[CPT ArkAngel]

SR is a consistent theory according to its limitations and postulates. I agree. There is no reason for me to argue beyond that in this discussion. I am sure some readers understood what I meant. There is no point of arguing when someone continuously misinterpret your arguments by making imaginary extensions to them.

My end point is that there is a more complete explanation to find for time dilation. The quest for a unified theory passes by a single explanation for time dilation. People tend to stick too much within SR and forget that it is only true within strong limitations. Some of them are limitations that the real universe doesn't have. If you disagree with that, this is where my point of view is irreconcilable with yours. If you understand this point of view, you can understand all my statements, if not, you just can't! The other thing to understand is that the choice of validation of SR with "inertial frame" only is an apriori choice. This choice produces the asymmetry of the twin paradox. This is consistent with Pete explanations and it is what I meant by emphasizing on the symmetry of astronaut A meeting astronaut B having a constant relative speed. Nothing more.

[PhysBang]

SR is a consistent theory according to its limitations and postulates. I agree. There is no reason for me to argue beyond that in this discussion. I am sure some readers understood what I meant. There is no point of arguing when someone continuously misinterpret your arguments by making imaginary extensions to them.

Dude, why write things that are so obviously untrue.

I'll repeat...

You wrote, "All explanations within the frame of SR alone are wrong because there is no key to differentiate the twins." That's simply false, as many citations above have established.

You wrote, "The change is associated to the twin in the rocket by a purely arbitrary a priori choice." That is also false, because even the twin in the rocket knows that she changed direction.

You wrote, "There are no explanations concerning acceleration and inertia in SR." This is also false, because every textbook that deals with SR covers acceleration.

You wrote, "In Special Relativity, the acceleration is entirely reciprocal for both twins." That is false because, again, if we are to include acceleration, the acceleration for one twin is different because she changes direction according to her own initial trajectory.

You wrote, "SR is not just an add on to Newtonian mechanics, it is the start of a new theory." And while it is true that SR is in some sense a new theory, it begins with the assumption of Newtonian mechanics.

You wrote, "With SR alone, you cannot really explain why the accelerating frame will have a slower time." And there are various demonstrations that this claim is false.

My end point is that there is a more complete explanation to find for time dilation. The quest for a unified theory passes by a single explanation for time dilation. People tend to stick too much within SR and forget that it is only true within strong limitations.

But the point of trying to claim that there is a twin "paradox" is that there is some problem when we consider SR only. This is essential to understanding the scenario.You not only refuse to consider SR alone, you refuse to actually consider SR.

The other thing to understand is that the choice of validation of SR with "inertial frame" only is an apriori choice. This choice produces the asymmetry of the twin paradox.

But the choice isn't arbitrary: we are not free to consider either twin to be not moving, one is moving by definition and SR has an exact way to represent this.

[hamdani yusuf]

The 'twins' explanation #14 using the axis of simultaneity is extraneous fluff. That convention only assigns times to events observed locally, since a system of clocks would be logistically impossible for astronomical distances. The distant events result from the behavior of the remote clock and aren't altered by the simultaneity convention.

twins-3 seg.gif (2.66 kB . 203x416 - viewed 9712 times)
Using the notation (x, t) and fig.2,
A records B leaving (0, 0) a .6c, and returning (0, 10).
B records A leaving (0, 0) at .6c, and returning (0,t= .
Does the accumulated time differ?
A experienced 10 flashes, all observed by B.
B experienced 8 flashes, all observed by A.
B is younger than A.
Within the closed course, there are no missing events.
The reversal data is irrelevant.
The perceived doppler shifts for the diverging vs converging segments is irrelevant.
The instantaneous reversal by B is irrelevant, since it's duration is zero time, i.e. equivalent to "it never happened", thus not having any catastrophic results. The discontinuity is equivalent to two B frames participating in the experiment.
There is no acceleration/*deceleration involved, just inertial motion.
* Yes, there is such a word, for those too lazy to use a dictionary.

Your diagram shows that A and B send and receive the same number of signal, which would mean that in the end they have the same age.

[hamdani yusuf]

What do you think about this explanation?

Imagine if along rocket trajectory we install synchronized clock at every 1 light second. The rocket also bring a clock which is already synchronized before the journey.
When the twin in rocket is passing each clock on the way, what time do they read, and what time shown by his own clock for each passing?

