Twin paradox (Pete and MacM)

[MacM]

So it's not a problem for you that in B's reference frame, clock A keeps ticking after clock B stops?

I see simultaneity as information delay, so in that regard, no I have no problem with it but I did and do have a problem when physical clocks are stopped and simultaneity is then used to claim that the clock continues to accumulate time. That is what was being claimed in that thread.

My point was that because of simultaneity the clocks were ACTUALLY stopped and the recorded times caused the observer to believe they were stopped prematurely.

That is the actual consequence of stopping all clocks in a given frame. The clocks do not continue to run and alter the recorded time. So my rejection was not based on a rejection of simultaneity but the erroneous application of simultaneity as a counter arguement against the clock readings I was preducing.

Hope that clairifies.

 

[MacM]

It is not that the other frames do not see it as being simultaneous, it is that it is not simultaneous in their frames.


What "anticipated beliefs" would those be. All the clocks were pre-programed to stop at pre-determined readings. Thus if clock A were pre-programed to stop when it read 10 hrs, the only "anticipated belief' that clock observers B & C could have is that clock A stopped when it read 10 hrs, regardless of what time clock A read according to B or C when B or C themselves stopped.

(And when I say the time clock A reads according to B or C, I do not mean what they see clock A reading, but the actual time on clock A at that instant according to A or B.)

I certainly will agree that knowing there was a timer preset to stop the clocks should not cause one to be surprised they stopped when they did. But you have to recall the circumstances whereby I used that tactic. Members here would not allow me to claim a variety of methods of stopping clocks simultaneously.

Indeed chroot made a big challenge that it couldn't be done. Since you seem to recall that thread you should also recall that I egged him on a bit for 2 - 3 days and wouldn't tell him how I was going to do it and he became rather abusive.

But as simple as the technique appears on the surface it was based entirely on Relativity. By assuming relativity is valid, the system used precalculated timers to actually stop the clocks simultaneoulsy.

While chroot objected to the procedure as showing nothing about time dilation only that the "THE FUC_ING CLOCKS AREN'T BROKEN" HeHeHe, it in reality was a very appropriate solution since the objective was to look at the recorded times per relativity of the clocks if they are stopped simultaneoulsy and was not an exercise in how to synchronize clocks.

But the most important aspect of that little exercise should not be forgotten. The clock readings do not match observer expectations upon comparision.

i.e. At 0.9c when "A" simultaneously shuts down all clocks after 10 hours, "B" reads 4.359 hours. Which is expected and which was built into the timer control system. However "B's" relavistic view that "A" should have read 1.9 hours is not upheld. It physically reads 10 hours.

Therein lies the issue.

 

[Pete]

Mac, I think you need to carefully examine the concepts involved here.

You stated that you accept that simultaneity alter due to perspective. It's time to clearly state exactly what you mean.

Think about the scenario of two objects (A and B) firing signals toward each other.
It is clear that when A and B have equal and opposite velocities (our mean velocity frame), that if the signals are emitted simultaneously they are received simultaneously.

However, in this diagram:
<img src="/attachment.php?attachmentid=3349&stc=1">

It is clear that in A's frame, when the signals are emitted simultaneously, they are not received simultaneously. Similarly, if the signals are received simultaneously, they are not emitted simultaneously.

Now... think carefully about what that means...

It might help if you think of the signals as powerful lasers that will destroy their targets.

In one frame, A and B are destroyed simultaneously - these are real events!
In other frames, one is destroyed before the other...

So which one is really destroyed first? Does this question have an absolute answer? Or does the question lack information - is a reference frame needed to provide a meaningful answer?

 

[Pete]

I did and do have a problem when physical clocks are stopped and simultaneity is then used to claim...

But the whole question is whether the clocks were stopped simultaneously or not.

It is certain that the clocks were stopped simultaneously from A's perspective...

But what about from B's perspective?

When clock B stops at 35820 seconds, does clock A stop at the same time from B's perspective?

Or (since perspective alters the conclusion of what is simultaneous), could B conclude that clock A stops at some other time?

 

[Pete]

Here's an interesting question related to the basic concept of relativty:

How far am I?


Does that question have an absolute answer?
Does it require some frame of reference before a meaningful answer can be provided?

 

[MacM]

Mac, I think you need to carefully examine the concepts involved here.

You stated that you accept that simultaneity alter due to perspective. It's time to clearly state exactly what you mean.

Think about the scenario of two objects (A and B) firing signals toward each other.
It is clear that when A and B have equal and opposite velocities (our mean velocity frame), that if the signals are emitted simultaneously they are received simultaneously.

However, in this diagram:
<img src="/attachment.php?attachmentid=3349&stc=1">

It is clear that in A's frame, when the signals are emitted simultaneously, they are not received simultaneously. Similarly, if the signals are received simultaneously, they are not emitted simultaneously.

