didn't stay in that frame?

Sorry, that isn't how it works. The frame exists regardless.

Simultaneity is relative. You keep trying to make it absolute, and it isn't.

Quote:
The diagram is not good because the frames are not moving anymore after t'=2s'.
Only if you make one of the frames non-inertial. But that's a bad idea because your math skills aren't good enough to handle non-inertial frames. It's also completely unnecessary. The reference frame exists independent of the observer.
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Old 17th August 2020, 10:35 PM   #246
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Originally Posted by SDG View Post
Confused enough?
As always, the only person confused here is you. You will not succeed in infecting Ziggurat, Robin or Myriad with your confusion, no matter how much you unnecessarily complicate your examples, because they understand the textbook physics you don't.
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Old 17th August 2020, 11:07 PM   #247
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Originally Posted by SDG View Post
The platform and train frame before and after the acceleration.
It is a nonsense diagram - you have two origins. Of course you are going to confuse yourself if you create meaningless diagrams like this.

The situation is simple. The clock that has been accererating and decelerating with respect to a frame will measure a different time to the clocks that have remained stationary in that frame.
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Old 17th August 2020, 11:14 PM   #248
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Originally Posted by SDG View Post
The event C cannot be there, it leads to t'=8s' and it does not exist.
The diagram is not good because the frames are not moving anymore after t'=2s'.
I don't know what you mean when you say 8 seconds does not exist.

Let us just suppose we take the three events A, B and C just as events with no other significance than their coordinates, and we transform them between two inertial frames, the second moving at 0.866c with respect to the other:

A=(0,0,0,0) A'=(0,0,0,0)
B=(4,3.464,0,0) B'=(2,0,0,0)
C=(4,0,0,0) C'=(8,-6.928,0,0)

If my calculations there are wrong, then show me what is wrong with them.

On a diagram:

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Last edited by Robin; 17th August 2020 at 11:16 PM.
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Old 18th August 2020, 12:05 AM   #249
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SDG,

So what you are saying is that a traveller accelerates and then decelerates until he reaches v=0 at event B and remains stationary.



Yes?

However the second frame here is not really relevant as the traveller not in any inertial frame during his journey. Just to zoom in on A:



The traveller carries a clock and we would have to do some calculus to find out what the clock reads when he reaches B, but not too far off 2 seconds.

But he will step out and if he reads a clock that has been stationary in that platform he will read 4 seconds.

About a million kilometers away from him is C, and another clock that reads 4 seconds.

So where does this 8 seconds come in?

As I understand it, this is kind of reaching the limits of what it is sensible to try to do in SR.
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Old 18th August 2020, 12:06 AM   #250
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Originally Posted by SDG View Post
This one is better:

https://i.imgur.com/6Xw9DFg.png



Let see how the other frame view will turn out, I guess tomorrow.

Edit: I did it tonight.

The problem with the C event is still present.
When you are ready to get back to discussing relativity, just let us know.
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Last edited by Robin; 18th August 2020 at 12:26 AM.
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Old 18th August 2020, 06:34 AM   #251
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Originally Posted by Ziggurat View Post
You didn't transform C correctly. That isn't where it is when you change frames.
Where is the C event when the frames are changed?
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Old 18th August 2020, 06:37 AM   #252
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Originally Posted by Ziggurat View Post
What do you mean, it doesn't exist? On what basis do you say it doesn't exist? Because the traveler didn't stay in that frame?

Sorry, that isn't how it works. The frame exists regardless.

Simultaneity is relative. You keep trying to make it absolute, and it isn't.



Only if you make one of the frames non-inertial. But that's a bad idea because your math skills aren't good enough to handle non-inertial frames. It's also completely unnecessary. The reference frame exists independent of the observer.
After 2s' both frames have identical simultaneity, the horizontal lines, ...
Do you agree?
I did not say absolute.
The twins are in the same frame after 2s', aren't they?
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Old 18th August 2020, 06:39 AM   #253
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Originally Posted by Robin View Post
It is a nonsense diagram - you have two origins. Of course you are going to confuse yourself if you create meaningless diagrams like this.

The situation is simple. The clock that has been accererating and decelerating with respect to a frame will measure a different time to the clocks that have remained stationary in that frame.
Please, go ahead, fix the diagram.
Just remember that both twins are in the same frame before and after acceleration/deceleration.
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Old 18th August 2020, 06:40 AM   #254
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Originally Posted by Robin View Post
I don't know what you mean when you say 8 seconds does not exist.

