Seriously? It's somehow wrong? Even though it uses correct information and a correct process to get to the correct answer it's not correct?Yes, I'm seriously saying that he CANNOT say that if he conforms to the dictates of SR.
I should have said "as long as you are moving inertially there is no experiment that you can do that will show if you are moving or not" - apologies - typing too quickly on a small screen. The twin paradox does not violate this corrected statement. It is simply a demonstration of the fact that if you treat yourself as inertial when you are not, results that only apply for inertial observers do not work.As far as detecting your own motion, the twin paradox itself provides one method for doing that.
SR says that if you are inertial then there is no absolute sense in which you are either moving or not moving. You are free to choose whichever is convenient for your analysis.SR says that "you can never tell who's moving."