precession

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precession Wobble of the axis of a spinning object. It occurs as a result of the torque on the spin axis, which increases as the angle of precession increases. The Earth precesses about a line through its centre and perpendicular to the plane of the ecliptic extremely slowly (a complete revolution taking 25,800 years) at an angle of 23.5°. The motion of a gyroscope is another consequence of precession, because the entire ring containing the spinning wheel and its axle precesses around the support pivot.

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