Now... think carefully about what that means...

It might help if you think of the signals as powerful lasers that will destroy their targets.

In one frame, A and B are destroyed simultaneously - these are real events!
In other frames, one is destroyed before the other...

So which one is really destroyed first? Does this question have an absolute answer? Or does the question lack information - is a reference frame needed to provide a meaningful answer?

I have been looking at your diagrams and frankly I have not yet been able to put my finger on what you are doing that isn't just quite right. But nor have I had that much time doing it.

My point is that done properly switching frames from A to B must produce equal but opposite results. Some of your diagrams don't seem to do that.

Have you seen my sketch explaining the differance between "Symmetry" and "Reciprocity"?

http://www.sciforums.com/attachment.php?attachmentid=3364&stc=1

Where a function may include acceleration, constant relative velocity and deceleration, the graph would not likely be symmetrical but reciprocity cancels even if it is not symmetrical. Gamma is not symmetrical.

Reciprocity is the result of switching frames from A to B.

 

[MacM]

But the whole question is whether the clocks were stopped simultaneously or not.

It is certain that the clocks were stopped simultaneously from A's perspective...

But what about from B's perspective?

When clock B stops at 35820 seconds, does clock A stop at the same time from B's perspective?

Or (since perspective alters the conclusion of what is simultaneous), could B conclude that clock A stops at some other time?

Here is I believe the root arguement. I claim, and I believe without any uncertainity, that by using the precalculated relavistically expected times on the clocks, to stop the clocks at times predicted by Relativity, that the clocks are IN FACT stopped simultaneously PERIOD.

The results of doing that causes the respective observers (assuming they are not aware of the timers shutting down the clocks) would believe that "A" stopped the test prematurely, not that the clocks didn't stop when they were supposed to and to be stopped simultaneously.

Doing so shows the affect I have been harping about all this time. At 0.9c "A" certainly reads 10 hours since that was the agreed test period. "B" reads just over 4 hours which is consistant with what "A's" frame would expect according to Relativity.

But clock "B" thinks because of simultaneity (information delay) that "A" stopped his clock prematurely. B also sees "A" as running slower than his clock and expects "A" to read 1.9 hours when his clock stopped at 4.359 hours, well before the 10 hours had elapsed.

But upon comparison of the physical clocks "B's" view of "A" is not up held instead of the relavistic view of "B" that it should read 1.9 hours it actually reads 10 hours.

Therein lies the issue.

I would be interested in seeing any rational arguement that that is not so.

 

[MacM]

Here's an interesting question related to the basic concept of relativty:

How far am I?


Does that question have an absolute answer?
Does it require some frame of reference before a meaningful answer can be provided?

I would say without hesitation you would certainly need to choose a referance point but I fail to see how this relates to the issue here.

 

[Pete]

My point is that done properly switching frames from A to B must produce equal but opposite results.

Only for symmetrical situations. This situation is not symmetrical.
Perhaps your notion of reciprocity is misguided?

the clocks are IN FACT stopped simultaneously PERIOD.

But you said before that perspective alters the conclusion of what is simultaneous.
Are you retracting that statement?
Or do you think that Clock B does not have an altered perspective to Clock A?

 

[Pete]

I have never denied simultaneity due to motion.

What exactly do you mean by the above sentence? Sometime you use the word "simultaneity" in strange ways.
In the context, you appear to mean that you have never denied that events which are simultaneous in one frame are not necessarily simultaneous in all frames... but you are clearly denying that when you maintain that "the clocks are IN FACT stopped simultaneously PERIOD."

 

[Pete]

I have been looking at your diagrams and frankly I have not yet been able to put my finger on what you are doing that isn't just quite right.

Keep looking.
One is tempted to conclude that your feeling of something not being right is due to your bias against the SR model - and nothing more.

 

[MacM]

Only for symmetrical situations. This situation is not symmetrical.

See my sketch on Reciprocity.

But you said before that perspective alters the conclusion of what is simultaneous.

Are you retracting that statement?

No. I am saying that the idea of simultaneity means he thinks his clock should not have stopped - but infact it does. Not that the clock stopped in "A's" frame actually continues to run because B sees a different simultaneity. Simultaneity only suggests to B as to when his clock should stop but does not over rule the actually physically stopped clock such that it continues to accumulate time.

Please remember the facts of this case. "A" (via the built in timers) physically stopped his clock at the predicted relavistic view from "A's" frame at 4.359 hours. You CANNOT now claim that the clock will continue to accumulate time and read any other number because of simultaneity.

Or do you think that Clock B does not have an altered perspective to Clock A?

B certainly has an altered perspective of A's clock. Glad to see you use the term perspective.

