Great circle
From Simple English Wikipedia, the free encyclopedia
A great circle is a circle in a sphere that cuts the surface on equal halves called hemispheres. It is a circle that has the same diameter of the sphere it was made out of. This curves are geodesics in the sphere and all have the same circumference, that is, the lenght of the circle.
Great Circles are used to determine the shortest distance between two points on the surface of a sphere (or on the earth). You can find the shortest route between two points on a sphere by drawing a plane (flat surface) that connects the start and end points with the point at the very center of the sphere. The arc along the surface made by that plane would be along a Great Circle.
For instance, imagine looking right down at the north pole on a globe. If you wanted to get from a point 1 inch to the left of the pole over to a point 1 inch to the right of the pole, you would not curve around the pole in a C-shape (staying at a constant latitude). Instead, the shortest route would be one that arcs over the top.
