Why on earth do cars have the same symmetry as dragonflies? Is there really a beautiful swirling pattern lurking in every dripping tap? What do insect eggs have in common with planets, and why?    In this beautiful little mathematical history book, Welsh writer and artist David Wade paints a picture of one of the most elusive and pervasive concepts known to man.     Introducing the main principles of symmetry, and showing how, despite opinions over exactly what it is, symmetry underlies almost every aspect of nature and our experience of the world, from the subatomic realms of quantum mechanics to the equations of physics, in art, architecture and our concepts of morality and justice.     This symmetry book is one of many art books available from the National Gallery, which include art history books, art exhibition catalogues and gift books.