It is a little known fact that Alexander the Great invented a primitive form of wristwatch. In order to synchronize his forces during battles, he ordered a special chemical to be developed that changed color with the passage of time. A small piece of cloth was dipped in the solution, and worn around the wrist. In this way, all his troops could know what time it was, enabling them to carry out sophisticated military campaigns and thus conquer the world.Historians refer to this invention as "Alexander's rag time-band."