[yor_on]

as a pure byside Yusuf (presuming this your forename, correct me if I'm wrong:) synchronizing 'clocks' is a possibility, but it won't tell us a 'universal time'. Just that those two clocks share a same 'frame of reference' at some original point of place. To define clocks at for example different elevation as 'synchronized' is a no no the way I think about it. Even though one could set them to a same time, they would start to deviate after a while. And so it is with relative speeds too. No way to find a absolute time for anything, just correlations in time and space.

[hamdani yusuf]

as a pure byside Yusuf (presuming this your forename, correct me if I'm wrong:) synchronizing 'clocks' is a possibility, but it won't tell us a 'universal time'. Just that those two clocks share a same 'frame of reference' at some original point of place. To define clocks at for example different elevation as 'synchronized' is a no no the way I think about it. Even though one could set them to a same time, they would start to deviate after a while. And so it is with relative speeds too. No way to find a absolute time for anything, just correlations in time and space.

You can call me Dani. Just Dani Okay?
I meant six clocks in the same frame of reference, i.e. clock on earth, clock at 1, 2, 3, 4, and 5 light seconds away from earth. They are stationary relative to each other, so after synchronized, they should tick at the same rate.
- When the rocket twin start moving, his clock should show the same value as the earth clock, which is 0 second.
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 5 light second location?
The rocket then turn around. Is there something interesting happens to his clock?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is coming back to earth?

[yor_on]

Depends on velocity of the rocket. That is if you define the clocks you placed out as 'synchronized with earths clock aka being in a same frame of reference'. But it also depends on the gravitational 'field/potential' of that 'earthly clock' relative clocks placed in another gravitational potential, aka 'space'. So there will be no real synchronization done, unless we assume the gravitational potentials being the same, aka all clocks synchronized in a 'same frame of reference'
=

Eh Dani, using 'velocity' as I'm thinking of you using both a speed and a direction for passing those other clocks :) Otherwise 'speed' should be the correct expression for it, furthermore I'm assuming acceleration, but maybe you're thinking of it in form of the acceleration already done so that the ship just 'coast' (uniform motion) past those clocks? If you want to prove your thoughts not using a acceleration you should eliminate Earth and just use the clocks,, a rockets uniform motion and 'space', eliminating gravity as far as possible. The way that is done normally is using 'test particles' as I understands it.

[hamdani yusuf]

Implicit assumption when dealing with pure special theory of relativity is that gravity effect is negligible.
To make it simpler, we can replace earth with a free floating space ship.

[yor_on]

Hmm seems we wrote past each other. I was adding some thoughts to the text as you wrote

[bandtank]

The fundamental issue with CPT's point of view is a lack of evidence. This isn't my area of expertise, but I was taught the basics of SR and GR in engineering classes and acceleration was only mentioned verbally, not mathematically. I have lost the ability to manipulate numbers and equations with respect to problems such as this, but the general explanation offerd by PhysBang aligns quite well with the intuitive understanding I acquired from the aforementioned classes. Also, it just makes sense.

CPT - if you can provide a reference, you should do so. Multiple links have been posted with credible information to refute your position, but you've only expressed your opinions without any factual support. I tried looking for the statements you suggested I would easily find all over the internet and I found exactly zero that adopted or supported your position. As my man big willy said, put up or shut up.

[yor_on]

Actually nothing is simple as soon as we pass idealized testparticles in a vacuum so small that you can presume gravity to be negligible for your question Dani. I've been wondering about it before and it's easy to see why one would use that description. As soon as you introduce a mass then there will be gravity acting and being acted on. So any clock inside that ship will be acted upon by mass (the ship and whatever other gravity that may exist) and in its turn act upon whatever other mass/gravity there is.

