Dictionary term
Great Circle
Direct answer
Great Circle: A Great Circle is the intersection of a sphere with a plane passing through the sphere’s center.
It is the largest possible circle on a sphere.
It is the largest possible circle on a sphere.
A scientific orientation to scale, light, or motion; the article supplies the precise definition.Quick reference
- Use when
- Use spherical rather than flat-map geometry for wide sky separations.
- Do not use it for
- A straight line on a chart projection may not represent a great-circle arc.
- Reference category
- Astronomy & Skywatching
- Related terms
- Astronomical Nadir, Prime Vertical, Small Circle, Celestial Horizon
The Chapter · Mystery School
Learn to read the sky for yourself
A mystery school of astrology with a worldwide chapter: letters on the chart and the soul, readings under one sky, and a rule of honesty about what the stars can and cannot say.
- The founding letter, with what the school studies and how it meets
- First word each season, when the doors open
- A seat at the gatherings, wherever in the world you are
Reading about Great Circle? The chapter is where readers like you meet.
Founding circle · forming now
The list costs nothing. Word of the school and its gatherings, nothing else. Unsubscribe at any time.
The story behind Great Circle
Great circles have been foundational in astronomy, geography, and navigation.
Great Circle: 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.
Great Circle in numerology
Great Circle 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 Great Circle matters
Great-circle arcs define angular separation and shortest routes on spherical models.
Great Circle at work: an example
The celestial equator and every hour circle are great circles.
Where interpretation stops
Great Circle 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:
- U.S. Naval Observatory: Astronomical Almanac Glossary - Definitions for astronomical coordinates, time, reference systems, and observable phenomena.
- International Astronomical Union: Standards of Fundamental Astronomy - IAU-maintained standards and algorithms for astronomical reference systems and coordinate transformations.
- Source
- The Great Almanac Dictionary
- Category
- Astronomy & Skywatching
- Also appears in
- Astronomy & Skywatching
- Aliases
- None listed
- Last updated
- 2026-07-16
Measure an arc across the sky
Great Circle in a book is one thing; Great Circle in your own birth chart is your life. The Oracle casts your real chart and tells you what it means for your love, your work, and your year ahead, in conversation, free.
Speak with the OracleRelated terms
More in Astronomy & Skywatching
- Longitude of Ascending Node
- Orbital Resonance
- Radial Velocity
- Solar Chromosphere
- Telescope Aperture
- Annual Aberration
- Aurora
- Diffraction Limit
Common questions
What is Great Circle?
A Great Circle is the intersection of a sphere with a plane passing through the sphere’s center.
How is Great Circle used in an almanac?
Use spherical rather than flat-map geometry for wide sky separations.
What should I avoid when interpreting Great Circle?
A straight line on a chart projection may not represent a great-circle arc.
