An explosive produces a rapid expansion of gases in a very short time. It releases the energy that is stored in the original material in various combinations of the forms of heat, light and gases that occupy a much greater volume than its original form did. The expansion of the gases occurs at a very great speed and they displace great volumes of air. There are fine points to the distinctions between simple explosions and detonations that occur at speeds greater than the speed of sound with resulting shock waves and sonic booms. There are three principle types of explosives: mechanical, chemical and nuclear.