[guest39538]

http://home.earthlink.net/~owl232/twinparadox.pdf

This is worth a read.

''According to STR, different intertial reference frames (RF’s) can disagree on the time that
elapses between two events, as well as on the length of an object. These discrepancies are
described by the Lorentz Transformation equations:''


No they can't disagree on length of an object or disagree on the elapsed time between events,


They can agree the visual length angle of light is different to give an illusion of a different length object and agree that their measurements of time are different and their clocks are not synchronised constants.

[saspinski (OP)]

http://home.earthlink.net/~owl232/twinparadox.pdf

This is worth a read.

It is well written, avoiding answers like "the traveller twin knows that he accelerates" or "it is a problem for GR because there is at least one change of speed direction".

But he could find a define answer because one twin remains on earth surface, always an inertial reference frame. The other has two inertial reference frame, one when he is going away and other when return.  Choosing any of that three RF, the traveller twin returns younger, applying the Lorenz tranformations for time.

But if both are traveller twins, each one going away from earth to opposite directions, and then returning, that asymmetry disappears. A supposed third twin (or triplet) staying on earth, could agree that the traveller ones came back younger, but not one of the travellers regarding his (also travelling) brother.

[saspinski (OP)]

In the morning of the next day after my last post, I thought of a solution:

Based on the article of the link (http://home.earthlink.net/~owl232/twinparadox.pdf), the calculations have to be made for just one inertial reference frame for all the jorney. Any of them are acceptable.

When one of the triplets travels out from earth, and starts monitoring his brother ship going to the opposite direction, he can use his own RF, so he is not moving. The other ship is travelling fast, so his brother is aging slowly for him.

After reaching the return point, he changes direction and come back. Now, he must keep using the same RF, (his ship while it was travelling from earth to the return point). By the way, that is now precisely the RF of his brother, because he was travelling to the opposite direction and are returning to earth.

So, his brother is not moving now, and he is travelling fast. So he is aging quickly than his brother.

After meeting on earth, both will have the same age, and as shown in the link, younger than the third brother, that remained home.

[PhysBang]

Two twins on earth measure the expansion of the universe and determine the redshift of light for selected galaxies. Then one twin goes on a space flight at close to the speed of light to a distant planet. Both twins carry on measurements of their selected galaxies. While the earthbound twin gets the predicted results the journeying twin finds the galaxies redshifted directly behind and blue shifted in front. From this he can determine he is in motion. Therefore both twins can determine who will be time dilated and age more slowly. Thus when they meet up again they won't be surprised at the age difference. No paradox.

This doesn't work because the Earth is in motion relative to the CMB average, but the twin scenario still works.

The "answer" to the is non-paradox is that the situation is not symmetric. The one twin does not have one inertial reference frame; this is required for the twin to turn around and come back.

[PhysBang]

http://home.earthlink.net/~owl232/twinparadox.pdf

This is worth a read.

''According to STR, different intertial reference frames (RF’s) can disagree on the time that
elapses between two events, as well as on the length of an object. These discrepancies are
described by the Lorentz Transformation equations:''


No they can't disagree on length of an object or disagree on the elapsed time between events,


They can agree the visual length angle of light is different to give an illusion of a different length object and agree that their measurements of time are different and their clocks are not synchronised constants.

You are 100% wrong.

[Alan McDougall]

http://home.earthlink.net/~owl232/twinparadox.pdf

This is worth a read.

''According to STR, different intertial reference frames (RF’s) can disagree on the time that
elapses between two events, as well as on the length of an object. These discrepancies are
described by the Lorentz Transformation equations:''


No they can't disagree on length of an object or disagree on the elapsed time between events,


They can agree the visual length angle of light is different to give an illusion of a different length object and agree that their measurements of time are different and their clocks are not synchronised constants.

You are 100% wrong.

All theories are 100% wrong unless they are 100% correct. 

No, you are wrong, present information may say I am wrong by their subjective thinking, but my objective thinking says that they are wrong, so who's thinking is correct?

Answer = neither of us, because it is both subjective to our thoughts,

The objective reality which you call the subjective reality, is different to the subjective reality you call the objective reality. It is not me who has it backwards according to definition.


Subjective - influenced by the mind or personal feelings /  belief


Objective - uninfluenced by personal feeling or belief,   (that which I use)

It is a misnomer  to call it a paradox because in reality both twins in their respective time frames are moving into the future.

[granpa]

I have found the question below in an old thread about the twin paradox. I could not get an answer at that thread or from other sources. The problem for me is: if the situation is totally simmetric, both twins return at the same age. But isn't it against SR theory?
I assume that all acelerations and desacelarations are the same for both the traveller twins, so GR should not explain any difference.

Things get interestinger when you have triplets, one stays on the ground, one goes off in a spacecraft to the celestial north, the other off to the celestial south, and both later return. What are their relative ages, and why?

https://commons.wikimedia.org/wiki/File:Twin_paradox.png

[hamdani yusuf]

I have found the question below in an old thread about the twin paradox. I could not get an answer at that thread or from other sources. The problem for me is: if the situation is totally simmetric, both twins return at the same age. But isn't it against SR theory?
I assume that all acelerations and desacelarations are the same for both the traveller twins, so GR should not explain any difference.

