Technically, a gyroscope is any body that spins on a movable axis, including a child's toy top and the Earth itself. A gyroscope maintains a fixed axis of spin in spite of forces of gravity and magnetic fields, making it useful for navigation. Today's ships and aircraft use weighted spinning wheels to stabilize and guide their vessels. In the 1700s the British ships experimented with a spinning rotor to indicate a stable horizontal reference at sea. To avoid being jostled by rolling waters, the rotor had a pivoted support. During the 1800s, two scientists independently demonstrated the rotation of the Earth using the gyroscope's stability in space. One Scottish scientist, named Sang, was unable to construct an accurate spinning wheel, or rotor. Leon Foucault of France, however, succeeded, and in 1852, demonstrated that the axis of a spinning rotor, with its center in a fixed position but able to...