Let us just suppose we take the three events A, B and C just as events with no other significance than their coordinates, and we transform them between two inertial frames, the second moving at 0.866c with respect to the other:

A=(0,0,0,0) A'=(0,0,0,0)
B=(4,3.464,0,0) B'=(2,0,0,0)
C=(4,0,0,0) C'=(8,-6.928,0,0)

If my calculations there are wrong, then show me what is wrong with them.

On a diagram:

https://robinsrevision.files.wordpre...-13.png?w=1024
You did not capture that both twins are in the same frame before and after acceleration/deceleration.
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Old 18th August 2020, 06:44 AM   #255
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Originally Posted by SDG View Post
This one is better:

https://i.imgur.com/6Xw9DFg.png
The more I think about this, the more baffled I am. Not by the relativity problem, but by you, and how you can not only still fail to understand fundamental aspects of relativity, but not even notice that there's an issue with your understanding.

You've posted two images:



First, you're trying to make a non-inertial reference frame look like an inertial reference frame. It won't work. Non-inertial frames are weird. I keep telling you this, but you keep ignoring it and trying to pretend that a non-inertial frame is inertial.

But here's the kicker, which even you should have noticed. In your bottom image, you've got distinct ct and ct' axes in both images. But you marked your x and x' axes as being the same. So this isn't even an issue of you forgetting about x'. You remembered. You remembered, and decided to make x and x' the same.

THEY ARE NOT THE SAME.

Look at your top image. See that x axis and that x' axis? See how they are tilted with respect to each other? You cannot ignore that and expect to get anything even remotely sensible out of relativity. You can't ignore a key component of ANY theory and expect the theory to make sense.
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Old 18th August 2020, 06:48 AM   #256
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Originally Posted by Robin View Post
SDG,
...
So where does this 8 seconds come in?

As I understand it, this is kind of reaching the limits of what it is sensible to try to do in SR.
Robin,
good honest statement.








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Old 18th August 2020, 06:52 AM   #257
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Robin,
The previous post math looks scary, right.
... but this is still true.





We can do average.
You have a good idea.
The only thing what I am trying to say that at the mid point P the twins are in the same frame.
They are.
So what does it mean?
The trouble with the simplified traveling twin point of view diagram.
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Old 18th August 2020, 06:59 AM   #258
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Originally Posted by Ziggurat View Post
...
First, you're trying to make a non-inertial reference frame look like an inertial reference frame. It won't work. Non-inertial frames are weird. I keep telling you this, but you keep ignoring it and trying to pretend that a non-inertial frame is inertial.
...

I do completely understand that.
Who came with the X/R idea to make them look inertial?
I am trying to point out that this is not so simple as yours and all relativity community X/R approach.
This is some nice double standard.
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Old 18th August 2020, 07:03 AM   #259
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Originally Posted by Ziggurat View Post
...
But here's the kicker, which even you should have noticed. In your bottom image, you've got distinct ct and ct' axes in both images. But you marked your x and x' axes as being the same. So this isn't even an issue of you forgetting about x'. You remembered. You remembered, and decided to make x and x' the same.

THEY ARE NOT THE SAME.
...


The x, x' is not important during the acceleration/deceleration in this diagram as well.
What is important is that before and after a/d they have the same size ruler.
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Old 18th August 2020, 07:08 AM   #260
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Originally Posted by SDG View Post
You did not capture that both twins are in the same frame before and after acceleration/deceleration.
On the contrary I have illustrated the situation where they have the same velocity after the acceleration and deceleration in the very next post.
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Old 18th August 2020, 07:10 AM   #261
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This is the 'weirdness' of the relativity.
The traveling twin goes 1010 light years away.
Then he stops and the stayed home frame origin traveled 1010 light years in 90 years from travelers point of view.
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Old 18th August 2020, 07:12 AM   #262
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Originally Posted by Robin View Post
On the contrary I have illustrated the situation where they have the same velocity after the acceleration and deceleration in the very next post.
Please, try to do it with the traveling twin point of view diagram.
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Old 18th August 2020, 07:29 AM   #263
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Originally Posted by SDG View Post
I do completely understand that.
Who came with the X/R idea to make them look inertial?
That wasn't to make the traveler look inertial. The traveler is not inertial, and cannot be inertial.

