Precession is 25,694.8 years

Definition

Precession is the gradual change in the orientation of Earth’s rotational axis, caused mainly by the gravitational influence of the Sun and Moon on Earth’s equatorial bulge. A complete cycle is sometimes called the Great Year. The figure 25,694.8 years represents one estimate of its length, although precession varies slightly over time and is commonly rounded to about 26,000 years.

Astrological Meaning

In astrology, precession explains why the tropical and sidereal zodiacs no longer align. The tropical zodiac begins at the March equinox and remains tied to the seasons, while sidereal systems reference stellar positions and apply an ayanamsha to account for the accumulated shift. Precession is also used when discussing astrological ages, such as the Ages of Pisces and Aquarius, though their precise boundaries depend on the method chosen.

Why It Matters

Understanding precession clarifies which zodiac framework an astrologer is using and helps prevent confusion between signs and constellations. It is especially relevant to historical charts, fixed-star work, sidereal astrology, and theories of long-term collective cycles. The exact number should not be treated as an unchanging astrological constant, since astronomical estimates and definitions can differ slightly.

Related Encyclopedia Entries

• Traditional Astrology
• Astrological Terminology
• Natal Chart