Please be aware that before replying to this message that I will be transferring your replies into another forum (of sorts) Suppose Tom and Jerry get together. They decide that they will devise a simple time measuring device. Each has a tennis ball and both Tom and Jerry (no pun intended) decide that a second will be defined as throwing the tennis ball 5 feet into the air and then the tennis ball will fall back down 5 feet. Therefore ---- 1 second = 10 feet of vertical movement (we won’t consider velocity of the tennis balls as a factor for simplistic reasons). As both stand there with no relative motion between them they agree that a second = 10 feet of vertical motion. Now Jerry gets into the back of a pickup truck going past Tom at ten feet per (tennis ball) second. All that Jerry sees is vertical movement when looking at his ball and so does Tom, when looking at his own ball. When Tom looks at Jerry’s ball going by at ten feet per second he sees both vertical and horizontal movement. Jerry’s clock as compared to Tom’s shows that Jerry’s tennis ball has traveled 20 feet. 10 feet vertically and ten feet horizontally. Jerry’s clock relative to Tom’s ticks slower. (at this point shouldn’t the above scenario be viva versa?) As I was trying to figure out how to explain this I found a problem with time distortion that I once stumbled across. It would seem to me that Jerry would see Tom’s clock slowing down and Tom would see Jerry’s clock is slowing down. So the time distortion would cancel each other out and both Jerry and Tom would march on into the future at the same rate but I know this isn’t the case so we will ask the BBS. Physics BBS: I know time distortion doesn’t cancel each other but I ran into the above problem can anyone set me straight?