Spherical geometry

Spherical geometry is the use of geometry on a sphere. It was started for cartography, as well as for making maps of stars. It is different from Euclidean geometry (which is always on a plane), and Non-Euclidean geometry. Points are defined in the same way as they are in Euclidean geometry: A point is at a defined location on the sphere. A "staight line" is different though: It is the shortest path between two points, which stays on the surface of the plane. Some theorems of Euclidean geometry cannot be used on the sphere, many of them have been adapted though.