Gyroscope

A device that uses a spinning rotor or another angular-momentum sensor to measure or maintain orientation and angular velocity.

Angular momentum: A conserved physical quantity associated with rotational motion, determined by an object's mass distribution and angular velocity. A spinning rotor's angular momentum gives it resistance to changes in its rotational axis.
Inertial navigation system: A navigation system that estimates position and velocity by integrating measurements of acceleration and rotation. Its gyroscopes track changes in orientation between external position fixes.
Léon Foucault: A French physicist who demonstrated Earth's rotation with the Foucault pendulum and coined the term gyroscope. His 1852 experiments gave the gyroscope its name and demonstrated its use for detecting Earth's rotation.
Accelerometer: A sensor that measures proper acceleration along one or more axes. It measures linear acceleration, whereas a gyroscope measures angular motion.
Precession: The gradual change in the direction of a rotating body's axis under an applied torque. Torque makes a gyroscope's axis turn sideways rather than simply fall in the direction of the force.
Inertial measurement unit: An instrument combining accelerometers and gyroscopes to measure motion and orientation. Gyroscopes supply its angular-rate measurements, which complement linear acceleration.
Johann Bohnenberger: A German physicist who built an early rotating-top instrument, the machine later called Bohnenberger's machine. His early device anticipated the gyroscope before Foucault named and popularized it.
Magnetometer: An instrument that measures the strength or direction of a magnetic field. It can provide a heading reference, unlike a gyroscope's relative rotation measurement.
Coriolis effect: The apparent deflection of moving objects in a rotating reference frame. Vibrating gyroscopes detect rotation through Coriolis forces acting on their moving elements.
Attitude control: The control of a vehicle's orientation, especially in aircraft and spacecraft. Gyroscopes provide the orientation feedback used by attitude-control systems.

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