The Harry Potter books almost have a complete world built in, thanks to seven books, several tie-ins, and, for better or for worse, whatever author J.K. Rowling decided to introduce in Pottermore. Despite all the detail that has gone into crafting his universe, there are still some things that can’t be accounted for—things that keep Potterheads up at night (Literally. A roommate and I spent two hours trying discussing the logistics of the first entry on the list).
Source: io9 – 5 Things From Harry Potter That Will Probably Never Be Explained