this isn't my explanation, but I was just wondering what others thought: "Einstein's special theory of relativity showed that an object can be of two different sizes for two different people and that they can perceive the time between two events to have different duratoins. His General theory of relativity suggested that space itself is not just a stage for the material world to act on, but is an active participant in the play. Space, for example, gets bent out of shape by any matter that is hanging about in it. The relativity theory talks a lot about "frames of reference." From the point of view of relativity, things standing still with respect to one another are in the same frame of reference. Things moving relative to one another have different frames of reference. Distorting a frame of reference is equivalent to distorting space itself, and it is this distortion, by the agency of gravity, that the general theory predicts." I don't know too much about general relativity, but is the part at the beginning, about special relativity true? I thought if two objects were of different velocities (rather than size) that the duration changes?