Tuesday, August 26, 2008
The nature of the Great Circle route
A great circle is a circle on the surface of a sphere that has the same circumference as the sphere, dividing the sphere into two equal hemispheres, says Wikipedia.
A great circle is the largest circle that can be drawn on a given sphere. The diameter of a great circle is same as the diameter of the sphere.
When long distance aviation or nautical routes are drawn on a flat map (for instance, the Mercator projection), 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 -- they are small circles instead.