Great Circle
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Definition
A great circle is any circle on a sphere whose center coincides with the sphere's center, representing the shortest possible path between two points on the surface.
Explanation
On Earth, great circles include the equator and all lines of longitude. A flight from Los Angeles to London appears to arc northward over Greenland on a flat map — that path is actually shorter than flying due east because it follows a great circle. The concept is essential to aviation route planning; flying a great-circle route between distant cities can save hundreds of kilometers and significant fuel.
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