'The Road to Reality' is a book on modern physics by the British mathematical physicist Roger Penrose, published in 2004. It covers the basics of the standard model of modern physics, discussing general relativity and quantum mechanics and then expands on the possible unification of these two theories.

The book is just over 1100 pages, of which the first 350 are dedicated to mathematics - Penrose`s goal was to acquaint inquisitive readers with the mathematical tools needed to understand the remainder of the book in depth. On page 383 physics enters the discussion with the topic of spacetime. From there it moves on to fields in spacetime, deriving the classical electrical and magnetic forces from first principles; that is, if one lives in spacetime of a particular sort, these fields develop naturally as a consequence. Energy and conservation laws appear in the discussion of the Lagrangians and Hamiltonians, before moving onto a full discussion of quantum physics, particle theory and quantum field theory. A discussion of the measurement problem in quantum mechanics is given a full chapter; superstrings are given a chapter near the end of the book, so is loop gravity and twistor theory. The book ends with an exploration of other theories and possible ways forward.

The book discusses the physical world. Many fields that scientists in the 19th century believed were separate, electricity and magnetism for instance, are facets of a single property, electromagnetism. Some texts, both popular and university level, introduce these topics as separate concepts and then 'force' the combination on them much later. In 'Road to Reality' this process is reversed, by first demonstrating the mathematics that is needed to discuss the spacetime we appear to live in, then showing that electromagnetism simply falls out fully formed.

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