The Twin Paradox & Frame of Reference

[swansont]

Stop nitpicking.

A frame determines which events an observer considers happening simultaneously. They all have same time coordinate. Didn't you know that?

In my spacetime diagram the event clock P showing 11:00, and Andromeda clock showing 13:00 happen simultaneously per purple frame.

 

 

What you think is wrong. In fact you tell me you cannot read spacetime diagrams nor what they stand for.

 

Will be seen to be? I'm not talking about when an event is literally SEEN by an observer. I talk about when an event happens for an observer. You should know the difference, don't you?

To quote something I read recently, stop nitpicking.

 

Once more: I'm not talking about SEEING a clock run backwards. Granpa deals with a clock running backwards per observer's frame. Sure you know the difference. Don't you?

 

Same time coordinate means happening simultaneously. Whatever the time indication on the clock is. Clock P showing 11:00, and Andromeda clock showing 13:00 happen simultaneously per purple frame. Both events have same time coordinate per purple frame.

Having the 1100 clock signal from P arrive at the same time as the 1300 clock signal from Andromeda is a different claim than saying that a clock ran backwards. That was the claim, and that's what I'm dealing with. The 1100 signal from P still arrives before the 1101 signal, and so on. The reading doesn't go backwards. If you're not talking about seeing a clock run backwards, you're in the wrong thread.

[DimaMazin]

 

Stop nitpicking.

A frame determines which events an observer considers happening simultaneously. They all have same time coordinate. Didn't you know that?

In my spacetime diagram the event clock P showing 11:00, and Andromeda clock showing 13:00 happen simultaneously per purple frame.

 

 

What you think is wrong. In fact you tell me you cannot read spacetime diagrams nor what they stand for.

 

Will be seen to be? I'm not talking about when an event is literally SEEN by an observer. I talk about when an event happens for an observer. You should know the difference, don't you?

 

 

Once more: I'm not talking about SEEING a clock run backwards. Granpa deals with a clock running backwards per observer's frame. Sure you know the difference. Don't you?

Same time coordinate means happening simultaneously. Whatever the time indication on the clock is. Clock P showing 11:00, and Andromeda clock showing 13:00 happen simultaneously per purple frame. Both events have same time coordinate per purple frame.

Simultaneity can not be visible on distance, clock indication can. You can calculate simultaneity goes backwards on clock indication,but you can't see clock runs backwards.

[VandD]

To quote something I read recently, stop nitpicking.

 

Having the 1100 clock signal from P arrive at the same time as the 1300 clock signal from Andromeda is a different claim than saying that a clock ran backwards. That was the claim, and that's what I'm dealing with. The 1100 signal from P still arrives before the 1101 signal, and so on. The reading doesn't go backwards. If you're not talking about seeing a clock run backwards, you're in the wrong thread.

 

I think YOU are in the wrong thread. In Granpa's chart (post#5) - see below- he didn't say anything about seeing the clock running bacwards. YOU critisized him by stating one cannot SEE the clock running backwards. But that's off topic.

And from then onwards you continued critisizing his chart, probably -I guess- because you don't understand what his chart says.

I showed in my spacetime diagram what Granpa's 'clock running backwards' means.

 

Edited July 13, 2016 by VandD

[swansont]

"Some even seemed to run backwards"

 

No.

 

And neither of you have presented any math to show that this would be the case. "See" vs "seem" to me is a distinction without a difference in this case. You can't say anything about the clock without looking at it.

[granpa]

He even drew you a space time diagram.

My guess is that you are hoping to make us angry so we will say something bitter and then you can get us banned

Edited July 13, 2016 by granpa

[VandD]

"Some even seemed to run backwards"

 

No.

 

And neither of you have presented any math to show that this would be the case. "See" vs "seem" to me is a distinction without a difference in this case. You can't say anything about the clock without looking at it.

Clever. But it won't help you.

Based on what you see, you know what happened at a spacelike distance.

Let's take a simple case: Einstein's train thought experiment, famliliar to all relativity experts, so I don't need to draw a spacetime diagram.

The light signal from both light flashes reach the embankment observer at the same moment. But the light flashes don't reach the train observer at the same moment.

Newton speaking one would say: for the train observer both flashes occur simultaneously too, but the light signals do not reach him at the same time.

