How does a gyroscope maintain its axis to true north?

A gyroscope maintains its axis to true north primarily through the principle of angular momentum, which enables it to resist changes in orientation. When a gyroscope spins, it creates stability due to its rotational inertia. This characteristic allows the gyroscope to maintain its axis even when external forces or movements are applied.

By rotating about the Earth’s horizontal axis, the gyroscope aligns itself with the Earth's rotation, which is related to true north. This alignment is critical for navigation and orientation purposes, as the gyroscope can thus provide a reference point for determining direction relative to the Earth's surface.

The other choices focus on different mechanisms that may contribute to orientation but do not adequately explain how a gyroscope, specifically, maintains its axis. Self-calibration, magnetic orientation, and the aid of gravity can be aspects of guidance systems or navigational aids, but they do not capture the fundamental physics of gyroscopic precession and stability that define how a gyroscope aligns with true north.