[paul cotter]

Halc kindly did the calculation for you and the method he used gives any answer you could possibly need. Acceleration does not occur in the equation he used and is irrelevant.

[Halc]

Nothing you do at a given moment in time can effect what your own clock says at that moment in time.

Can it change what a relatively moving observer see on our accelerating clock?

No. Change requires time, not acceleration.

All that matters is that you pick a frame and figure out the speed of each clock in that frame, and for how long it travels at that speed.  The one formula that is needed (quoted several times above) takes speed as an input, and makes no reference to acceleration.

Change of reference frame requires acceleration.

I said no such thing. If you're going to ignore my posts, then fine. The effort seems unproductive.
A reference frame is a mental abstraction, the assignment of coordinates to events, nothing more. I can change that abstraction any time I want without acceleration. For instance, when driving in my car, I tend to use the rotating frame of the road under me when considering navigation, speed limits, and such. But when I reach for my coffee in the cup holder, I immediately change reference frames to that of the car since that is the most pragmatic frame for the task. That change of reference frame required no acceleration at all.

It's the cause of asymmetric time dilation in twins paradox.

Time dilation is perfectly symmetric in flat spacetime, so that cannot be 'the cause'.  The simplest 'cause' of dilation in flat spacetime is speed relative to a specific inertial frame. That's it. The formula I gave makes no mention of acceleration, so it can be entirely dismissed. Doing it via acceleration works, but is vastly more complicated.

Without it, no twin can conclude that the other twin is older than himself.

This is also incorrect since the conclusion is abstract (mental, not physical) unless they are in each other's presence, in which case it is called 'differential aging', which is the unequal comparison of clocks physically in each other's presence.

The acceleration is irrelevant other than providing the SPEED at which relativistic effects occur.

Exactly.

This topic seems unproductive since the OP refuses to actually accept any of the answers. I might still answer some if they show otherwise.

[hamdani yusuf (OP)]

Halc kindly did the calculation for you and the method he used gives any answer you could possibly need. Acceleration does not occur in the equation he used and is irrelevant.

We can easily remove any parameter from equations. The problem is do they still give the correct answer?

[hamdani yusuf (OP)]

This is also incorrect since the conclusion is abstract (mental, not physical) unless they are in each other's presence, in which case it is called 'differential aging', which is the unequal comparison of clocks physically in each other's presence.

Do you mean that A's clock will be equal to B's clock at the destination point?

[paul cotter]

Yes, one can remove any parameter from any equation. However, the equation then loses it's integrity and any answers obtained will be utterly meaningless.

[hamdani yusuf (OP)]

Yes, one can remove any parameter from any equation. However, the equation then loses it's integrity and any answers obtained will be utterly meaningless.

Without acceleration, A and B's observations should be symmetrical.

[paul cotter]

In your initial query you specified a speed of 40% the speed of light. Obviously acceleration is needed to achieve these speeds but acceleration does NOT figure in the subsequent calculation. This has been explained to you several times and at this point I give up-i'm out.

[hamdani yusuf (OP)]

In your initial query you specified a speed of 40% the speed of light. Obviously acceleration is needed to achieve these speeds but acceleration does NOT figure in the subsequent calculation. This has been explained to you several times and at this point I give up-i'm out.

The problem in discussion on special theory of relativity is many people thinking different things as if they are the same.
Here is the problem statement.

This is a slightly modified twin paradox to distinguish the effects of relative speeds and acceleration.
Twin A started a journey to Alpha Centauri 4 light years away in a space ship moving at 0.4c. He is expected to arrive 10 years later, according to earth observer.
Twin B stayed home to improve the space ship, so he can go to Alpha Centauri 5 years later at 0.8 c.
Classical physics calculation predicts that they'll arrive at Alpha Centauri simultaneously. Does special theory of relativity predict the same?
How old are they when they meet up at Alpha Centauri?

There are three observers here: earth observer, twin A, and twin B. The only observer stays in his frame of reference is the earth. A and B accelerate once. They are seperated for a while, but eventually reunite.
Most people have no difficulty in using earth earth reference frame to calculate relativistic effects. But they start to disagree when they are asked to make the calculation from the travelling twin's frame of reference.

[hamdani yusuf (OP)]

For sanity check, we can add other twins C and D with similar journey to twin B. They make journey from earth to Alpha Centauri at 0.8c. Only starting time is different. C started the journey at the same time as A, and then wait on Alpha Centauri until meeting time with A. D starts the journey 2.5 years after A and C left, and then wait on Alpha Centauri until meeting time. B, C, and D should have the same age when A arrives at the destination point.
A should also get the same results when they are calculated in his frame of reference.

