Geometry is the discipline devoted to the study of space and the rules relating the elements to each other. For example, in Euclidean space the Pythagorean theorem provides a rule to compute distances from Cartesian coordinates. In a two-dimensional space of constant curvature, like the surface of a sphere, the rule is somewhat more complex but applies everywhere. On the two-dimensional surface of a football, the rule is more complex still and has different values depending on location. In well-behaved spaces such rules used for measurement, called metrics, are classically handled by the mathematics invented by Riemann. Object space belongs to that class.