But Einstein teached us that for the train passenger (per his frame) both flashes didn 't happen simultaneously. I.o.w. when the train observer passes the embankment observer, the front flash already occured, but the rear flash still has to happen.

If the front and rear clock indicate 12:00 when the flashes hit the clocks (which is the case for train observer AND embankment observer, because events itself are absolute), the train observer, per his frame, none of those two events happen (are part of his 3D reality of events happening 'now' ) when he passes the embankment observer. For the train observer the rear clock shows a time less than 12:00, the front clock a time beyond 12:00. No flashes.

 

Train observer and embankment observer consider a different 3D world of simultaneous events, but share one and the same 4D spacetime. Remember some Einstein quotes about 4D existence:

 

<< From a "happening" in three-dimensional space, physics becomes, as it were, an "existence" in the four-dimensional "world". >> (Albert Einstein. "Relativity: The Special and the General Theory." 1916. Appendix II Minkowski's Four-Dimensional Space ("World") (supplementary to section 17 - last section of part 1 - Minkowski's Four-Dimensional Space).

<< Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence. >> (Albert Einstein, "Relativity", 1952).

 

<<...for us convinced physicists the distinction between past, present, and future is only an illusion, although a persistent one." >> ( Letter to Michele Besso family, March 21, 1955. Einstein Archives 7-245).

Karl Popper about his encounter with Einstein:

<< The main topic of our conversation was indeterminism. I tried to persuade him to give up his determinism, which amounted to the view that the world was a four-dimensional Parmenidean block universe in which change was a human illusion, or very nearly so. He agreed that this had been his view, and while discussing it I called him "Parmenides".... >> (Karl Popper, Unended Quest: An Intellectual Autobiography.Routledge Classics. Routledge. pp.148–150).

Edited July 13, 2016 by VandD

[swansont]

Clever. But it won't help you.

Based on what you see, you know what happened at a spacelike distance.

Let's take a simple case: Einstein's train thought experiment, famliliar to all relativity experts, so I don't need to draw a spacetime diagram.

The light signal from both light flashes reach the embankment observer at the same moment. But the light flashes don't reach the train observer at the same moment.

Newton speaking one would say: for the train observer both flashes occur simultaneously too, but the light signals do not reach him at the same time.

But Einstein teached us that for the train passenger (per his frame) both flashes didn 't happen simultaneously. I.o.w. when the train observer passes the embankment observer, the front flash already occured, but the rear flash still has to happen.

If the front and rear clock indicate 12:00 when the flashes hit the clocks (which is the case for train observer AND embankment observer, because events itself are absolute), the train observer, per his frame, none of those two events happen (are part of his 3D reality of events happening 'now' ) when he passes the embankment observer. For the train observer the rear clock shows a time less than 12:00, the front clock a time beyond 12:00. No flashes.

 

 

And what does this have to do with a clock seeming to run backwards? It's a simultaneity issue, not a clock reading issue. You don't have to look at a clock to see if something is simultaneous, but you do if you have anything to say about how fast, or what direction, it's running

[VandD]

 

And what does this have to do with a clock seeming to run backwards?

I hoped you would understand the front and rear clock I talked about stand respectively for the P clock and Andromeda clock of my spacetime diagram. All you had to do then is add acceleration from enbankment frame (or train frame when train is at rest) to train/rocket frame relative moving in order to to grasp the backwards running of clock P and faster running of Andromeda clock. Unfortunately that was wishful thinking. Sorry about that.

 

I wonder what your position is about the Andromeda clock rate per rocket frame. Would you accept the Andromeda clock runs faster per rocket frame during rocket acceleration?

If you don't accept clock P runing backwards per rocket frame, then you won't accept Andromeda clock running faster per rocket frame during rocket acceleration either. This means you don't understand, and/or won't accept frame rotation during acceleration (and deceleration). Agreed?

[imatfaal]

VandD - trying to get head around what you are saying. In your space time diagram explanation what exactly are the rocketbased scientists observing?