[Origin]

Most people have no difficulty in using earth earth reference frame to calculate relativistic effects. But they start to disagree when they are asked to make the calculation from the travelling twin's frame of reference.

People who have even a basic understanding of relativity don't disagree.

For sanity check,

Why do you need a sanity check?

[hamdani yusuf (OP)]

People who have even a basic understanding of relativity don't disagree.

Are you sure? Do you know that Einstein himself changed his mind several times on this issue?

[hamdani yusuf (OP)]

Why do you need a sanity check?

To make sure the consistency of our arguments and assumptions.
According to A, twin B and C only change their frame of reference once. While D has to change twice. Yet, symmetry requires that all of them have the same age.

[Origin]

Are you sure?

Yes. 
You received the correct answer to your question, so I don't really understand where your confusion is coming from.

[Origin]

According to A, twin B and C only change their frame of reference once.

I don't understand your confusion, especially since it is your scenario.
You should stop referring to inertial frames as frames of reference, using the wrong terminology can lead to additional confusion.
In your scenario twin A starts in the earths inertial frame and then accelerates to a new inertial frame.  He then decelerates to Alpha Centauri's inertial frame, so in your example there are 2 inertial frame changes.  Twin B does exactly the same number of inertial frame changes.  Observer A, B and C all agree on the number of changes in inertial frames of A and B.
I am not going to address observer D since this was not part of the original scenario, it is unnecessary and it only is going to cloud the issue.

[hamdani yusuf (OP)]

Are you sure?

Yes. 
You received the correct answer to your question, so I don't really understand where your confusion is coming from.

What makes you think that they are correct?
The confusion comes from asymmetrical results produced by symmetrical situations.

[hamdani yusuf (OP)]

In your scenario twin A starts in the earths inertial frame and then accelerates to a new inertial frame.  He then decelerates to Alpha Centauri's inertial frame, so in your example there are 2 inertial frame changes.  Twin B does exactly the same number of inertial frame changes.  Observer A, B and C all agree on the number of changes in inertial frames of A and B.
I am not going to address observer D since this was not part of the original scenario, it is unnecessary and it only is going to cloud the issue.

So, you are not confused if the problem can be simplified to 0 or 1 inertial frame change, but you start to get confused with 2 or more inertial frame changes. Cmiiw.

[Origin]

What makes you think that they are correct?

Because the answers are derived from the equations of special relativity which have been shown to always agree with observation and experimentation.

The confusion comes from asymmetrical results produced by symmetrical situations.

If this confuses you, I suggest that you research special relativity.  There are several very good online courses that are free.  These are real course from colleges like Stanford and MIT.

So, you are not confused if the problem can be simplified to 0 or 1 inertial frame change, but you start to get confused with 2 or more inertial frame changes.

No, your scenario is a very straight forward relativity problem and not confusing at all.  You are the one that is claiming this is confusing and unclear.  So just let me repeat; the correct answers were given in reply #1 and reply #3. 

Do you agree that these answers are correct or do you see a problem with the answers?

[hamdani yusuf (OP)]

No, your scenario is a very straight forward relativity problem and not confusing at all.  You are the one that is claiming this is confusing and unclear.  So just let me repeat; the correct answers were given in reply #1 and reply #3.

Do you agree that these answers are correct or do you see a problem with the answers?

You don't seem to understand the core problem in twin paradox situations. Time dilation observed by a relatively moving observer is just half of the problem. The other half is asymmetrical results between the twins, which means that one of them will observe time contraction of the other twin, instead of time dilation. It's the cause of this supposed asymmetry which created disagreement among physicists.

[Origin]

You don't seem to understand the core problem in twin paradox situations. Time dilation observed by a relatively moving observer is just half of the problem. The other half is asymmetrical results between the twins, which means that one of them will observe time contraction of the other twin, instead of time dilation. It's the cause of this supposed asymmetry which created disagreement among physicists.

I do understand the core issue that makes it appear to be a paradox.  But it's not actually a paradox and there is no disagreement between physicists.  The asymmetry is due to one twin changing reference frames.  No confusion if you understand this.

[hamdani yusuf (OP)]

The asymmetry is due to one twin changing reference frames.

How much difference is caused by the changing reference frames?
Is it quantifiable?
Is there any other causes?
If there are more than one changes of reference frames, what difference do those extra changes cause?