comes from our (understandably) contorted attempts to find pictures for visualizing it or stories to tell about it. Quantum physics defies intuition, but we do it an injustice by calling that circumstance 'weird'.Quantum mechanics has the reputation of being probably the most obscure and difficult branch of science, but Ball insists that it isn't 'hard' in the way that car maintenance or learning Chinese are hard (his examples). That isn't to say that a slight readjustment of our intuitions will make everything suddenly explicable. 'Indeed, it is possible that we might never be able to say what quantum theory "means".'
Ball offers new ways of looking at all the hoary old chestnuts of popular accounts of quantum science: the double slit experiment, Schrödinger's cat, entanglement and non-locality (Einstein's 'spooky action at a distance') and the rest. On all these topics he makes one question the ideas one has acquired by reading popular accounts of them previously. His approach is based on work by a number of physicists in the last decade or two.
A central problem we are always told about in books of this kind concerns how the classical world of everyday objects, including us, emerges from the mysterious quantum world. This occurs thanks to something cryptically described as 'collapse of the wave function'. Ball seeks to explain this, and much else, in terms of information. Quantum experiments take place within a wider classical environment, and what happens is that 'information gets out of the quantum system and into the macroscopic apparatus'.
There's then no longer any need for an ambiguous and contentious division of the world into the microscopic, where quantum rules, and macroscopic, which is necessarily classical. We can abandon the search for some hypothetical 'Heisenberg cut' where the two worlds impinge. We can see not only that they are a continuum but also why classical physics is just a special case of quantum physics.On this interpretation there is no need for the radical 'many worlds' solution famously proposed by Hugh Everett III, according to which the world is continually splitting into different branches, in which innumerable copies of each of us continue to pursue different destinies. Ball treats this theory at some length and concludes that it is both unnecessary and unworkable.
Although this is mostly a book about theories, it does contain a quite lengthy discussion of quantum computers. This is included both as an illustration of the practical importance of quantum physics and also because Ball thinks that the questions it raises help to illuminate quantum physics. Perhaps the most striking thing to emerge from this is the fact that no one is entirely sure how these machines actually work. _
Ball is an experienced writer and he treats his subject with a light and often humorous touch, so the book isn't heavy reading even though one has to take it slowly because of the complexity and unfamiliarity of many of the ideas. Ball's usual method of approaching these is a little like a Socratic dialogue. Instead of coming straight out with what he thinks, he proposes possible answers to questions and then shows why they won't do, before offering an alternative; sometimes there are several stages in this process.
I've read a good many popular accounts of quantum theory in the past and had decided that I felt no great inclination to embark on any more. But I made an exception in this case and am glad I did, because I found I was genuinely being given a different way of thinking about the apparent paradoxes that swirl about the subject.