I was watching a vid with Mr Hawking talking about a train (fictional) that gets to 99.9 C. and the little girl gets up and runs forward. "as time in the train has slowed down. her momentum is not added to that of the trains speed. So she never reaches C" A. trains %99.9 of C B. time inside the train slows down. C. the girls speed IS added to the trains but because time slowed down Even more? she cant hit C? Tomcat does mach2 fires a sidewinder that does mach2. for a short bit. that winder IS doing mach4. so why is Suzie's speed not added to the trains and thus she is moving faster than the train. PLEASE KEEP THE ANSWER SIMPLE. I'M STUPID.