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great circleThe circular intersection on the surface of a sphere of any plane passing through the center of the sphere. A sphere and its great circles are thus concentric and of equal radius. Compare small circle.
Great Circle(religion, spiritualism, and occult)
A great circle is any circle drawn on a sphere, the plane of which also passes through the inside of the sphere. Great circles are the basis of various systems for locating terrestrial and celestial bodies in terms of sets of coordinates expressed in degrees of a circle. Longitude and latitude are the most familiar of these coordinates. Astrology utilizes several systems of celestial coordinates. Parallel to the manner in which terrestrial coordinates are great circles drawn on the surface of Earth, celestial coordinates are great circles drawn on the inside of the celestial sphere. The ecliptic, the celestial equator, and the prime vertical are examples of some of the great circles used in astrology.