 

[MacM]

Keep looking.
One is tempted to conclude that your feeling of something not being right is due to your bias against the SR model - and nothing more.

Not at all. If you have digested the sketch of Reciprocity you would see why.

 

[Pete]

See my sketch on Reciprocity.

I think your concept of reciprocity is flawed; it only applies in symmetrical situations.

No. I am saying that the idea of simultaneity means he thinks his clock should not have stopped - but infact it does. Not that the clock stopped in "A's" frame actually continues to run because B sees a different simultaneity. Simultaneity only suggests to B as to when his clock should stop but does not over rule the actually physically stopped clock such that it continues to accumulate time.

Please remember the facts of this case. "A" (via the built in timers) physically stopped his clock at the predicted relavistic view from "A's" frame at 4.359 hours. You CANNOT now claim that the clock will continue to accumulate time and read any other number because of simultaneity.

I think you're missing the point.

We have two specific events:
Clock A stops.
Clock B stops.

From A's perspective, those events are simultaneous.
From B's perspective, those events are not simultaneous.

All agree that B stops when it reads 35820 seconds.
All agree that A stops when it reads 36000 seconds.

Where's the problem?

B certainly has an altered perspective of A's clock. Glad to see you use the term perspective.

"Perspective" does not mean "perception".

 

[Pete]

There's something else which might or might not be relevant to you.

In this diagram:
<img src="/attachment.php?attachmentid=3349&stc=1">
We're looking at the situation from A's perspective... but that perspective applies to all objects that are stationary with respect to A.
An observer stationary with respect to A would draw the same conclusions about the timing of the light flashes no matter what their location.

This illustrates that alterations to simultaneity aren't simply due to some signal transmission delay.

 

[MacM]

I think your concept of reciprocity is flawed; it only applies in symmetrical situations.

Not so. IF you have a reversable sequence, symmetrical or not, Reciprocity produces the same result.

I think you're missing the point.

We have two specific events:
Clock A stops.
Clock B stops.

So ask yourself this. If "A" expects "B" via relativistic calculations to read a given recorded accumulated time of 4.359 hours when its clock is at 10 hours and B clock stops at that number and "A" reads 10 hours, did they stop simultaneously or not?

You seem to be using simultaneity to wash away any physical relationships between clocks, including relativity of the readings!

From A's perspective, those events are simultaneous.

Agreed.

From B's perspective, those events are not simultaneous.

I disagree but that is irrelevant. "B" is stopped at the correct time to satisfy "A's" relavistic view. IT IS NO LONGER RUNNING. It does not and cannot continue to change recorded times. If it does not read 4.359 hours then Relativity is incorrect regarding "A's" view of what the clock should read.

Being stopped at 4.359 hours "B", by relavistic time dilation expects "A" to only read 1.9 hours. That is shown to not be the case.

All agree that B stops when it reads 35820 seconds.

How did you arrive at this number? "A" stopped the clock (via my timer built into the clock, at its calculated relavistic value of 4.359 hours = 15,692 seconds. Just how have you caused a "Stopped" clock to continue to accumulate time?

Having been physically stopped by "A" at its appropriate relavistic time (simultaneously with "A" reading 10 hours - IF Relativity is valid) then after its 4.359 hours of operation believes relavistically that "A" should read 1.9 hours = 6,840 seconds. It doesn't it reads 10 hours.

All agree that A stops when it reads 36000 seconds.

Where's the problem?

The problem is either Relativity is invalid to conclude "B" will read 4.359 hours or Relativity is wrong to conclude B's view of "A" is 1.9 hours.

"Perspective" does not mean "perception".

Agreed but getting closer. According to Webster only 1 out of 6 definitions refer to it as being a true vision.

 

[MacM]

There's something else which might or might not be relevant to you.

In this diagram:
<img src="/attachment.php?attachmentid=3349&stc=1">
We're looking at the situation from A's perspective... but that perspective applies to all objects that are stationary with respect to A.
An observer stationary with respect to A would draw the same conclusions about the timing of the light flashes no matter what their location.

This illustrates that alterations to simultaneity aren't simply due to some signal transmission delay.

Reciprocity would be the view from B. Then compare the results. You will find they are equal but reversed.

 

[Pete]

Reciprocity would be the view from B. Then compare the results. You will find they are equal but reversed.

No - we found that the results were *not* reversed.

This is clearly worked through starting with [post=694446]this post[/post].
You say you can't see a problem with it. It is not a difficult scenario.

 

[Pete]

IF you have a reversable sequence, symmetrical or not, Reciprocity produces the same result.

Prove it.

 

[Pete]

did they stop simultaneously or not?

Am I far, or not?

Simultaneity depends on frame of reference (perspective, if you will), remember.

In one frame of reference (A's), they stopped simultaneously.