Dictionary term
Mean Anomaly
Direct answer
Mean Anomaly is a uniformly increasing angular parameter that measures time since periapsis in an ideal Keplerian orbit.
It is the orbit’s linear-in-time phase angle.
It is the orbit’s linear-in-time phase angle.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.Quick reference
- Use when
- Use it with mean motion, epoch, and Kepler’s equation.
- Do not use it for
- It is a computational angle, not usually the body’s visible direction.
- Reference category
- Astronomy & Skywatching
- Related terms
- Argument of Periapsis, True Anomaly, Eccentric Anomaly, Orbital Period
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The story behind Mean Anomaly
Kepler introduced related auxiliary constructions to connect time with elliptical position.
Mean Anomaly: fact and faith, kept distinct
This is a factual astronomy reference. It can support wonder at the created order without becoming a claim of fate, worship, or private revelation.
Mean Anomaly in numerology
Mean Anomaly is not a numerology claim. Any numbers attached to it should retain their ordinary scientific, calendrical, navigational, or historical meaning unless a separate symbolic interpretation is clearly labeled.
Why Mean Anomaly matters
It makes orbital timing easier before solving for the actual geometric position.
Mean Anomaly at work: an example
Mean anomaly advances evenly even while an eccentric planet’s true anomaly does not.
Where interpretation stops
Mean Anomaly is presented as sourced astronomy, calendrical, Earth-science, cultural, or instrument-history reference. Definitions should distinguish measured phenomena from civil convention and historical interpretation, preserve location and time dependencies, and avoid turning factual sky data into a deterministic personal claim.
Sources and editorial method
Research references used for this entry include:
- NASA Science: Orbits and Kepler’s Laws - NASA explanation of orbital ellipses, orbital periods, and Kepler’s laws of planetary motion.
- U.S. Naval Observatory: Astronomical Almanac Glossary - Definitions for astronomical coordinates, time, reference systems, and observable phenomena.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Also appears in
- Astronomy & Skywatching
- Aliases
- None listed
- Last updated
- 2026-07-16
Follow uniform orbital phase
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More in Astronomy & Skywatching
- Perihelion
- Red Supergiant
- Solar Photosphere
- Transit of Venus
- Apparent Field of View
- Bond Albedo
- Elliptical Galaxy
- Hertzsprung-Russell Diagram
Common questions
What is Mean Anomaly?
Mean Anomaly is a uniformly increasing angular parameter that measures time since periapsis in an ideal Keplerian orbit.
How is Mean Anomaly used in an almanac?
Use it with mean motion, epoch, and Kepler’s equation.
What should I avoid when interpreting Mean Anomaly?
It is a computational angle, not usually the body’s visible direction.
