The curious behavior of a gyroscope never ceases to fascinate. It is the quintessential lecture demonstration whenever examples of angular momentum are discussed. The gyrocompass is but one example of its application. With conservation of angular momentum in mind, most students probably imagine a gyrocompass as simply a “directional” gyroscope in the sense that a gyroscope (spinning freely in a gimbal mount) maintains its axis orientation regardless of how it is moved around. They would probably be surprised to learn that if you constrain the rotational axis of a gyroscope to move in a horizontal plane, the axis will align itself with Earth's meridian in a north-south direction—it seeks out and indicates true geographic north and in no way depends upon Earth's magnetic field! A true gyrocompass is designed to sense Earth's rotation and that coerces the gyro to orient its spin axis to be in the plane containing Earth's...

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