the addition of velocities theorem was part of the reason for my confusion. i couldn't understand why simultaneity occurs when the sound signals are used? surely the observer in the reference frame moving at around c wouldn't hear the sound signal emitted from the point behind he/she?
why we do not observe any “lack of simultaneity” when we substitute sound signals for the light flashes in the “thought experiment” with a train moving past a platform (Einstein's lightning strike-train "thought experiment")?
this has troubled me for 5hours now. i don't know whether it is too...