Modern physics has revealed the universe as a much stranger place than we could have imagined. The puzzle at the centre of our knowledge of the universe is time. Michael Lockwood takes the reader on a fascinating journey into the nature of things. He investigates philosophical questions about past, present, and future, our experience of time, and the possibility of time travel. And he provides an introduction to the physics of time and the structure of the universe. He guides us step by step through relativity theory and quantum physics, introducing and explaining the ideas of Newton and Boltzmann, Einstein and Schroedinger, Penrose and Hawking.