Physics has a dark secret at its heart. The two big theories that form the main basis of just about everything don’t work together. Quantum theory, dealing with the very small, and general relativity, dealing with gravity and the nature of space-time, are incompatible. Not only does this make it impossible to put together a coherent theory covering, for instance, all forces, it messes up our understanding of events that fit into both camps, like the big bang.
The best known modern attempt to pull the two together is string theory – but this has huge problems as far as making useful predictions goes, and some regard it as a dead end. Its main opposition (though there are other theories) is loop quantum gravity. This breaks down space-time itself into atoms, which have something of a loop-like nature, making reality a kind of weave of these loops.
This theory too has yet to make any useful predictions, and like string theory it depends on mind-twistingly complex maths. Yet it is in some ways simpler, doesn’t need many extra dimensions to make it work and even gets around some of the concerns about infinities cropping up at the big bang.
This means we desperately needed a good, popular science guide to string theory – and sadly we still do. Martin Bojowald is one of the key figures in the field, and certainly has a good grasp on the science, but has real problems with getting the information across. It probably doesn’t help that this book was first written in German, then translated into English by the author – certainly at times you might think it still isn’t English.
The science simply hasn’t been made understandable. The author spends a fair amount of time, for example, on Penrose diagrams. These special space-time diagrams are very useful to help understand what is happening in a black hole and similar oddities of space time. But it is very difficult to grasp what is going on. We are told that the singularity is not timelike, but spacelike – it is part of evolving space at a fixed time. This is shown clearly on the diagram, but we are given no real explanation of why this is so, or what it means.
It doesn’t help that the book is illustrated by fairly meaningless arty photographs and has occasional snippets of very bad fiction (which presumably are harder to translate than the science). All in all it is a frustrating read that is unlikely to be illuminating unless you already know quite a lot about the subject area, but not about loop quantum gravity.