Great circle
A great circle is a
circle on the surface of a
sphere that has the same circumference as the sphere, and divides the sphere into two equal hemispheres. Equivalently, a great circle on a sphere is a circle on the sphere's surface whose center is the same as the center of the sphere. A great circle is the intersection of a sphere with a plane going through its center. A great circle is the largest circle that can be drawn on a given sphere.
Great circles serve as the analog of "straight lines" in spherical geometry. See also
spherical trigonometry and geodesic.
The great circle on the spherical surface is the path with the smallest
curvature, and hence an arc is the shortest path between two points on the surface.
Encyclopedia
A
great circle is a
circle on the surface of a
sphere that has the same circumference as the sphere, and divides the sphere into two equal hemispheres. Equivalently, a great circle on a sphere is a circle on the sphere's surface whose center is the same as the center of the sphere. A great circle is the intersection of a sphere with a plane going through its center. A great circle is the largest circle that can be drawn on a given sphere.
Great circles serve as the analog of "straight lines" in spherical geometry. See also
spherical trigonometry and geodesic.
The great circle on the spherical surface is the path with the smallest
curvature, and hence an arc is the shortest path between two points on the surface. The distance between any two points on a sphere is known as the
great-circle distance. When intercontinental airline routes are drawn on a flat map , they often look curved. This is because they lie on great circles. A route that would look like a straight line on the map would actually be longer.
On the Earth, the
meridians are on great circles, and the
equator is a great circle. Other lines of
latitude are not great circles, because they are smaller than the equator, their centers are not at the center of the Earth. Great circles on Earth are roughly 40,000 km in length, though the Earth is not a perfect sphere; for instance, the equator is 40,075 km.
Some examples of great circles on the
celestial sphere include the
horizon , the
celestial equator, and the
ecliptic.
Great circle routes are used by ships and aircraft where currents and winds are not a significant factor. For aircraft traveling westerly between continents in the northern hemisphere these paths will extend northward near or into the arctic region, while easterly flights will often fly a more southerly track to take advantage of the
jet stream.
See also
...
Resources
- Great Circle description, figures, and equations. Mathworld, Wolfram Research, Inc. c1999
- Interactive tool for plotting great circle routes.
- deriving course and distance between two points.
