Explore a variety of fascinating concepts relating to the four-color theorem with an accessible introduction to related concepts from basic graph theory. From a clear explanation of Heawood’s disproof of Kempe’s argument to novel features like quadrilateral switching, this book by Chris McMullen, Ph.D., is packed with content. It even includes a novel handwaving argument explaining why the four-color theorem is true.What is the four-color theorem?Why is it common to work with graphs instead of maps?What are Kempe chains?What is the problem with Alfred Kempe’s attempted proof?How does Euler’s formula relate the numbers of faces, edges, and vertices?What are Kuratowski’s theorem and Wagner’s theorem?What is the motivation behind triangulation?What is quadrilateral switching?What is vertex splitting?What is the three-edges theorem?Is there an algorithm for four-coloring a map or graph?What is a Hamiltonian cycle?What is a separating triangle?How is the four-color theorem like an ill-conditioned logic puzzle?Why is the four-color theorem true?What makes the four-color theorem so difficult to prove by hand?