Mean Motion

Definition

Mean motion is the average angular distance a planet or other celestial body travels during a specified period, commonly expressed in degrees per day. It represents a mathematically smoothed rate rather than the body’s changing apparent speed at a particular moment. Traditional astronomical and astrological calculations distinguish mean motion or mean position from true motion or true position, which accounts more closely for orbital irregularities and the observer’s perspective.

Astrological Meaning

Mean motion is primarily a technical calculation rather than an independent symbol in chart interpretation. Astrologers use it to estimate planetary positions, understand the timing of cycles, and compare a planet’s current apparent speed with its usual rate. It also appears in some traditional forecasting methods and in calculations involving progressions, directions, and planetary periods. The exact application depends on the astrological system being used.

Why It Matters

Understanding mean motion helps explain why planets do not appear to move through the zodiac at a constant rate. A planet may travel faster or slower than its average, become stationary, or appear retrograde. These variations can add context to timing and interpretation, although their significance should be judged alongside sign, house, aspects, and the overall chart. Mean motion also provides essential background for reading ephemerides and evaluating how astrologers calculate positions and developmental techniques.

Related Encyclopedia Entries

• Traditional Astrology
• Astrological Terminology
• Natal Chart