A Topological Aperitif

Topology has been referred to as "rubber-sheet geometry" . The name is apt, for the subject is concerned with properties of an object that would be preserved, no matter how much it is stretched, squashed, or distorted, so long as it is not in any way torn apart or glued together. One's first reaction might be that such an imprecise-sounding subject could hardly be part of serious mathematics, and would be unlikely to have applications beyond the amusement of simple parlour games. This reaction c