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Two-dimensional
rotation Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...
can occur in two possible directions. Clockwise motion (abbreviated CW) proceeds in the same direction as a
clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and the ...
's hands: from the top to the right, then down and then to the left, and back up to the top. The opposite sense of
rotation Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...
or
revolution In political science, a revolution (Latin: ''revolutio'', "a turn around") is a fundamental and relatively sudden change in political power and political organization which occurs when the population revolts against the government, typically due ...
is (in
Commonwealth English The use of the English language in current and former member countries of the Commonwealth of Nations was largely inherited from British colonisation, with some exceptions. English serves as the medium of inter-Commonwealth relations. Many ...
) anticlockwise (ACW) or (in North American English) counterclockwise (CCW).


Terminology

Before clocks were commonplace, the terms "
sunwise In Scottish folklore, sunwise, deosil or sunward (clockwise) was considered the “prosperous course”, turning from east to west in the direction of the sun. The opposite course, anticlockwise, was known as ''widdershins'' ( Lowland Scots), or ' ...
" and "deasil", "deiseil" and even "deocil" from the
Scottish Gaelic Scottish Gaelic ( gd, Gàidhlig ), also known as Scots Gaelic and Gaelic, is a Goidelic language (in the Celtic branch of the Indo-European language family) native to the Gaels of Scotland. As a Goidelic language, Scottish Gaelic, as well as ...
language and from the same root as the Latin "dexter" ("right") were used for clockwise. "
Widdershins Widdershins (sometimes withershins, widershins or widderschynnes) is a term meaning to go counter-clockwise, to go anti-clockwise, or to go lefthandwise, or to walk around an object by always keeping it on the left. Literally, it means to take ...
" or "withershins" (from
Middle Low German Middle Low German or Middle Saxon (autonym: ''Sassisch'', i.e. "Saxon", Standard German, Standard High German: ', Dutch language, Modern Dutch: ') is a developmental stage of Low German. It developed from the Old Saxon language in the Middle ...
"weddersinnes", "opposite course") was used for counterclockwise. The terms clockwise and counterclockwise can only be applied to a rotational motion once a side of the rotational plane is specified, from which the rotation is observed. For example, the daily rotation of the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surface ...
is clockwise when viewed from above the
South Pole The South Pole, also known as the Geographic South Pole, Terrestrial South Pole or 90th Parallel South, is one of the two points where Earth's axis of rotation intersects its surface. It is the southernmost point on Earth and lies antipod ...
, and counterclockwise when viewed from above the
North Pole The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth's axis of rotation meets its surface. It is called the True North Pole to distinguish from the Magn ...
(considering "above a point" to be defined as "farther away from the center of earth and on the same ray"). Clocks traditionally follow this sense of rotation because of the clock's predecessor: the
sundial A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat ...
. Clocks with hands were first built in the Northern Hemisphere (see ''
Clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and the ...
''), and they were made to work like horizontal sundials. In order for such a sundial to work north of the equator during spring and summer, and north of the
Tropic of Cancer The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward ...
the whole year, the noon-mark of the dial must be placed northward of the pole casting the shadow. Then, when the
Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
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). 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. 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 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. Some clocks were constructed to mimic this. The best-known surviving example is the
Münster astronomical clock The Münster astronomical clock is an astronomical clock in Münster Cathedral in Münster, Germany. The clock, built between 1540 and 1542, is one of the most significant monumental clocks in the German-speaking world. It belongs to the so-cal ...
, whose hands move counterclockwise. Occasionally, clocks whose hands revolve counterclockwise are sold as a novelty. One historic
Jewish Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
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 Hebrew (; ; ) is a Northwest Semitic language of the Afroasiatic language family. Historically, it is one of the spoken languages of the Israelites and their longest-surviving descendants, the Jews and Samaritans. It was largely preserved ...
. In 2014 under
Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...
n president
Evo Morales Juan Evo Morales Ayma (; born 26 October 1959) is a Bolivian politician, trade union organizer, and former cocalero activist who served as the 65th president of Bolivia from 2006 to 2019. Widely regarded as the country's first president to co ...
, the clock outside the Legislative Assembly in
Plaza Murillo The Plaza Murillo is the central plaza of the city of La Paz and the open space most connected to the political life of Bolivia. Prominent buildings on the plaza include the Presidential Palace, National Congress of Bolivia, and the Cathedral of L ...
,
La Paz La Paz (), officially known as Nuestra Señora de La Paz (Spanish pronunciation: ), is the seat of government of the Plurinational State of Bolivia. With an estimated 816,044 residents as of 2020, La Paz is the third-most populous city in Bol ...
, was shifted to counterclockwise motion to promote indigenous values.