The best example I know of, and the simplest, is 'light clocks' moving at different uniform motions. The explanation given to why we then see them 'tick' differently depending on relative motion is due to the geometry for the light bouncing between the mirrors. the 'distance' it has to travel between those mirrors from the far away observers point of view. You sitting on one shouldn't experience this as you ideally/theoretically then would belong to the same 'frame of reference'. And that follows from the fact that all uniform motions, locally described, are the same. You can't differ between them locally, only when comparing your 'frame of reference' to someone else are uniform motions existent.
=

I better add that even though it is the simplest it's just a analogy. It's not totally satisfactorily to me as if it was the geometry alone that defined it those mirrors rotated another direction would present us with a red shift. But geometrically I think it would hold then too as the distance traveled by this '[ bouncing light ] /clock' should be the same, as defined from the far away observers observation. for the local observer there is no 'motion' existent, unless he defines some stellar object as being 'still', which requires him to prove that it is. In a black box which is a crucial thought evidence/experiment relative motion doesn't exist, unless you mix in gravity tidal forces etc, which then becomes about GR, not SR.

What that means is that if you according to the far away observer was seen 'moving uniformly' at some speed, relative that observer, it still wouldn't red respectively blue shift any light due to a speed, locally. And you can use Earth to prove that relative speeds (uniform motions) don't blue respectively red shifts the suns light, or any light you use inside your room. In this case we then define the solarsystem as being in a approximately same frame of reference relative each other.

But I have to admit that I don't find it perfect, especially if you rotate that lightclock.

[Yahya (OP)]

I just want to ask a simple question:
if there is time dilation traveling in space with 0.6c m/s and I have a digital watch , what will happen exactly (to my watch) that will make it delay when compared to an on-earth watch? does that mean it ticks slower? if they both reads 4 pm on earth and they differs when I return , what happened exactly ? what is the actual physical process ? I see time as something that is controlled  and not something can control the "watch" and make it move slower. if the watch moves slower does that mean other things on the spaceship move slower as well? then it is a matter of speed and not time.

[yor_on]

That one hinges on how you define time. Your local time, as that wrist watch you use, won't change. You don't 'slow down' locally defined. Time is in a way resembling those uniform motions. Someone else might find you aging slower (or faster depending) relative their clock, but that is in a comparison. Relative your life span time never change.
=

The twin experiment is a setup to define whether time dilation's are 'for real' or just a illusion. And they are real, but you need that twin experiment to prove it. And locally defined time never change as long as we can define you to represent a same frame of reference. That's also why the wrist watch is a popular definition for it.
=

Let me put it this way. People may not realize it but we all, well most of us, instinctively feel that the universe is 'one thing'. That's why we needed that twin experiment, and also why some of us can't accept it. We have a presumption coming from what we experience and in that presumption clocks either tick the same, or they don't. And so we miss that what we go out from is this instinctive response to reality, So the idea of a 'absolute time' builds on a presumption of what a universe is. Einstein really introduced a paradigm change, and even himself couldn't accept some conclusions from it, as 'spooky action at a distance/entanglements'. He too shared this instinctive response of a unified universe, even though he defined time as an 'illusion'. Myself I don't see it that way. To me ones life span is the same and ones wrist watch never lies. The real enigma, to me, is how to join it all into one 'universe'.

That is to say, from my point of view local time is a 'absolute time'. It's your 'proper time' and the one you use from birth to death.

One more thing. Local time is what builds a repeatable experiment. And a repeatable experiment is what physics rests on, and the real test is if it works. It does, otherwise I wouldn't be able to write this.

[Yahya (OP)]

you did not answer my question :
I have a watch classical or digital, the tick of the classical moves by speed one revolution per minute , what would make it reads with delay if its speed did not change? for the digital one the same question.

[yor_on]

I did answer it, it's about presumptions.

[hamdani yusuf]

as a pure byside Yusuf (presuming this your forename, correct me if I'm wrong:) synchronizing 'clocks' is a possibility, but it won't tell us a 'universal time'. Just that those two clocks share a same 'frame of reference' at some original point of place. To define clocks at for example different elevation as 'synchronized' is a no no the way I think about it. Even though one could set them to a same time, they would start to deviate after a while. And so it is with relative speeds too. No way to find a absolute time for anything, just correlations in time and space.

You can call me Dani. Just Dani Okay?
I meant six clocks in the same frame of reference, i.e. clock on earth, clock at 1, 2, 3, 4, and 5 light seconds away from earth. They are stationary relative to each other, so after synchronized, they should tick at the same rate.
- When the rocket twin start moving, his clock should show the same value as the earth clock, which is 0 second.
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 5 light second location?
The rocket then turn around. Is there something interesting happens to his clock?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is coming back to earth?

I'll try to answer those question based on explanation in the video.

