Suppose you are on am infinitely long train traveling on tracks and an atmosphere that has no resistance whatsoever. No this train is traveling at fractionally below the speed of light, and you are on the train traveling fractionally less than the speed of light in the opposite direction that the train is going thus the train experiences time much slower than the outside world, but you traveling in the opposite direction of the train inside the train experience Time the same as the outside world yet much slower than the train. However this creates a paradox you experience time slower than the train but the same as the outside world, but the train experiences time slower than the outside world and slower than you. My question is how do we solve this paradox to make it true?
All frames of reference are equally valid. If you are inside the train, but running backwards as fast as the train is moving forwards so that you are at rest relative to an outside observer, it will not matter whether you are in the train or outside standing beside the outside observer you will both see the train as moving quickly past, with a slower time frame than yours. An observer in the train, at rest relative to the train could consider the train standing still and you (inside or out) and the outside observer moving quickly past with a slower time frame than his. Both frames of reference are equally valid. Special Theory of Relativity accounts for all this.