 

When they are at rest with respect to p,earth, and andromeda you state that they all in sync with time 12:00 - is this something they take on faith, communicate with colleagues, or observe? It seems from your explanation of your diagram that you contend after acceleration at 1201 (rocket time) that P clock has (during the acceleration which has now ceased) run backwards and is at some time shortly after 1100 - how is this known by observation? calculation? Similarly that at 1201 rocket time Andromeda clock is ticking at a bit after 13:00 - again what is this observation? calculation? signal reception?

 

thanks for clarifying

[granpa]

https://en.wikipedia.org/wiki/Einstein_synchronisation

[VandD]

VandD - trying to get head around what you are saying. In your space time diagram explanation what exactly are the rocketbased scientists observing?

 

When they are at rest with respect to p,earth, and andromeda you state that they all in sync with time 12:00 - is this something they take on faith, communicate with colleagues, or observe? It seems from your explanation of your diagram that you contend after acceleration at 1201 (rocket time) that P clock has (during the acceleration which has now ceased) run backwards and is at some time shortly after 1100 - how is this known by observation? calculation? Similarly that at 1201 rocket time Andromeda clock is ticking at a bit after 13:00 - again what is this observation? calculation? signal reception?

 

thanks for clarifying

 

This must be a joke! You relativity guys apparently never understood any sloped x' axis in a Minkowski spacetime diagram? I'm speechless.

 

The frame of the train/rocket observer is a sloped x' axis in a Minkowski diagram.

Why?

Because it connects different events than the x-axis of the embankment observer.

Why?

Because of relativity of simultaneity (we talk special relativity, or not?). Events that are/happen/exist simultaneously for the train observer are not the same events as the collection of events that happen/exist simultaneousy for the embankment observer.

Do I now have to clarify where relativity of simultaneity come from? Analyzing Einstein train thought experiment might help as a shortcut.

[swansont]

I hoped you would understand the front and rear clock I talked about stand respectively for the P clock and Andromeda clock of my spacetime diagram. All you had to do then is add acceleration from enbankment frame (or train frame when train is at rest) to train/rocket frame relative moving in order to to grasp the backwards running of clock P and faster running of Andromeda clock. Unfortunately that was wishful thinking. Sorry about that.

Recasting an argument by only changing the labels and thinking that the underlying explanation has somehow changed is wishful thinking.

 

I wonder what your position is about the Andromeda clock rate per rocket frame. Would you accept the Andromeda clock runs faster per rocket frame during rocket acceleration?

If you don't accept clock P runing backwards per rocket frame, then you won't accept Andromeda clock running faster per rocket frame during rocket acceleration either. This means you don't understand, and/or won't accept frame rotation during acceleration (and deceleration). Agreed?

 

Telling me what I must agree to is a losing proposition. The opposite case of a clock running faster is another clock running slower, not backward. So thanks for the false dichotomy, but I'll pass.

 

Here's the problem as I see it. for a clock to seem to run backward, we have to get a signal from it indicating the time, and then get another, indiciating an earlier time. Then we'd have to get the original signal all over again. Nobody has come close to showing that this is the case, and whoever claims that the clocks seem to run backwards won the burden of proof.

 

So lets take the example you have provided. If planet P is more than 1 hour away from earth, then when the rocket accelerates at noon, it hasn't even gotten the 1100 ping from the planet. So how can you claim anything ran, or appeared to run, backwards?

 

If they are closer than 1 light hour away, then the 1100 ping has already arrived. Does it arrive again? How?

 

Show me the math.

 

This must be a joke! You relativity guys apparently never understood any sloped x' axis in a Minkowski spacetime diagram? I'm speechless.

 

The frame of the train/rocket observer is a sloped x' axis in a Minkowski diagram.

Why?

Because it connects different events than the x-axis of the embankment observer.

Why?

Because of relativity of simultaneity (we talk special relativity, or not?). Events that are/happen/exist simultaneously for the train observer are not the same events as the collection of events that happen/exist simultaneousy for the embankment observer.

Do I now have to clarify where relativity of simultaneity come from? Analyzing Einstein train thought experiment might help as a shortcut.

 

 

The claim that a clock seems to run backwards is not an issue of the relativity of simultaneity.

[VandD]

Recasting an argument by only changing the labels and thinking that the underlying explanation has somehow changed is wishful thinking.

