[hamdani yusuf (OP)]

It's seems to me that you are trying as hard as possible to Not understand Relativity.

It seems like that to you because you've been misunderstanding it without you realized.

What's the reading of the travelling clock by midway observer, one day before passing the mid point, and one day after passing it?

[Janus]

It's seems to me that you are trying as hard as possible to Not understand Relativity.

It seems like that to you because you've been misunderstanding it without you realized.

What's the reading of the travelling clock by midway observer, one day before passing the mid point, and one day after passing it?

Outbound trip:
0ne day prior to ship arriving( by Midpoint's clock):

Actual time on ship clock: 32 days, 15 hrs, 34 min and 13.5718217858 sec.

What the Midpoint observer visually sees: The ship sitting at its planet of origin, waiting to depart.

One day after ship passes midpoint:

Actual time on ship:  32 days, 17 hrs, 42 min, and 59.490547741 sec

What the observer visually sees: 32 days, 17 hrs, 10 min, 48.9770892 sec

During return leg:


One day before: 
Actual time: 98 days 0 hr, 51 min, 26.63419131 sec

What is visually seen: The ship not quite having reached the turn around point, and a bit short of reading 65 days 9hr, 17 min, and 13.06236952 sec
One day after:
Actual time: 98 days 3 hrs, 0 min, 12.55291726 sec

What is visually seen: 98 days 2 hr, 28 min, and 12.5529176 sec.

[paul cotter]

Hamdani, here is an analogy: suppose we have a coil and we want to produce a magnetic field with it, then what is required? We need to put a certain level of current through it, how do we do that? We apply a voltage. Now which produces the magnetic field, the voltage or the current? We know the current was responsible but we needed a voltage to do that. Similarly the acceleration is needed to produce the speed necessary for the relativistic effects but the speed is what determines the outcome, not the acceleration.

[hamdani yusuf (OP)]

It's seems to me that you are trying as hard as possible to Not understand Relativity.

It seems like that to you because you've been misunderstanding it without you realized.

What's the reading of the travelling clock by midway observer, one day before passing the mid point, and one day after passing it?

Outbound trip:
0ne day prior to ship arriving( by Midpoint's clock):

Actual time on ship clock: 32 days, 15 hrs, 34 min and 13.5718217858 sec.

What the Midpoint observer visually sees: The ship sitting at its planet of origin, waiting to depart.

One day after ship passes midpoint:

Actual time on ship:  32 days, 17 hrs, 42 min, and 59.490547741 sec

What the observer visually sees: 32 days, 17 hrs, 10 min, 48.9770892 sec

During return leg:


One day before: 
Actual time: 98 days 0 hr, 51 min, 26.63419131 sec

What is visually seen: The ship not quite having reached the turn around point, and a bit short of reading 65 days 9hr, 17 min, and 13.06236952 sec
One day after:
Actual time: 98 days 3 hrs, 0 min, 12.55291726 sec

What is visually seen: 98 days 2 hr, 28 min, and 12.5529176 sec.

I appreciate your effort to do the calculations. Now we can narrow down the observation around the passing event at mid point.

What's the reading of the travelling clock by midway observer, one second before passing the mid point, and one second after passing it?
At least in principle, we should be able to narrow down further to microsecond or picosecond, to approach the reading exactly at the passing event.

[hamdani yusuf (OP)]

Hamdani, here is an analogy: suppose we have a coil and we want to produce a magnetic field with it, then what is required? We need to put a certain level of current through it, how do we do that? We apply a voltage. Now which produces the magnetic field, the voltage or the current? We know the current was responsible but we needed a voltage to do that. Similarly the acceleration is needed to produce the speed necessary for the relativistic effects but the speed is what determines the outcome, not the acceleration.

We are trying to find the symmetry breaker in the twin paradox case. In the original case, one twin accelerates, while the other doesn't. That difference is thought to be the reason to disqualify the travelling twin from applying simple Lorentz transform and observe time dilation experienced by staying twin. Otherwise, both twins will see the other's clock to be slower than their own, which is a contradiction.
Where's the symmetry breaker in your analogy?

[paul cotter]

Hamdani, i'm a bit late to the party and my comment would have been more appropriate earlier when the significance of acceleration was being discussed.

[Janus]

Hamdani, here is an analogy: suppose we have a coil and we want to produce a magnetic field with it, then what is required? We need to put a certain level of current through it, how do we do that? We apply a voltage. Now which produces the magnetic field, the voltage or the current? We know the current was responsible but we needed a voltage to do that. Similarly the acceleration is needed to produce the speed necessary for the relativistic effects but the speed is what determines the outcome, not the acceleration.

We are trying to find the symmetry breaker in the twin paradox case. In the original case, one twin accelerates, while the other doesn't. That difference is thought to be the reason to disqualify the travelling twin from applying simple Lorentz transform and observe time dilation experienced by staying twin. Otherwise, both twins will see the other's clock to be slower than their own, which is a contradiction.
Where's the symmetry breaker in your analogy?