That was to simplify the math. The section you copied from a book? All those calculations were done from an inertial reference frame. I told you a long time ago that there's a difference between using an accelerating reference frame and using an inertial reference frame to look at an accelerating object, but you didn't pay attention.

Everything about this problem can be done from an inertial reference frame, including calculating trajectories with finite acceleration. There is never a need to go to a non-inertial frame. That's not unique to special relativity either: Newtonian mechanics is easier in an inertial frame as well.

Quote:
I am trying to point out that this is not so simple as yours and all relativity community X/R approach.
This is some nice double standard.
There is no double standard, only your lack of understanding of the distinction between an accelerating object and an accelerating reference frame.

You are growing tiresome with your refusal to learn anything, and your repetition of mistakes you made pages and pages ago.
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Old 18th August 2020, 07:33 AM   #264
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Originally Posted by Ziggurat View Post
That wasn't to make the traveler look inertial. The traveler is not inertial, and cannot be inertial.

That was to simplify the math. The section you copied from a book? All those calculations were done from an inertial reference frame. I told you a long time ago that there's a difference between using an accelerating reference frame and using an inertial reference frame to look at an accelerating object, but you didn't pay attention.

Everything about this problem can be done from an inertial reference frame, including calculating trajectories with finite acceleration. There is never a need to go to a non-inertial frame. That's not unique to special relativity either: Newtonian mechanics is easier in an inertial frame as well.



There is no double standard, only your lack of understanding of the distinction between an accelerating object and an accelerating reference frame.

You are growing tiresome with your refusal to learn anything, and your repetition of mistakes you made pages and pages ago.
You treated the accelerated frames as inertial, right?
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Old 18th August 2020, 07:33 AM   #265
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Originally Posted by SDG View Post
Please, try to do it with the traveling twin point of view diagram.
You can't do that in SR and there is no point in trying.

To treat an accelerated observer as stationary you have to have him.coming under the influence of gravitational fields. You need GR for that.
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Old 18th August 2020, 07:37 AM   #266
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Originally Posted by SDG View Post
Robin,

The previous post math looks scary, right. .
Not really, maths is usually a matter of patience and time. But the detail is not really relevant here.
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Old 18th August 2020, 07:41 AM   #267
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Originally Posted by Robin View Post
You can't do that in SR and there is no point in trying.

To treat an accelerated observer as stationary you have to have him.coming under the influence of gravitational fields. You need GR for that.
Maybe my post #79 could more understandable now.
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Old 18th August 2020, 07:41 AM   #268
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Originally Posted by SDG View Post
You treated the accelerated frames as inertial, right?
Do you even know what a reference frame is? Do you even know what inertial is?

The entire god damn point of an inertial reference frame is that it's not accelerating. That doesn't mean that things WITHIN the frame don't accelerate, but if you accelerate the reference frame itself, it is BY DEFINITION not inertial.

The fact that you're even asking this question shows a deep, profound confusion about even the most basic terms we're discussing. And this isn't unique to special relativity. Go back to Newtonian mechanics, and your question is still absolute nonsense. This error is fatal in any kind of mechanics.
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Old 18th August 2020, 07:49 AM   #269
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Originally Posted by SDG View Post
https://i.imgur.com/Ec2Ot1k.png

The x, x' is not important during the acceleration/deceleration in this diagram as well.
You are wrong. The fact that they tilt is critical, even if they tilt back. The movement of the lines of simultaneity accounts for exactly what you think is missing.

You keep trying to treat non-inertial frames as if they were inertial. Possibly because you don't understand what inertial means, or even what reference frames are, as your last post demonstrates.
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Old 18th August 2020, 07:58 AM   #270
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Originally Posted by Ziggurat View Post
Do you even know what a reference frame is? Do you even know what inertial is?

The entire god damn point of an inertial reference frame is that it's not accelerating. That doesn't mean that things WITHIN the frame don't accelerate, but if you accelerate the reference frame itself, it is BY DEFINITION not inertial.

