Yea because i experienced the same as you , great logic <| sep |> I ' m still struggling to understand so bear with me . I ' m imagining a very long stretch of ship moving at c lets say a runway of sort and on top of that runway I , along the top of the ship moving at c , speed up to c or something close to it . As you said relativistic velocity isn ' t the same , but to anyone not on this ship they ' d see someone moving twice as fast or in general moving faster than the ship because their traversing it . From what you say , or at least what I gather , what I am proposing isn ' t possible in either relativistic velocity or classical because nothing can go faster than the speed of light . Then what would happen if someone or something did this experiment . On a ship moving 0 . 9 c a person moving on top the ship at 0 . 9 c then from off the ship the person would be moving at 1 . 8 c , if you say that is not possible what would stop the person from moving about . 9999999 c very close to c you get the point .