A gyroscope uses the principles of conservation and angular momentum to measure and maintain orientation. The mechanical gyroscope is a spinning wheel or disk whose axle is free to take any orientation. The gyroscope’s high rate of spin allows for large angular momentum which makes the orientation changes much more responsive to a given external torque. There is also the electronic, microchip-packaged MEMS gyroscope, solid state ring laser and fiber optic gyroscope, as well as the extremely sensitive quantum gyroscope.

Gyroscopes are used for navigation when magnetic compasses don’t work, such as in telescopes or ICBM’s. They are also used for stabilization of flying vehicles and used to maintain direction in tunnel mining.

The gyroscope is composed of a rotor journaled to spin about one axis that is mounted in an inner ring which is journaled for oscillation in an outer gimbal which in turn is journaled for oscillation relative to a support. The outer gimbal, with one degree of rotational freedom, is mounted to pivot about an axis, which has no degree of rotational freedom, in its own plane determined by the support.

The behavior of a gyroscope is similar to the front wheel of a bicycle. When the wheel is leaned away from the vertical so that the top of the wheel moves to the left, the forward rim of the wheel also turns to the left. So rotation on one axis of the turning wheel produces rotation of the third axis.

The center of gravity of the rotor can be in a fixed position. The rotor can spins about the one axis and is capable of oscillating about the two other axes. Except for its inherent resistance due to rotor spin, it can turn in any direction about the fixed point. Other designs of gyroscopes can have the mechanical equivalents substituted for one or more of the elements such as the spinning rotor may be suspended in a fluid instead of being pivotally mounted in gimbals.

Sometimes the outer gimbal may be omitted so that the rotor has only two degrees of freedom. Other times the center of gravity of the rotor may be offset from the axis of oscillation, therefore, the center of gravity of the rotor and the center of suspension of the rotor may not coincide.

German Johann Bohnenberger made the first gyroscope-like instrument in 1817. His machine was based on a rotating massive sphere. Walter R. Johnson made a similar device based on a rotating disk in 1832. Pierre-Simon Laplace brought the machine to Leon Foucalt’s attention when he suggested using it as a teaching aid. Foucault was the one who gave the apparatus its modern name.

The first prototype gyroscope was made in the 1860’s when electric motors made the concept feasible. In 1908 the first marine gyrocompass was patent by Hermann Anschutz-Kaempfe. Elmer Sperry later made his own design. At this point other nations took note of the value of the gyroscope in Naval battle. In 1917 the gyroscope was made as a toy and has been a classic in America ever since.

The gyroscope was used as the basis for early black box navigational systems in the first several decades of the 20th century. The gyroscope became the prime component for aircraft during World War II.