Things get interestinger when you have triplets, one stays on the ground, one goes off in a spacecraft to the celestial north, the other off to the celestial south, and both later return. What are their relative ages, and why?

https://commons.wikimedia.org/wiki/File:Twin_paradox.png

how can someone in the rocket see the clocks run backward without moving faster than light?
photons arranged to show prior to 12:00 have already pass the rocket, so to see them again, the rocket must catch them up faster than photon's speed.

[granpa]

Draw A Spacetime diagram. Let the x-axis a space and the y-axis be time. Draw clocks on the x-axis at time equals zero.

Then draw a diagonal line representing 1 simultaneous moment from the point of view of the rocket.



How to draw a spacetime diagram:
https://www.physicsforums.com/threads/how-to-draw-a-spacetime-diagram.314080/

[hamdani yusuf]

Draw A Spacetime diagram. Let the x-axis a space and the y-axis be time. Draw clocks on the x-axis at time equals zero.

Then draw a diagonal line representing 1 simultaneous moment from the point of view of the rocket.



How to draw a spacetime diagram:
https://www.physicsforums.com/threads/how-to-draw-a-spacetime-diagram.314080/

IMO, a clock can be said to run backward if at one instance it shows a particular time reading, and then later on, the same clock shows the reading of time prior to that instance. For example, at start a clock shows 12:00, but later on, it shows 11:59.
Your spacetime diagram doesn't show this case.

[granpa]

When the rocket is stationary then 1 simultaneous moment now is represented by the x-axis. When they work it starts moving then the line representing one one moment now becomes a dog and a lion. The faster the Rock and moves them or Tilted the line is. You can obviously see that Clark's further away will seem to be more out of sync. Just consider the case of a park that is millions or billions of light-years away from the rocket. Consider how far out of sync it must become.

[IAMREALITY]

When the rocket is stationary then 1 simultaneous moment now is represented by the x-axis. When they work it starts moving then the line representing one one moment now becomes a dog and a lion. The faster the Rock and moves them or Tilted the line is. You can obviously see that Clark's further away will seem to be more out of sync. Just consider the case of a park that is millions or billions of light-years away from the rocket. Consider how far out of sync it must become.

Not a clue what you just tried to say.

What I do know, is that the theory above is wrong.  Under no circumstance in physics would the clock on the left suddenly be 11:59 unless almost 24 hours has elapsed and it's showing the time for the next day.  But no, a clock that once read 12:00 am will under no circumstances tick backwards to 11:59, no matter what you do.  Period.

[granpa]

I didn't say it would take backwards. I said from the point of view of the rocket it would seem to be.

[IAMREALITY]

I didn't say it would take backwards. I said from the point of view of the rocket it would seem to be.

Wouldn't that mean they would see 11:59?  That's what your diagram shows.  but if they left when it was synchronized at 12, it's an impossibility for it to then show 11:59, which would in fact be ticking backwards.

The point of view of the rocket could never see any of the clocks show anything prior to 12 am, if they started at 12 am.

[granpa]

 What would a o'clock at infinity say from the Rockets point of view? What would a o'clock at negative infinity say?

[IAMREALITY]

What would a o'clock at infinity say from the Rockets point of view? What would a o'clock at negative infinity say?

It would say "warning: fatally flawed logic ahead".

Stick to what we're talking about.  Which is a bunch of clocks starting at 12 am and how it's impossible for the rocket to ever see a time prior to 12 am on them, regardless of your diagram saying otherwise. 

[granpa]

So you don't believe what a simple space-time diagram is telling you?

[IAMREALITY]

So you don't believe what a simple space-time diagram is telling you?

You mean the patently false diagram?  No.

[PhysBang]

What would a o'clock at infinity say from the Rockets point of view? What would a o'clock at negative infinity say?

It would say "warning: fatally flawed logic ahead".

Stick to what we're talking about.  Which is a bunch of clocks starting at 12 am and how it's impossible for the rocket to ever see a time prior to 12 am on them, regardless of your diagram saying otherwise.

You are confusing what one way of creating a system of coordinates might assign to the time of an event with what another way of creating a system of coordinates might assign to an event with what any particular clock might say at a particular event. Not every clock is synchronized.

[IAMREALITY]

What would a o'clock at infinity say from the Rockets point of view? What would a o'clock at negative infinity say?

It would say "warning: fatally flawed logic ahead".

Stick to what we're talking about.  Which is a bunch of clocks starting at 12 am and how it's impossible for the rocket to ever see a time prior to 12 am on them, regardless of your diagram saying otherwise.

You are confusing what one way of creating a system of coordinates might assign to the time of an event with what another way of creating a system of coordinates might assign to an event with what any particular clock might say at a particular event. Not every clock is synchronized.

No idea what on earth you just tried to say. 

What I know, is if the clocks displayed 12am when the rocket left, no event on the rocket would allow them to see 1157,as the diagram shows.