Sorry for my ignorance... still trying to get to grips... If a lady in the middle of a moving train sends out beams to the front and back of the train. They reflect off mirrors back to her and arrive simultaneously because she can't do an experiment to give away that she is moving forward rather than being stationary relative to a platform. A man on the platform (that discussed with the lady prior to the journey when to set off a bomb) will see the light hit the back mirror first then the front mirror as the light travelling at c has to catch up with the speeding train's front mirror. He will also see that the beams do not arrive back at the lady at the same time. So to her they arrive together and to him the don't. Now according to the lady she should and does set the bomb off, according to the man they don't arrive in synchs so she doesn't set the bomb off? So this dichotomy confuses me. Would appreciate any help. Glenn.