The fact that you're even asking this question shows a deep, profound confusion about even the most basic terms we're discussing. And this isn't unique to special relativity. Go back to Newtonian mechanics, and your question is still absolute nonsense. This error is fatal in any kind of mechanics.
What was this discussion about?
You treated the accelerated frames as inertial.
Can you be reasonable?

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Old 18th August 2020, 08:06 AM   #271
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Originally Posted by Ziggurat View Post
You are wrong. The fact that they tilt is critical, even if they tilt back. The movement of the lines of simultaneity accounts for exactly what you think is missing.

You keep trying to treat non-inertial frames as if they were inertial. Possibly because you don't understand what inertial means, or even what reference frames are, as your last post demonstrates.
Yes, tilt is critical because it shows how much the traveling twin gets to be like a photon on average.
Still, this does not change the fact that before and after the acceleration/deceleration the x, x' have the same size ruler.
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Old 18th August 2020, 08:07 AM   #272
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Originally Posted by SDG View Post
What was this discussion about?
You treated the accelerated frames as inertial.
What are you on about? I didn't treat accelerated FRAMES as inertial. I looked at the problem from three NON-accelerating inertial frames. The frames don't accelerate. Travelers within the frames accelerate, not the frames. All frames in that diagram are inertial, and do not accelerate.

Quote:
Can you be reasonable?
Can you actually try to understand what we're saying?
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Old 18th August 2020, 08:09 AM   #273
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Originally Posted by SDG View Post
Yes, tilt is critical because it shows how much the traveling twin gets to be like a photon on average.
Still, this does not change the fact that before and after the acceleration/deceleration the x, x' have the same size ruler.
But not during, and that's critical. It doesn't just affect distance, it affects time as well.
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Old 18th August 2020, 08:22 AM   #274
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OK, SDG, here's a possible source of some of your confusion.

Do you remember when I talked about why it was OK to simplify the problem by ignoring the acceleration? That if we lengthen the non-accelerated portion of the journey, then it becomes an irrelevant perturbation?

Well, that's true. But I think you missed part of it. That's true IF AND ONLY IF you work in an inertial reference frame, which I was assuming because that's the only sensible thing to ever do in special relativity.

If you try to work in an accelerated frame, that is no longer true. No matter how much you extend the non-accelerated portion of the journey, it will never cancel out the effects of acceleration. Why? Because the longer you make that un-accelerated portion of the journey, the farther away the stationary twin is when the the traveling twin undergoes acceleration. Do you remember what I said about fictitious forces in Newtonian mechanics? About how they're position dependent? Same applies here: the farther away something is, the larger the effects of acceleration are in the accelerating reference frame. They scale with each other. Make X bigger, and the effect gets bigger. Which means that the effect NEVER cancels, no matter how long you make the non-accelerating portion of the journey, if you try to work in an accelerating reference frame.

But again, there is simply no need to ever do any special relativity problem in an accelerating reference frame. It just makes problems harder, with no benefit.
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Old 18th August 2020, 08:26 AM   #275
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Originally Posted by Ziggurat View Post
What are you on about? I didn't treat accelerated FRAMES as inertial. I looked at the problem from three NON-accelerating inertial frames. The frames don't accelerate. Travelers within the frames accelerate, not the frames. All frames in that diagram are inertial, and do not accelerate.



Can you actually try to understand what we're saying?
This leads to X/R solution where R has to take care of the unrealistic 'jump'.
Do you know that time elapsed in R is a function of distance from the stay home point of view frame?
It means that two inertial observers do not agree on how much time elapsed inside the R period for the traveling twin.
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Old 18th August 2020, 08:48 AM   #276
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Originally Posted by SDG View Post
This leads to X/R solution where R has to take care of the unrealistic 'jump'.
Yes, if you want to work with an accelerating reference frame.

But there is no reason to ever do that.

Quote:
Do you know that time elapsed in R is a function of distance from the stay home point of view frame?
You have that backwards. The time that the accelerating observer will observe (not see) passing is dependent on distance, but that's what I just told you in my previous post. There is no distance dependence for what an inertial observer observes (not sees).

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It means that two inertial observers do not agree on how much time elapsed inside the R period for the traveling twin.
No, it doesn't mean anything of the sort. That distance dependence applies to NON-inertial observers. It doesn't apply inertial observers.
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Old 18th August 2020, 08:50 AM   #277
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Originally Posted by SDG View Post
After 2s' both frames have identical simultaneity, the horizontal lines, ...
Do you agree?
I did not say absolute.
The twins are in the same frame after 2s', aren't they?
This is the most common mistake from beginners trying to understand relativity.

