# great circle

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## great circle

Geometry a circular section of a sphere that has a radius equal to that of the sphere

## great circle

The 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.

## great circle

[′grāt ¦sər·kəl]
(geodesy)
A circle, or near circle, described on the earth's surface by a plane passing through the center of the earth.
(mathematics)
The circle on the two-sphere produced by a plane passing through the center of the sphere.

## great circle

Two great circle in a sphere.
A circle on the surface of the sphere (earth) whose center and radii are those of the sphere itself. Only one great circle may be drawn through two places that are not diametrically opposite on the surface of a sphere. The shortest distance between any two points on the surface is the smaller arc of the great circle joining them. An aircraft following a great circle (other than directly true north or south) will have to alter course constantly. The intersection of a sphere and a plane that does not pass through its center is called a small circle.
References in periodicals archive ?
The shipment of Great Circles Trading came in one 40-foot container declared as "scales toys and other merchandise" but was found to contain used clothing approximately valued at around P7.
In other words, we show that forces cannot keep any such point at rest or make it move uniformly along a great circle of [S.
Any two great circles will intersect in two points that are antipodes of each other.
We have devised a problem to test students' understanding of great circles and to help them realise that the Earth surface covering a relatively small area can be estimated by plane geometry whereas that covering a relatively large area cannot.
A "straight line" in an elliptic plane is an arc of great circle on the sphere.
The correct determination, for example, of the circumferences of great circles at aphelion and perihelion seem to be beyond practical determination.
I comment on several of these propositions below, noting how they come out true if the terms 'right line' and 'straight line' (which Reid uses interchangeably) are taken to denote great circles of the sphere (or segments of such circles).
The years provided further glimpses: Sanders at the twenty-fifth anniversary of On the Road's publication in Boulder, a ten-day celebration where not only attendees imbibed ritualistically but Trungpa Rinpoche swigged sake from the stage as he addressed the enclave, moving his arms in great circles symbolizing OM, universal peace.
The meridians of longitude loop from the North Pole to the South and back again in great circles of the same size, so they all converge at the ends of the Earth.
After consideration of various arrangements of framing, a treble intersection system of ribs, all of which lay on great circles of the dome for the whole or part of their length, were adopted'.
Indeed, it resembles the geometry on the surface of a sphere, where all great circles (those that divide the surface into equal halves) are finite in length and intersect.
Scanning the heavens in great circles that pass through the north and south ecliptic poles, the German-built X-ray telescope imaged much fainter objects and achieved an angular resolution three times greater than the orbiting Einstein Observatory, which conducted a smaller X-ray imaging survey in 1979.

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