What is an imaginary number? Can two parallel lines ever meet? How can maths help us predict the future? Charting the development of maths around the world from Babylon to Bletchley Park, this book explores big questions like these and explains how the answers help us understand everything from patterns in nature to artificial intelligence. Written in clear English, The Maths Book is packed with short, pithy explanations that cut through the jargon, step-by-step diagrams that untangle knotty theories, memorable quotes, and witty illustrations that play with our ideas about numbers. This diverse and inclusive account of mathematics will have something for everybody, including the maths behind world economies and espionage. But it also traces the history of maths, from ancient ideas such as magic squares and the abacus to modern cryptography, fractals, and the final proof of Fermat's Last Theorem. Continuing the "Big Ideas" series' trademark combination of authoritative, clear text and bold graphics, The Maths Book uses an innovative visual approach to make the subject accessible to everyone, whether you're an avid student or just curious about maths.