No, the frames moving relative to each other do not share simultaneity. Two observers, looking at the same third event (separated from both observers), will disagree on what time that event is currently experiencing. They will disagree on how the time-axis is aligned for the other observer.

For two observers, U and U', U will see:


The markings on the space axies x and x' are the same distance apart, from the views of U and U', respectively. The same applies for the time markings on the time axies ct and ct'.

The "T=" lines are drawn parallel to each respective space axis: x or x'. The observers U and U' fundamentally do not agree on what "T=" is for nearly every possible event (x,ct). And when they do, they disagree on what "x=". Only when they are together can they agree, and then only on the fact that they are together. Everything else is seen differently for each moving observer.

The math is quite hard to imagine, as there are no simple processes in nature that act similarly, so our brains never really needed to learn how to visualize or intuit such transformations. Fortunately, Henry Reich from Minute Physics made a physical "Spacetime globe" that allows you to rotate between the different frames of reference, much like a globe of the earth allows you to rotate the earth between different times of day and/or different values of "up". Seeing the actual 'squash-stretch' of the Lorentz transforms makes it much easier to have a proper intuition about relativity. I highly recommend this series to anyone starting down the path to understanding physics.
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Old 18th August 2020, 08:52 AM   #278
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Originally Posted by Ziggurat View Post
OK, SDG, here's a possible source of some of your confusion.

Do you remember when I talked about why it was OK to simplify the problem by ignoring the acceleration? That if we lengthen the non-accelerated portion of the journey, then it becomes an irrelevant perturbation?

Well, that's true. But I think you missed part of it. That's true IF AND ONLY IF you work in an inertial reference frame, which I was assuming because that's the only sensible thing to ever do in special relativity.

If you try to work in an accelerated frame, that is no longer true. No matter how much you extend the non-accelerated portion of the journey, it will never cancel out the effects of acceleration. Why? Because the longer you make that un-accelerated portion of the journey, the farther away the stationary twin is when the the traveling twin undergoes acceleration. Do you remember what I said about fictitious forces in Newtonian mechanics? About how they're position dependent? Same applies here: the farther away something is, the larger the effects of acceleration are in the accelerating reference frame. They scale with each other. Make X bigger, and the effect gets bigger. Which means that the effect NEVER cancels, no matter how long you make the non-accelerating portion of the journey, if you try to work in an accelerating reference frame.

But again, there is simply no need to ever do any special relativity problem in an accelerating reference frame. It just makes problems harder, with no benefit.
Here is the inertial frame, the red line.
How do we do the diagram from the red line point of view between A and P.
There is a stop at P, no more motion.
How do we do that?

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Old 18th August 2020, 09:13 AM   #279
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Originally Posted by SDG View Post
Here is the inertial frame, the red line.
THE inertial frame?

No. The red line covers two DIFFERENT inertial reference frames.

Quote:
How do we do the diagram from the red line point of view between A and P.
There is a stop at P, no more motion.
How do we do that?
It would look something like this:



The black are the axes for the stay at home twin. The red is for the traveling twin while he's traveling. The blue is for the traveling twin after he stops at point P. Note that the x axis has to shift.

This drawing is not to scale, I eyeballed it, but you can do the same thing by calculating specific numbers easily enough.
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Old 18th August 2020, 09:30 AM   #280
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Originally Posted by Ziggurat View Post
THE inertial frame?

No. The red line covers two DIFFERENT inertial reference frames.



It would look something like this:


The black are the axes for the stay at home twin. The red is for the traveling twin while he's traveling. The blue is for the traveling twin after he stops at point P. Note that the x axis has to shift.

This drawing is not to scale, I eyeballed it, but you can do the same thing by calculating specific numbers easily enough.
This is very hard to understand.
I consider this as the stay home frame view but it does not make sense to me, what are the blue lines?
How about to have the red timeline vertical, not under the angle.
I am interested where the C event is going to be.
If we go but the same numbers as I used, C event is 4s of the stay home twin on his timeline.

Isn't it just one frame between A and P?

Last edited by SDG; 18th August 2020 at 09:34 AM.
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