equinoctial precession cycle

geochronology

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July 19, 2026

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The precession of the equinoxes is a slow, westward movement of the equinoxes along the ecliptic. This phenomenon is caused by the gravitational pull of the Sun and Moon on Earth's equatorial bulge, resulting in a cyclic wobble of Earth's axis of rotation. This wobble has a period of approximately 25,772 years.12

This motion causes the celestial poles and the celestial equator to trace circles in the sky over long periods. For instance, the north celestial pole currently points near Polaris but will shift towards Vega in about 12,000 years. The equinoxes themselves drift westward along the ecliptic at an average annual rate of about 50.4 arc seconds. This phenomenon was first systematically observed by the Greek astronomer Hipparchus when comparing his star catalog with earlier Babylonian measures.134

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…of Earth’s orbital geometry: the equinoctial precession cycle (23,000 years) and the axial-tilt cycle (41,000 years). Although the third parameter of Earth’s orbit, eccentricity, varies on a 100,000-year cycle, its magnitude is insufficient to explain the 100,000-year cycles of glacial and interglacial periods of the past 900,000 years. The origin…
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…of Earth’s orbital geometry: the equinoctial precession cycle (23,000 years) and the axial-tilt cycle (41,000 years). Although the third parameter of Earth’s orbit, eccentricity, varies on a 100,000-year cycle, its magnitude is insufficient to explain the 100,000-year cycles of glacial and interglacial periods of the past 900,000 years. The origin…
Read More