Welcome to Booked!, a feature where we ask an author to share their favorite books with our readers. Today’s guest is Greg Egan, author of The Clockwork Rocket, the first book in the Orthogonal trilogy.
I first heard about black holes as a teenager in the 1970s, and though the idea of an object with gravity so strong that not even light could escape from it came across clearly enough in the pop-science coverage, I yearned to understand what was really going on. Time slowed down, objects seemed to freeze at the event horizon, and some writers even claimed that anything you dropped into a black hole would take an eternity to fall in. The popular accounts didn’t equip me to reason about these exotic phenomena; they just made assertions that had to be taken on trust.
In the 1980s I tried a couple of times to teach myself general relativity, but I chose the wrong books and found myself baffled and dispirited. One textbook proclaimed that a tensor was “a collection of numbers that transformed a certain way” when measured in different coordinate systems. But why did they transform that way? This book left me none the wiser.
It was only in 1996 that I finally came across Gravitation by Charles Misner, Kip Thorne and John Wheeler. Published in 1973, this 1279-page masterpiece takes all the time it needs to prepare the reader for the subject, spelling out the beautiful geometric principles that underly Einstein’s conception of gravity. In general relativity, the way lengths and angles are measured varies from place to place and time to time, so there needs to be an underlying framework in which these concepts can be defined without simply taking them for granted. That framework is known as differential geometry, and once you learn its concepts and tools, black holes, the expanding universe, and other counterintuitive features of modern science finally become comprehensible. This book gives you the mathematics you need, defined with care, but backs it all the way with physical intuition. I only wish I’d read it twenty years earlier.