How is the modern explanation of precession different from Hipparchus’s explanation?

Hipparchus is credited with the discovery of precession, which he identified by observing that the positions of fixed stars had shifted relative to earlier measurements. While his original writings on the subject have not survived, he is understood to have described this phenomenon as a slow eastward motion of the stars around the zodiac.1

The modern explanation differs significantly by identifying the physical cause of this motion. Today, we understand that the stars themselves are not moving; rather, the effect is caused by a cyclic wobbling in the orientation of Earth’s axis of rotation, which occurs over a period of 25,772 years. This wobble is driven by the gravitational force of the Sun and the Moon acting upon Earth’s equatorial bulge. Consequently, the equinoxes appear to drift westward along the ecliptic as the celestial equator shifts with the axis. While Hipparchus correctly identified the observational pattern, the modern model provides the dynamical explanation rooted in celestial mechanics.12