A

David

Darling

geodesic

A geodesic is a path on a given surface that is as straight as possible; in other words, a path that doesn't deviate either to the left or to the right, and only bends when forced to do so by the curvature (if any) of the surface. If the surface is an ordinary plane, the geodesics are straight lines; on a sphere the geodesics are great circles.