ive been trying to study the basics of relativity, and one conceptual problem ive been having is that with the twin paradox (that if one twin went on a rocket which travelled at near light speed, upon returning to earth he would be younger than his/her sibling). the thing is, from the rocket's reference frame, wouldnt the earth be moving at near light speed, hence the sibling on earth would be younger? surely also, if one is older than the other, this would tell them which one of them was moving, which is impossible due to the principle of relativity? (p.s. sorry about the length)

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anonymous · Answer

Well that is the reason its called a paradox.. something that cannot be explained using the theory ... HOWEVEr.. some claim its not really true

cause if they were to meet.. then someone has made a RETURN trip.. and when you do RETURN trip.. you are basically accelerating (cause you change direction).. and hence no longer are you in an inertial frame of refrence.. so no longer can you look at the rockets point of view and apply the law.. cause the law holds good for inertial frames only!