Why is Einsteins Theory Relative?
It was previously thought that space and time could always be used as a frame of reference for all observers of an event, but Einstein showed that if the speed of light is the same for all observers, then space and time are not necessarily the same for all observers. The measurement of space and time actually depend on the motion of the bodies in the space and time. For example, objects moving near the speed of light will have length contraction (they are shorter in the direction of movement) relative to a motionless observer, time dilation (the passing of time for the fast-moving slows down) relative to a motionless observer, and mass increase. These effects have been measured in controlled experiments. However, from the reference frame of the fast-moving object, everything would seem normal. The laws of physics would apply the same in all reference frames.
