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How does a spinning gyroscope keep its direction in space?

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gyrocompass The gyrocompass aboard the National Oceanic and Atmospheric Administration's (NOAA) ship *Rainier*. Gyrocompasses are navigational instruments that use a continuously driven gyroscope to accurately seek the direction of true (geographic) north.

A spinning gyroscope maintains its direction in space due to the principle of angular momentum, which is the product of the wheel's spin and its inertia about the spin axis. Because angular momentum is a vector quantity, it possesses both magnitude and direction; when no external torque is applied, the spin axis remains motionless relative to inertial space—a reference frame nonrotating relative to the "fixed stars".12

By maximizing the moment of inertia and spinning the wheel at a high frequency, the gyroscope creates a large magnitude of angular momentum, which requires a significant torque to change its orientation. When a gyroscope is suspended as nearly as possible at its center of mass, gravity does not apply a torque that would cause it to precess, allowing it to point in a constant direction in space. This property enables the device to detect deviations from a desired orientation, making it a fundamental component in inertial guidance systems and navigational instruments.23