# rotation

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## rotation

1. Spinning motion of a celestial body or a group of gravitationally bound bodies, such as a galaxy, about an axis, as distinct from orbital revolution. Almost all celestial bodies show some degree of rotation. Young stars arrive on the main sequence with a high rotation rate; this results from the conservation of angular momentum during their collapse from a cloud of interstellar gas. As a star ages, structural changes in its interior and interactions with its surroundings produce changes in its speed of rotation. The hottest (O and B) stars have very great rotation rates of about 200–250 km s–1. Sunlike stars spin more slowly as they age, although some are able to retain their rapid rotation. The faster the rate of rotation the broader and shallower the star's spectral lines and the stronger the magnetic field (see corona). See also differential rotation; direct motion; synchronous rotation.
2. One complete turn of a celestial body about its axis. The Earth takes one sidereal day to make one rotation. Ideally the rotation period of other bodies is measured as the time interval between successive passages of a meridian line on the surface across the center of the disk, as seen from Earth. The solid surface may however be unobservable and indirect measurements, as by radar, are then employed. The rotation period of a gaseous body, such as the Sun or the planet Jupiter, varies with latitude, being greatest at the equator (see differential rotation).
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

## rotation

[rō′tā·shən]
(computer science)
An operation performed on data in a register of the central processing unit, in which all the bits in the register are shifted one position to the right or left, and the endmost bit, which is shifted out of the register, is carried around to the position at the opposite end of the register.
(mathematics)
(mechanics)
Also known as rotational motion.
Motion of a rigid body in which either one point is fixed, or all the points on a straight line are fixed.
Angular displacement of a rigid body.
The motion of a particle about a fixed point.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
(1) An optimal ankle rehabilitation robot design must be characterized with aligned rotation center as the ankle joint, appropriate workspace, and actuation torque.
Based on the analysis results of the wheel state, rotation center changing process, and leg state, motion law of wheellegged structure and motor torques can be obtained.
Instantaneous rotation center [O.sub.p]' is the point at which its velocity is zero on the [Y.sub.p] axis.
The width was larger than the thickness in each cross-section, with the maximum difference of at the point 25 mm above the rotation center, which close to the acetabular dome [Figure 2]a.
From both imaging geometries in Figure 1, the slant range rrot from the SAR sensor to the virtual rotation center can be easily obtained as follows:
In case of the perfectly horizontal measuring system, stable axis of rotation and all star images reduced to the common epoch, a track of chosen point will be the circle of the spherical radius dependent on the difference of spherical coordinates of the rotation center (the zenith) and spherical coordinates of the given point on individual images.
The reverse shoulder is a prosthetic device that switches the ball and socket and moves the rotation center of the shoulder inward to allow the deltoid muscle to raise the arm.
First, by rotating the drive unit around its vertical axis, the rotation center of the robot changes accordingly, allowing the robot to turn around any point in the plane.

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