The difference is in what happens according to the Twin that undergoes the acceleration while under they are under acceleration.

When the two have a constant velocity with respect to each other, they both are able to simply apply the time dilation formula to the other's clock. 
In fact, the non-traveling twin, since he never experiences any acceleration, can always do such.  For Him, the only thing that happens to the other twin during the acceleration is that the time dilation rate changes as the relative velocity changes.

It's different for the Twin actually undergoing the acceleration. On top of the time dilation due to changing velocity, there are other factors affecting his measurements.  Clocks in the direction of the his acceleration will run faster, and one in the opposite direction will run slower, according to him.  This even includes clocks within his own ship that are not moving relative to him by his measure.  A clock in the nose of the ship run faster than one in the middle, which runs faster than one in the tail.*

The difference in tick rate this creates by his determination is proportional not only to the magnitude of the acceleration, but also the distance separating the clocks.  This is what leads to him agreeing at the end of the trip that he has aged less than his stay at home twin, even though fro the majority of the trip he would have said that it was the stay at home twin that was aging slower.  For him, his brother aged slow, then aged really fast, then aged slow again, with it all adding up at the end with his twin having aged more in total.

Again, this is what each twin determines after factoring out light propagation delays.
As to what they actually see:
Stay and home twin:
1. Sees traveler receding and ticking slow by the Doppler shift factor. He will see this for the amount of time needed fro the ship to reach the destination plus the time it take for light to travel from there to him. (with a 4 light year trip and traveling at 0.999 c, it will be 8.004 yrs, ticking at a rate of 0.0224, accumulating ~0.179 yrs. 
Then, for 0.004 yrs ( total trip time minus the above) it sees a Doppler effect rate of 44.71, seeing the ship accumulate another  ~.179 yrs. this gives 0.358 yrs total for the ship and 8.008 for Earth.

For the traveling twin, the 4 ly distance as measured from Earth is only ~.01788 ly due to length contraction by his measure, which takes 0.179 yrs to cross at 0.999 c.   During which time he sees the Earth age ~0.004 yrs due to Doppler shift.  Now, since he is the one doing the acceleration, and thus making the change of velocity, he doesn't have to wait any time to see the effect this has on the Doppler shift, but will see an immediate change to the ~44.71 rate, which he then sees for the ~0.179 yrs needed to return to the Earth, adding 8.004 yrs to the 0.004 yrs for a total of 8.008 yrs for Earth upon return, to his 0.358 yrs.

*Our non- accelerating observer will also note a difference in these clocks, but for a different reason. In his frame, The ship, as a whole, is changing velocity with respect to him, thus its length contraction is also changing.  This, in turn, means that the ends of the ship cannot be traveling at equal velocities relative to him, and the clocks at the ends have different time dilation rates and not tick in sync.

[hamdani yusuf (OP)]

For him, his brother aged slow, then aged really fast, then aged slow again,

Why in return trip the travelling twin observes slow age of staying on earth twin, when they are moving closer?

[hamdani yusuf (OP)]

It's seems to me that you are trying as hard as possible to Not understand Relativity.

It seems like that to you because you've been misunderstanding it without you realized.

What's the reading of the travelling clock by midway observer, one day before passing the mid point, and one day after passing it?

Outbound trip:
0ne day prior to ship arriving( by Midpoint's clock):

Actual time on ship clock: 32 days, 15 hrs, 34 min and 13.5718217858 sec.

What the Midpoint observer visually sees: The ship sitting at its planet of origin, waiting to depart.

One day after ship passes midpoint:

Actual time on ship:  32 days, 17 hrs, 42 min, and 59.490547741 sec

What the observer visually sees: 32 days, 17 hrs, 10 min, 48.9770892 sec

During return leg:


One day before: 
Actual time: 98 days 0 hr, 51 min, 26.63419131 sec

What is visually seen: The ship not quite having reached the turn around point, and a bit short of reading 65 days 9hr, 17 min, and 13.06236952 sec
One day after:
Actual time: 98 days 3 hrs, 0 min, 12.55291726 sec

What is visually seen: 98 days 2 hr, 28 min, and 12.5529176 sec.

I appreciate your effort to do the calculations. Now we can narrow down the observation around the passing event at mid point.

What's the reading of the travelling clock by midway observer, one second before passing the mid point, and one second after passing it?
At least in principle, we should be able to narrow down further to microsecond or picosecond, to approach the reading exactly at the passing event.

You can put your formulas in a spreadsheet, so that you can change the time of interest to any value and immediately get the results.

[hamdani yusuf (OP)]

What will travelling earth twin see about travelling Alpha Centauri twin?
Di they have the same age at meeting point?

[Janus]

What will travelling earth twin see about travelling Alpha Centauri twin?
Di they have the same age at meeting point?

