Lets say you have a sphere and you put two points on that sphere such that a line connecting those two points would be the diameter of the sphere and you call these points point A and point B respectively. you're now a flatlander (2D creature) on that sphere as he walks across the sphere, you imagine the center of this flat-land is point A, if a flatlander walks in any direction from point A he'll always reach point B. So to the flatlander, point B has become a PERIMETER, we've changed a 0 dimensional object into a two dimensional object by just reinterpreting how we see the shape, it just seems really weird to me.