The Colour of Magic

23

It is physically impossible for convex octagons (the ones we usually think of when we hear the word ‘octagon’) to tile a plane. Unless, of course, space itself would somehow be strangely distorted (one of the hallmarks of Lovecraft’s Cthulhu mythos). It is possible, however, to tile a plane with non-convex octagons (and Terry nowhere says or implies he meant convex tiles). Proof is left as an exercise to the reader.