It’s said that vampires suffer from a syndrome called arithmomania or an obsessive love of counting, so much so that to escape a vampire you just need to throw loads of cloves of garlic on the floor and the vampire can’t resist counting them, allowing you to make a hasty exit. It was this obsession with counting that inspired my favourite Muppet character, the vampire Count von Count. But I’m actually not in Transylvania to track down vampires but another local inhabitant who was obsessed with mathematics: János Bolyai. At the age of 21 this brilliant mathematician discovered that Euclid’s geometry was not the only possible geometry. He constructed a totally consistent universe where triangles have angles that add to less than 180 degrees and parallel lines do strange things that Euclid never thought possible.