According to earth's (and stationary clocks) reference frame:
when the journey start, clock on earth as well as in the rocket show 0 sec.
when the rocket is passing the first clock, it shows 1 sec, while rocket clock shows 0.8 sec.
when the rocket is passing the 2nd clock, it shows 2 sec, while rocket clock shows 1.6 sec.
when the rocket is passing the 3rd clock, it shows 3 sec, while rocket clock shows 2.4 sec.
when the rocket is passing the 4th clock, it shows 4 sec, while rocket clock shows 3.2 sec.
when the rocket is passing the 5th clock, it shows 5 sec, while rocket clock shows 4 sec.
when the rocket is passing the 4th clock, it shows 6 sec, while rocket clock shows 4.8 sec.
when the rocket is passing the 3rd clock, it shows 7 sec, while rocket clock shows 5.6 sec.
when the rocket is passing the 2nd clock, it shows 8 sec, while rocket clock shows 6.4 sec.
when the rocket is passing the first clock, it shows 9 sec, while rocket clock shows 7.2 sec.
when the rocket arrives on earth, earth clock shows 10 sec, while rocket clock shows 8 sec.

According to rocket's reference frame:
when the journey start, clock on earth as well as in the rocket show 0 sec.
when the rocket is passing the first clock, it shows 0.64 sec, while rocket clock shows 0.8 sec.
when the rocket is passing the 2nd clock, it shows 1.28 sec, while rocket clock shows 1.6 sec.
when the rocket is passing the 3rd clock, it shows 1.92 sec, while rocket clock shows 2.4 sec.
when the rocket is passing the 4th clock, it shows 2.56 sec, while rocket clock shows 3.2 sec.
when the rocket is passing the 5th clock, it shows 3.2 sec, while rocket clock shows 4 sec.
when the rocket is turning around 5th clock, it shows a jump to 6.8 sec, while rocket clock still shows 4 sec.
when the rocket is passing the 4th clock, it shows 7.44 sec, while rocket clock shows 4.8 sec.
when the rocket is passing the 3rd clock, it shows 8.08 sec, while rocket clock shows 5.6 sec.
when the rocket is passing the 2nd clock, it shows 8.72 sec, while rocket clock shows 6.4 sec.
when the rocket is passing the first clock, it shows 9.36 sec, while rocket clock shows 7.2 sec.
when the rocket arrives on earth, earth clock shows 10 sec, while rocket clock shows 8 sec.

Hence at the end of the journey both twins agree that earth twin is older then rocket twin.
Is my understanding above correct?

[hamdani yusuf]

What if right after the rocket twin get back to earth, he repeat his journey?
I'll try to analyze it below.

According to earth's (and stationary clocks) reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 11 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 12 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 13 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 14 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 15 sec, while rocket clock shows 12 sec.
when the rocket is passing the 4th clock, it shows 16 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 17 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.

According to rocket's reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 10.64 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 11.28 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 11.92 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 12.56 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 13.2 sec, while rocket clock shows 12 sec.
when the rocket is turning around 5th clock, it shows a jump to 16.8 sec, while rocket clock still shows 12 sec.
when the rocket is passing the 4th clock, it shows 17.44 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 18.08 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18.72 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19.36 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.

[hamdani yusuf]

At a glance, the analysis above looks fine, with rocket twin aging rate is 80% of earth twin.
That's until we realize that to restart the journey, the rocket has to perform acceleration, which in turn should produce time jump.
In the other hand, if the second journey is done in the opposite direction, there would be no acceleration at restarting moment, hence no time jump.

[hamdani yusuf]

as a pure byside Yusuf (presuming this your forename, correct me if I'm wrong:) synchronizing 'clocks' is a possibility, but it won't tell us a 'universal time'. Just that those two clocks share a same 'frame of reference' at some original point of place. To define clocks at for example different elevation as 'synchronized' is a no no the way I think about it. Even though one could set them to a same time, they would start to deviate after a while. And so it is with relative speeds too. No way to find a absolute time for anything, just correlations in time and space.

