A Geodesic

A geodesic is the shortest path between two points on a curved surface, such as the surface of a sphere or any other curved space. In Euclidean geometry (flat space), a geodesic is a straight line. However, in curved spaces, the concept of a straight line is generalized to refer to the shortest distance between two points, which is a curve known as a geodesic.

On the surface of a sphere, for example, the geodesics are great circles—circles whose centers coincide with the center of the sphere. These great circles represent the shortest paths between any two points on the sphere's surface. In the context of general relativity, geodesics play a crucial role in describing the paths that objects and light rays follow in curved space-time under the influence of gravity.