 

 

Telling me what I must agree to is a losing proposition. The opposite case of a clock running faster is another clock running slower, not backward. So thanks for the false dichotomy, but I'll pass.

 

Here's the problem as I see it. for a clock to seem to run backward, we have to get a signal from it indicating the time, and then get another, indiciating an earlier time. Then we'd have to get the original signal all over again. Nobody has come close to showing that this is the case, and whoever claims that the clocks seem to run backwards won the burden of proof.

 

So lets take the example you have provided. If planet P is more than 1 hour away from earth, then when the rocket accelerates at noon, it hasn't even gotten the 1100 ping from the planet. So how can you claim anything ran, or appeared to run, backwards?

 

If they are closer than 1 light hour away, then the 1100 ping has already arrived. Does it arrive again? How?

 

Show me the math.

 

 

The claim that a clock seems to run backwards is not an issue of the relativity of simultaneity.

 

Hopeless. You don't want to accept/understand any sloped x'-axis in a Minkowki diagram. Big problems.

Edited July 14, 2016 by VandD

[granpa]

Recasting an argument by only changing the labels and thinking that the underlying explanation has somehow changed is wishful thinking.

 

 

 

Telling me what I must agree to is a losing proposition. The opposite case of a clock running faster is another clock running slower, not backward. So thanks for the false dichotomy, but I'll pass.

 

Here's the problem as I see it. for a clock to seem to run backward, we have to get a signal from it indicating the time, and then get another, indiciating an earlier time. Then we'd have to get the original signal all over again. Nobody has come close to showing that this is the case, and whoever claims that the clocks seem to run backwards won the burden of proof.

 

So lets take the example you have provided. If planet P is more than 1 hour away from earth, then when the rocket accelerates at noon, it hasn't even gotten the 1100 ping from the planet. So how can you claim anything ran, or appeared to run, backwards?

 

If they are closer than 1 light hour away, then the 1100 ping has already arrived. Does it arrive again? How?

 

Show me the math.

 

 

 

The claim that a clock seems to run backwards is not an issue of the relativity of simultaneity.

It isn't just what you see when you look in the direction of the clock.

You also have to calculate the distance to the clock. That distance will change when you accelerate.

Edited July 14, 2016 by granpa

[Phi for All]

 

Hopeless. You don't want to accept/understand any sloped x'-axis in a Minkowki diagram. Big problems.

 

!

Moderator Note

This approach, where you climb on a high horse to avoid the flood of requests for evidence, and hurl insults instead of meaningful discussion or supportive maths is not going to be appreciated here at all. I would suggest you reset your attitude for receptiveness and cooperation. This is a science discussion forum.

 

There's no need for you to respond to this. This isn't a request, or something you get an opinion on. Start being civil and following the rules you agreed to when you joined. If you object to this note, please use the Report Post feature.

[swansont]

You also have to calculate the distance to the clock. That distance will change when you accelerate.

 

 

So do the calculation and demonstrate what you have claimed. Nothing anybody has said explains how one light signal can overtake another, which is what is required here.

 

The only thing I can think of that matches your claim is that the expected arrival time of a clock signal needs to be adjusted when you accelerate. That's the only thing that fits in with simultaneity — a signal didn't arrive when you thought it might when you don't account for the fact that relativity is real. But at no time do you get any kind of signal that indicates a clock ran backwards, and your calculations wouldn't be off if you accounted for relativity.

 

If your point this whole time was that if you ignore the effects of relativity you will get the wrong answer...well, yes, that's true, but not very enlightening. Nor was it clearly expressed.

[granpa]

1 light signal does not have to overtake another. That is what I just explain to you. The distance to the clock changes when you accelerate. Therefore your calculation of the current time on that clock changes. Even though what you are seeing does not change.

[swansont]

1 light signal does not have to overtake another. That is what I just explain to you. The distance to the clock changes when you accelerate. Therefore your calculation of the current time on that clock changes. Even though what you are seeing does not change.

 

 

The calculation changes. Not the clock.

[granpa]

Yes. So? Please read my signature

 

For those people that have turned signatures off, my signature reads:

In relativity, reality doesnt change just because you change velocity. Only your perspective on that reality changes.

Edited July 14, 2016 by granpa

[Endy0816]

Events will always be progressing in the forward direction though.