You can call me Dani. Just Dani Okay?
I meant six clocks in the same frame of reference, i.e. clock on earth, clock at 1, 2, 3, 4, and 5 light seconds away from earth. They are stationary relative to each other, so after synchronized, they should tick at the same rate.
- When the rocket twin start moving, his clock should show the same value as the earth clock, which is 0 second.
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 5 light second location?
The rocket then turn around. Is there something interesting happens to his clock?
- What would his clock show when he is passing the clock at 4 light second location?
- What would his clock show when he is passing the clock at 3 light second location?
- What would his clock show when he is passing the clock at 2 light second location?
- What would his clock show when he is passing the clock at 1 light second location?
- What would his clock show when he is coming back to earth?

I need to make a correction to the scenario above. In order to make the rocket twin ages at 80% rate, he has to go at 0.6c, hence the time dilation factor would be 0.8.
So to make the rocket pass the first clock at 1 second, the distance between adjacent clocks should only be 0.6 light seconds. But the argument is still intact.

[Janus]

What if right after the rocket twin get back to earth, he repeat his journey?
I'll try to analyze it below.

According to earth's (and stationary clocks) reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.
when the rocket is passing the first clock, it shows 11 sec, while rocket clock shows 8.8 sec.
when the rocket is passing the 2nd clock, it shows 12 sec, while rocket clock shows 9.6 sec.
when the rocket is passing the 3rd clock, it shows 13 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 14 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 15 sec, while rocket clock shows 12 sec.
when the rocket is passing the 4th clock, it shows 16 sec, while rocket clock shows 12.8 sec.
when the rocket is passing the 3rd clock, it shows 17 sec, while rocket clock shows 13.6 sec.
when the rocket is passing the 2nd clock, it shows 18 sec, while rocket clock shows 14.4 sec.
when the rocket is passing the first clock, it shows 19 sec, while rocket clock shows 15.2 sec.
when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.

According to rocket's reference frame:
when the journey restart, clock on earth shows 10 sec, while rocket clock shows 8 sec.

Okay

when the rocket is passing the first clock, it shows 10.64 sec, while rocket clock shows 8.8 sec.

No.  it will show  11 sec (just like it does in the Earth frame) .  When the rocket leaves Earth at 0.6c this clock, in the rocket frame already reads 10.36 sec (relativity of simultaneity). It will then advance 0.64 sec between in the time it take for it and the rocket to become adjacent.

when the rocket is passing the 2nd clock, it shows 11.28 sec, while rocket clock shows 9.6 sec.

Again no. This clock will read 12 sec when the rocket passes it, it read 10.72 sec when the rocket left Earth.

when the rocket is passing the 3rd clock, it shows 11.92 sec, while rocket clock shows 10.4 sec.
when the rocket is passing the 4th clock, it shows 12.56 sec, while rocket clock shows 11.2 sec.
when the rocket is passing the 5th clock, it shows 13.2 sec, while rocket clock shows 12 sec.

each of these clocks, like the other two will read the same as what the Earth frame reads. According to the rocket each clock, from 1 to 5 were offset in their readings by 0.36 sec from each other with clock 5 the most advanced.

when the rocket is turning around 5th clock, it shows a jump to 16.8 sec, while rocket clock still shows 12 sec.

As long as the rocket performs this turn around while in the immediate vicinity of Clock 5, it will measure no change in clock 5 and this clock will continue to read 15 min. The other clocks will advance with the furthest one doing so the most.  Clock 4 will jump to 15.36 sec, clock 3 will advance to 15.72 sec, clock 2 will advance to 16.08 sec, clock 1 will advance to 16.44 sec. and the Earth clock will advance to 16.8 sec.
 

when the rocket is passing the 4th clock, it shows 17.44 sec, while rocket clock shows 12.8 sec.

4th clock  16 sec, rocket 12.8 sec

when the rocket is passing the 3rd clock, it shows 18.08 sec, while rocket clock shows 13.6 sec.

3rd clock 17 sec rocket 13.6 sec

when the rocket is passing the 2nd clock, it shows 18.72 sec, while rocket clock shows 14.4 sec.

2nd clock 18 sec rocket 14.4 sec

when the rocket is passing the first clock, it shows 19.36 sec, while rocket clock shows 15.2 sec.

1st clock 179 sec rocket 15.2 sec

when the rocket arrives on earth, earth clock shows 20 sec, while rocket clock shows 16 sec.

Correct.
You will never have a situation where the rocket and any clock that it is passing will disagree as to what their respective clocks read as they passed each other.