Essential Relativity: Special, General, and Cosmological (Texts and Monographs in Physics)

As a modern textbook in the theory of relativity, this book is rare, in that its goal is to give the reader a conceptual introduction to the theory, and not just mathematical formalism. The author also does not hesitate to include some philosophical argumentation wherever needed. It is written for the advanced undergraduate, and will prepare such a reader for more advanced reading in the subject. The first chapter of the book is the best, for it is a comprehensive discussion of the origins of the theory of relativity as one that rejected the assertion that space and time were absolute. The author also gives an interesting historical discussion of Lorentz's ether theory, wherein Lorentz hypothesized that bodies moving through the ether undergo a contraction, and he discovered a time transformation that implied that clocks moving through the ether run slow. As the author points out, Lorentz thought such considerations were purely mathematical, and not important physically. In addition, in the section on Mach's principle, the author discusses briefly the work of Dennis Sciama who showed that the 1872 gravitational theory of F. Tisserand included Mach's principle. I was not aware of this work, and it motivated me to do further reading on the subject. The author also gives several examples to show that Mach's principle is not physically vacuous, but has observational consequences. Chapter two overviews the kinematic consequences of the special theory of relativity. The most interesting part of this discussion was the section on the formulation of special relativity without assuming the invariance of the speed of light. The author shows that the principle of relativity implies that either all inertial frames are related by Galilean transformations, or all are related by Lorentz transformations with the same (postive) velocity (squared). A discussion of optical effects follows in chapter 3. One unexpected and interesting result in this chapter is that a moving sphere has a circular outline to all observers because of length contraction. Some of the mathematical formalism needed in special relativity is overviewed in chapter four. The class of four-vectors and four-tensors is defined, and the light cone geometry discussed in detail. The relativistic mechanics of point particles is covered in chapter five. Such a theory is cast in the language of four-vectors, and the author explains nicely the mass-energy equivalence, analyzes scattering from a relativistic standpoint in the center of momentum frame, and shows how Newtonian mechanics is altered in the relativistic realm. He also spends a little time on relativistic continuum mechanics, via the energy tensor of the simplest continua: dust. The connection between relativity and electrodynamics is outlined in chapter six. The material is standard and found in most books on relativity. The author begins the study of general relativity in chapter seven with some elementary considerations of the differential g

This is a wonderful book, very amusing and thought provoking. Without trying to be comprehensive, it sheds much light on the basics of the theory, as well as of the mathematics. His discussion of Mach's principle is brilliant, and ends with a proposal of an experiment to test it with satellites! Very good at computations too, boasting tables for computing the curvature tensor from the metric tensor which are very useful.

Although not the most comprehesive text on the subject (see Thorne's tome, Gravitation), Essential Relativity is perhaps the most fulfilling book from which to learn both special and general relativity on a graduate school level. Flipping through the pages, one cannot help but notice that it often reads like a novel. For the student or the adventurous, a wide variety of problems are found in an appendix. The author's background in differential geometry is very evident in his excellent explanations of difficult concepts.