If the ceiling is two meters high, then person B in the train says the beam light traveled 4 meters. Since the train is moving fast relative to person A, he says that the light traveled more than four meters. In classical theory, this could be explained by saying that the light travels faster because it is in a moving train. According to Micheleson and Moorly's experiment, this could not happen because the speed of light is the same to any moving object traveling at any speed in any direction. So, according to the fundamental formula , the observer concludes that since didn't change and got larger because the light went a longer distance, then should also get larger, and so time on the train goes slower (Haliday 1111). .
Another experiment that can be done to disprove the classical theory is about the addition of speed. In classical theory, if a train is traveling half the speed of light relative to a lamp in a train station, and a person on top of the train is running at half the speed of light relative to the train, then the person on top of the train would catch up to the light coming from the train station. According to Micheleson and Moorly's experiment, this is impossible. This can be explained if the person on the train becomes shorter relative to everything else, or everything else becomes longer relative to the person.
If an object is accelerating away from a light source, according to classical theory, it would eventually catch up to the light, no matter how small the acceleration is. But according to Micheleson and Moorly's experiment, this is impossible. Therefore, scientists hypothesized that the faster an object moves, the more mass it has, and the mass goes to infinity as the speed goes to the speed of light, thus it never can accelerate to the speed of light.
Now consider a big disc rotating in a room. Person A is placed on this disk without knowing that the disc is rotating.