Usage


Shop-work

Typical nuts,
screw A screw and a bolt (see '' Differentiation between bolt and screw'' below) are similar types of fastener typically made of metal and characterized by a helical ridge, called a ''male thread'' (external thread). Screws and bolts are used to fa ...
s, bolts,
bottle cap A bottle cap or bottle top is a closure for the top opening of a bottle. A cap is sometimes colourfully decorated with the logo of the brand of contents. Plastic caps are used for plastic bottles, while metal with plastic backing is used for gl ...
s, 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 In mathematics and physics, the right-hand rule is a common mnemonic for understanding orientation of axes in three-dimensional space. It is also a convenient method for quickly finding the direction of a cross-product of 2 vectors. Most of t ...
. 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. Almost all threaded objects obey this rule except for a few left-handed exceptions described below. The reason for the clockwise standard for most screws and bolts is that
supination Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...
of the arm, which is used by a right-handed person to tighten a screw clockwise, is generally stronger than
pronation Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relativ ...
used to loosen. Sometimes the opposite (left-handed, counterclockwise, reverse) sense of threading is used for a special reason. A thread might need to be left-handed to prevent operational stresses from loosening it. For example, some older
car A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded as ...
s and trucks had right-handed
lug nut A lug nut or wheel nut is a fastener, specifically a nut, used to secure a wheel on a vehicle. Typically, lug nuts are found on automobiles, trucks (lorries), and other large vehicles using rubber tires. Design A lug nut is a nut fastener ...
s 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. For
bicycle pedal The pedal is the part of a bicycle that the rider pushes with their foot to propel the vehicle. It provides the connection between the cyclist's foot or shoe and the crank allowing the leg to turn the bottom bracket spindle and propel the bicycle ...
s, the one on the left must be reverse-threaded to prevent it unscrewing during use. Similarly, the flyer whorl of a
spinning wheel A spinning wheel is a device for spinning thread or yarn from fibres. It was fundamental to the cotton textile industry prior to the Industrial Revolution. It laid the foundations for later machinery such as the spinning jenny and spinning ...
uses a left-hand thread to keep it from loosening. A
turnbuckle A turnbuckle, stretching screw or bottlescrew is a device for adjusting the tension or length of ropes, cables, tie rods, and other tensioning systems. It normally consists of two threaded eye bolts, one screwed into each end of a small metal ...
has right-handed threads on one end and left-handed threads on the other. Some gas fittings are left-handed to prevent disastrous misconnections: oxygen fittings are right-handed, but
acetylene Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure f ...
,
propane Propane () is a three- carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used a ...
, and other flammable gases are unmistakably distinguished by left-handed fittings.


Mathematics

In
trigonometry Trigonometry () is a branch of mathematics that studies relationships between side lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies. ...
and mathematics in general, plane
angle In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the ''vertex'' of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles a ...
s are conventionally measured counterclockwise, starting with 0° or 0
radian The radian, denoted by the symbol rad, is the unit of angle in the International System of Units (SI) and is the standard unit of angular measure used in many areas of mathematics. The unit was formerly an SI supplementary unit (before that ...
s pointing directly to the right (or east), and 90° pointing straight up (or north). However, in
navigation Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
,
compass A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with ...
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). A circle defined parametrically in a positive Cartesian plane by the equations and is traced counterclockwise as the angle ''t'' increases in value, from the right-most point at . An alternative formulation with sin and cos swapped gives a clockwise trace from the upper-most point.


Games and activities

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). Traditionally (and still continued for the most part) turns pass counterclockwise in many Asian countries. In Western countries, when speaking and discussion activities take part in a circle, turns tend to naturally pass in a clockwise motion even though there is no obligation to do so. Curiously, unlike with games, there is usually no objection when the activity uncharacteristically begins in a counterclockwise motion. Notably, the game of baseball is played counterclockwise.


Alternative, normal right/left rotation

As an alternative to using a clock to describe the rotation of a body, it is possible to use the right/left hand rule to determine the rotation. The thumb shall point in the normal direction of the surface in question and the four remaining fingers in the direction of the rotation of the surface. The resulting direction of the rotation is thereby * Normal right rotation = counterclockwise * Normal left rotation = clockwise


In humans

Most left-handed people prefer to draw circles and circulate in buildings clockwise, while most right-handed people prefer to draw circles and circulate in buildings counterclockwise. While this was theorized to result from dominant brain hemispheres, research shows little correlation and instead attributes it to muscle mechanics.


See also

* Handedness *
Chirality (physics) A chiral phenomenon is one that is not identical to its mirror image (see the article on mathematical chirality). The spin of a particle may be used to define a handedness, or helicity, for that particle, which, in the case of a massless particle ...
,
Chirality (chemistry) In chemistry, a molecule or ion is called chiral () if it cannot be superposed on its mirror image by any combination of rotations, translations, and some conformational changes. This geometric property is called chirality (). The terms are d ...
* Inner/outer orientation *
Optical isomerism In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...
*
Retrograde motion Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object (right figure). It may also describe other motions such as precession or ...
*
Relative direction In geometry, a position or position vector, also known as location vector or radius vector, is a Euclidean vector that represents the position of a point ''P'' in space in relation to an arbitrary reference origin ''O''. Usually denoted x, r, or ...


References

{{reflist, 2 Concepts in physics Orientation (geometry)