The Physical World offers a grand vision of the essential unity of physics that will enable the reader to see the world through the eyes of a physicist and understand their thinking. The text follows Einstein's dictum that 'explanations should be made as simple as possible, but no simpler', to give an honest account of how modern physicists understand their subject, including the shortcomings of current theory. The result is an up-to-date and engaging portrait of physics that contains concise derivations of the important results in a style where every step in a derivation is clearly explained, so that anyone with the appropriate mathematical skills will find the text easy to digest. It is over half a century since The Feynman Lectures in Physics were published. A new authoritative account of fundamental physics covering all branches of the subject is now well overdue. The Physical World has been written to satisfy this need.

The book concentrates on the conceptual principles of each branch of physics and shows how they fit together to form a coherent whole. Emphasis is placed on the use of variational principles in physics, and in particular the principle of least action, an approach that lies at the heart of modern theoretical physics, but has been neglected in most introductory accounts of the subject.

Nicholas Manton, *Department of Applied Mathematics and Theoretical Physics, University of Cambridge*,Nicholas Mee, *Director of software company Virtual Image*

Nicholas Manton studied theoretical physics and mathematics at the University of Cambridge and gained his Ph.D. in 1978. Following postdoctoral positions at the Ecole Normale Superieure in Paris; Massachusetts Institute of Technology; and University of California, Santa Barbara, he returned to Cambridge and is now Professor of Mathematical Physics in the Department of Applied Mathematics and Theoretical Physics. He is also head of the department's High Energy Physics group, and a fellow of St John's College. He has taught numerous courses on mathematics and physics, including courses on vector calculus, quantum mechanics, statistical physics, quantum field theory, elementary particles, and supersymmetry. His research has been mainly on solitons in quantum field theory, including magnetic monopoles and vortices, and he has used the solitons known as Skyrmions to model the complicated structure of atomic nuclei.

Nicholas Mee studied theoretical physics and mathematics at the University of Cambridge. He achieved the top distinction in Part III of the Mathematical Tripos of the University of Cambridge and gained his PhD in 1990 in theoretical particle physics, with a thesis titled Supersymmetric Quantum Mechanics and Geometry. He is the Director of software company Virtual Image and the author of over 50 maths and science multimedia titles including The Code Book on CD-ROM with Simon Singh and Connections in Space with John Barrow and Martin Kemp. He is also author of the award-winning popular science book Higgs Force: Cosmic Symmetry Shattered. Nicholas Mee is well-known in the maths education, popular science and amateur astronomy communities, and his physics blog has a large established readership.