Puh.
The aging process occur during the whole flight
It doesn't, as my example proved. Anyway, if you don't believe me, believe Wikipedia or any text book on that issue.
a) a mission to mars : departure - 1 year flight to go - turning back - 1 year flight back - landing
b) a mission to juppiter : departure - 4 year flight to go - turning back - 4 year flight back - landing
Following your reasoning the time shift ahould be the same but in case b) it is higher than in a)
no, I didn't say that. The inertial systems that B changes are not the same in scenario a) and b).
Once the twin is back, his clock remains desyncronized
Ok, one last question on this, maybe then you'll see that you are wrong on that.Following your reasoning, which is - again to make sure we're talking about the same thing - turning around has nothing to do with it but ONLY the free (no acceleration/turning/whatever) motion of B in space. How do you explain that B is the older one in the end if NOTHING distinguishes their relative motion?
Therefore there is no reason to emphasize the concept of "inertial " system
It is, because without it the twin paradox is a paradox.
Ok but such kind of abstractions are normal in pyisics !
You can figure out a realistic scenario whereas the effect of turning acceleration / deceleration are negligible
Tell us that scenario, I am quite sure that in this case you can't.
The velocity is , in the equation, in term of : V^2 thus the sign does not play any role
What does the sign of v have to do with that?
The " essence" of the twins paradox lies in the special relativity
Maybe you can do such a calculation for us. The steps B moves away from earth, B turns around and B moves towards earth should be done separately. You may neglect the middle step if you think it is not important.