Around 130 to 125 BCE, Hipparchus compared his observations with Babylonian records centuries older and noticed the stars had shifted against the equinox: the equinoctial point creeps backward along the ecliptic about one degree per 72 years, a full circuit in roughly 25,772 years. The cause: Earth is not a sphere but a bulged top, torqued by the sun and moon, wobbling like a slowing gyroscope. Side effects: the pole star rotates through officeholders, Thuban in pyramid-building times, Polaris now, Vega in 14,000 years.
Precession is why your sun sign is wrong: the zodiac signs were fixed to the calendar two millennia ago, but the constellations have since drifted about a full sign west. Astrology kept the old addresses. Astronomy moved. The great ages, Taurus, Aries, Pisces, Aquarius, are simply the sign the equinox currently occupies, each lasting about 2,160 years. Ulansey argues this very discovery detonated the Roman mind and midwifed Mithraism: what god was strong enough to move the entire cosmos?
The claim: precession is civilization's mortality meter, a cycle so long that no culture can watch one complete, meaning every calendar, temple alignment, and pole-star faith is a snapshot pretending to be a law, and the ancients who discovered it realized the heavens run on a warranty no empire will outlive. Verdict: the temples document it, Stonehenge's and Giza's alignments drifted out of true. The archive files it as the antidote to every fixed-truth claim: even the sky's address changes. Slow does not mean stable. It means patient.
If the heavens themselves drift, what was ever fixed?