where V is the volume of the container. On the other hand, the likelihood of finding pairs of objects at given positions (i.e. the two-body probability density) is not uniform. For example, pairs of hard balls must be separated by at least the diameter of a ball. The pair distribution function g ( r → → , r → → ′ ) is obtained by scaling the two-body probability density function by the total number of objects N and the size of the container: