Earth’s spin axis is tilted ~23.5°. That tilt itself slowly “wobbles” (precession), sweeping a circle over thousands of years and pointing Earth’s pole toward different zodiac regions. Below is a sped-up model: the Earth (blue sphere) spins, the axis leans, and that lean precesses around a small cone. The red belt is the ecliptic / zodiac band. One full wobble loop here is 20 seconds — representing 25,920 years (the Great Year) in a 360-day calendar system, with 1° of precession every 72 years.