This is a typically well written and clear exposition of its subject by John Gribbin, one of our finest popular-science authors and a professional astronomer to boot. Einstein’s Masterwork: 1915 and the General Theory of Relativity explains in everyday language how Einstein accounted for gravity’s effects on spacetime summed up in an equation which is far less famous than the E=MC2 of his ‘annus mirabilis‘ in 1905 (his Nobel Prize-winning paper on Brownian motion, his doctoral thesis for the University of Zurich on calculating the sizes of molecules and atoms suspended in a fluid, his paper on the photoelectic effect that explained black-body radiation and proved that light and matter behave in fundamentally the same ways, establishing the reality of light quanta, and the now famous paper on the Special Theory of relativity) but no less important: gμν (gee mu nu).
The possibility that the universe is curved had been posited earlier and independently by the mathematicians Riemann and Clifford. Minkowski had elaborated on the Special Theory, which applies to a notional flat spacetime, with his spacetime diagram, describing how a vector moves along its own timeline relative to constant spacetime. It is a pictorial representation of how inertial frames of reference in uniform motion relate to each other in the Special Theory. The General Theory goes much further by accounting for the acceleration in 4-dimensional curved spacetime of tensors (the non-Euclidean version of the vector). The difference is that the presence of matter creates the curvature of spacetime, and the tensors, of which there may be as many as 16, describe this curvature. Fortunately for the curious general reader, such as myself, who has no background in higher mathematics or cosmology, this is all laid out in a refreshingly straightforward scheme that requires no headache-inducing attempts to grasp equations. Indeed, it is almost tempting to wonder what is so terribly difficult about all this stuff about spacetime curvature, gravitational lensing and all the rest of it, so lucid is Gribbin’s treatment of the material.
There is an illuminating though necessarily not comprehensive account of Einstein’s personal life as it related to his work (after all, the book is about a specific aspect of his work, not a full-blown biography), enough to show the real human being behind the image of the secular saint and omniscient genius. It shows how Einstein’s theories, brilliantly conceived though they are, did not emerge ex nihilo; his great predecessors such as Maxwell, Boltzmann, Planck, Minkowski, et al were working in a scientific culture that grows out of the ingenuity of many minds. However, the singular genius of Albert Einstein shines through. It has been said that the Special Theory would have been developed by somebody around that time if Einstein had not done so; but the General Theory could probably only have been produced by his uniquely fertile imagination. The book ends with an account of the scientific legacy of the General Theory (black holes, time dilation, wormholes, etc) and Einstein’s final years.
This book is pitched at a level which the non-specialist can appreciate without being condescending or irritatingly chummy. It deals with complex ideas that have profoundly changed our understanding of the universe’s structure and workings, ideas which will continue to affect humanity’s future in ways we can only guess at. If you want to get Einstein’s work, get this book.