Great Year

Ptolemy reported that his teacher Hipparchus, by comparing the position of the vernal equinox against the fixed stars in his time and in earlier observations, discovered that it shifts westward approximately one degree every 72 years.

In the heliocentric model, the precession can be pictured as the axis of the Earth's rotation making a slow revolution around the normal to the plane of the ecliptic.

Plato hypothesized that winding the orbital motions of the Sun, Moon and naked eye planets forward or back in time would arrive at a point where they are in the same positions as they are today.

The alignment of the axis is maintained throughout the year so that the point of sky above the north or south poles remains unchanged throughout the Earth's annual rotation around the Sun.

[4] Plato (c. 360 BC) used the term "perfect year" to describe the return of the celestial bodies (planets) and the diurnal rotation of the fixed stars (circle of the Same) to their original positions; there is no evidence he had any knowledge of axial precession.

Hipparchus (c. 120 BC) is the first Greek credited with discovering axial precession roughly two hundred years after Plato's death (see below).

Cicero (1st century BC) followed Plato in defining the Great Year as a combination of solar, lunar and planetary cycles.

[6][7] Plato's description of the perfect year is found in his dialogue Timaeus: And so people are all but ignorant of the fact that time really is the wanderings of these bodies, bewilderingly numerous as they are and astonishingly variegated.

The tilt of the Earth's polar axis remains constant but describes a circular path in space during a period known as The Great Year.
The path of the North Pole projected on the sky is a circle which takes 25,772 years to complete. The data in red show the polar point in past epochs and the constellation the vernal equinox was in at that time.
The precession of the axis of a spinning body as seen on a small scale in a gyroscope.