![]() Traditionally (and still continued for the most part) turns pass counterclockwise in many Asian countries. In general, most card games, board games, parlor games, and multiple team sports play in a clockwise turn rotation in Western Countries and Latin America with a notable resistance to playing in the opposite direction (counterclockwise). An alternative formulation with sin and cos swapped gives a clockwise trace from the upper-most point. However, in navigation, compass headings increase clockwise around the compass face, starting with 0° at the top of the compass (the northerly direction), with 90° to the right (east).Ī circle defined parametrically in a positive Cartesian plane by the equations x = cos t and y = sin t is traced counterclockwise as the angle t increases in value, from the right-most point at t = 0. ![]() In trigonometry and mathematics in general, plane angles are conventionally measured counterclockwise, starting with 0° or 0 radians pointing directly to the right (or east), and 90° pointing straight up (or north). Some gas fittings are left-handed to prevent disastrous misconnections: oxygen fittings are right-handed, but acetylene, propane, and other flammable gases are unmistakably distinguished by left-handed fittings. ![]() A turnbuckle has right-handed threads on one end and left-handed threads on the other. Similarly, the flyer whorl of a spinning wheel uses a left-hand thread to keep it from loosening. For bicycle pedals, the one on the left must be reverse-threaded to prevent it unscrewing during use. For example, some older cars and trucks had right-handed lug nuts on the right wheels and left-handed lug nuts on the left wheels, so that, as the vehicle moved forward, the lug nuts tended to tighten rather than loosen. A thread might need to be left-handed to prevent operational stresses from loosening it. Sometimes the opposite (left-handed, counterclockwise, reverse) sense of threading is used for a special reason. The reason for the clockwise standard for most screws and bolts is that supination of the arm, which is used by a right-handed person to tighten a screw clockwise, is generally stronger than pronation used to loosen. Almost all threaded objects obey this rule except for a few left-handed exceptions described below. To apply the right-hand rule, place one's loosely clenched right hand above the object with the thumb pointing in the direction one wants the screw, nut, bolt, or cap ultimately to move, and the curl of the fingers, from the palm to the tips, will indicate in which way one needs to turn the screw, nut, bolt or cap to achieve the desired result. Typical nuts, screws, bolts, bottle caps, and jar lids are tightened (moved away from the observer) clockwise and loosened (moved towards the observer) counterclockwise in accordance with the right-hand rule.Ĭonventional direction of the axis of a rotating body In 2014 under Bolivian president Evo Morales, the clock outside the Legislative Assembly in Plaza Murillo, La Paz, was shifted to counterclockwise motion to promote indigenous values. One historic Jewish clock was built that way in the Jewish Town Hall in Prague in the 18th century, using right-to-left reading in the Hebrew language. Occasionally, clocks whose hands revolve counterclockwise are sold as a novelty. The best-known surviving example is the Münster astronomical clock, whose hands move counterclockwise. Some clocks were constructed to mimic this. This effect is caused by the plane of the dial having been rotated through the plane of the motion of the sun and thus the shadow is observed from the other side of the dial's plane and is observed as moving in the opposite direction. ![]() For a vertical sundial (such as those placed on the walls of buildings, the dial being below the post), the movement of the sun is from right to top to left, and, accordingly, the shadow moves from left to down to right, i.e., counterclockwise. This is why hours must be drawn in horizontal sundials in that manner, and why modern clocks have their numbers set in the same way, and their hands moving accordingly. ![]() Then, when the Sun moves in the sky (from east to south to west), the shadow, which is cast on the sundial in the opposite direction, moves with the same sense of rotation (from west to north to east). In order for such a sundial to work north of the equator during spring and summer, and north of the Tropic of Cancer the whole year, the noon-mark of the dial must be placed northward of the pole casting the shadow. Clocks with hands were first built in the Northern Hemisphere (see Clock), and they were made to work like horizontal sundials. The shadow of a horizontal sundial in the Northern Hemisphere rotates clockwiseĬlocks traditionally follow this sense of rotation because of the clock's predecessor: the sundial. ![]()
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