I've already covered this in an earlier post. (while in that example I assume a 0.8 c rather than 0.999 c, the basic math still applies. )

When two or more clocks pass each other, everyone will agree as what they read as they do so.  The fact that the traveling Earth twin, the traveling AC twin and the midpoint clock all agree as to what times each of them read as they pass is mundane and is to be expected( in fact, required for us to live in a consistent universe).    You are really not going to learn anything about Relativity from this.

[hamdani yusuf (OP)]

I've already covered this in an earlier post. (while in that example I assume a 0.8 c rather than 0.999 c, the basic math still applies. )

You haven't mentioned the observation of a travelling twin on the clock of the other travelling twin when they meet at mid point.

[hamdani yusuf (OP)]

When two or more clocks pass each other, everyone will agree as what they read as they do so.  The fact that the traveling Earth twin, the traveling AC twin and the midpoint clock all agree as to what times each of them read as they pass is mundane and is to be expected( in fact, required for us to live in a consistent universe).    You are really not going to learn anything about Relativity from this.

There must be some reasons why after more than a century, there are still disputes even among experts and researchers on the cause of twin paradox. They seem to be convinced by the end results, but they disagree on how they get that same results. That's a problem with thought experiments.

[Janus]

I've already covered this in an earlier post. (while in that example I assume a 0.8 c rather than 0.999 c, the basic math still applies. )

You haven't mentioned the observation of a travelling twin on the clock of the other travelling twin when they meet at mid point.

In reply #88
ES is the Earth traveling twin
ACS is the Alpha Centauri traveling twin
Velocites of ES and ACS to the planets and midpoint: 0.8c (As already mentioned, the exact value really does not matter in the big picture)

Events according to ES, starting from the moment it reaches 0.8c relative to Earth
ACS time = ~1.26 yr
Distance of ACS to midpoint = ~0.283 ly
Relative velocity of ACS to ES = ~0.976c (addition of velocities)
Time dilation factor for ACS according to ES = ~0.22
closing speed between  ACS and midpoint = ~0.176c  (0.976c-0.8c)
Distance to midpoint for ES = ~1.29 ly (length contraction)
Time for ES to reach midpoint = ~1.61 yr
time for ACS to reach midpoint = ~1.61 yr (0.28 ly/.176c)*
Time accumulated for ACS while ES travels to midpoint = ~0.354 yr (1.61*0.22)
Time on ACS upon arrival to midpoint ~1.61 yr (1.26yr+0.354 yr)

[Janus]

When two or more clocks pass each other, everyone will agree as what they read as they do so.  The fact that the traveling Earth twin, the traveling AC twin and the midpoint clock all agree as to what times each of them read as they pass is mundane and is to be expected( in fact, required for us to live in a consistent universe).    You are really not going to learn anything about Relativity from this.

There must be some reasons why after more than a century, there are still disputes even among experts and researchers on the cause of twin paradox. They seem to be convinced by the end results, but they disagree on how they get that same results. That's a problem with thought experiments.

Except there really is no real dispute.   What you see as a disagreement by looking at a couple of YouTube  videos, are merely different approaches at explaining it to a layman audience.  And it really isn't that easy for these experts to do so.
The big problem is that they are so familiar with the subject that they tend to see certain parts of it as obvious and don't go over it as clearly as they should, because they assume the audience will also see it as obvious.  This can leave things open for the audience to misinterpret what is being said.

[hamdani yusuf (OP)]

AC time = 3.44 yr (relativity of simultaneity)

Where do you get this number from?

[Janus]

AC time = 3.44 yr (relativity of simultaneity)

Where do you get this number from?

As stated, it is due to the Relativity of Simultantaneity.  It can be calculated by vx/c^2, where
v is the relative velocity between ES and AC,
x is the Earth AC distance measured in the Earth rest frame.
It gives you the difference between the Earth clock and the AC clock in the rest frame of ES, assuming that they read the same in the Earth/AC rest frame.
Earth clock reads 0 at that moment, So AC clock reads 0.8c x 4.3 ly/ c^2 = 3.44 yrs.
This is also consistent with the fact that it takes 3.225 years by the ES clock to reach AC.  During which time the AC clock is ticking slow by a factor of 0.6 and accumulates 1.935 yrs according to ES. But it reads 5.375 yrs upon the arrival of ES. 5.375-1.935 = 3.44,  So the AC clock had to already read 3.44 yrs as ES left Earth according to ES.
If you want to use a 4 ly distance and a velocity of 0.999c, then  the AC clock reads 3.996 yrs when ES leaves Earth according to ES,

[hamdani yusuf (OP)]

Earth clock reads 0 at that moment, So AC clock reads 0.8c x 4.3 ly/ c^2 = 3.44 yrs.

At that moment, what does the midway clock read?

What does the midway clock read in the case below?

If you want to use a 4 ly distance and a velocity of 0.999c, then  the AC clock reads 3.996 yrs when ES leaves Earth according to ES,

[hamdani yusuf (OP)]

What's the reading of the travelling clock by midway observer, one second before passing the mid point, and one second after passing it?

[alancalverd]

Whose second?