Twenty years ago, it was possible to write a book on the foundations of quantum mechanics in which the Everett interpretation was relegated to a footnote Maudlin , p. That would be unthinkable today, in large part because of the work of David Wallace. Nobody has done more to defend, clarify and advance the Everett interpretation over the past dozen years than Wallace, and this book is the culmination of his work on this area. As those who have read Wallace's articles will expect, it is an excellent book, and should be required reading for anyone interested in the foundations of quantum mechanics. The trouble with quantum mechanics is that it doesn't provide us with unique outcomes to our experiments.
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Other editions. Enlarge cover. Error rating book. Refresh and try again. Open Preview See a Problem? Details if other :. Thanks for telling us about the problem. Return to Book Page. Preview — Emergent Multiverse by David Wallace. The Emergent Multiverse presents a striking new account of the "many worlds" approach to quantum theory. The point of science, it is generally accepted, is to tell us how the world works and what it is like.
But quantum theory seems to fail to do this: taken literally as a theory of the world, it seems to make crazy claims: particles are in two places at once; cats are ali The Emergent Multiverse presents a striking new account of the "many worlds" approach to quantum theory. But quantum theory seems to fail to do this: taken literally as a theory of the world, it seems to make crazy claims: particles are in two places at once; cats are alive and dead at the same time. So physicists and philosophers have often been led either to give up on the idea that quantum theory describes reality, or to modify or augment the theory.
The Everett interpretation of quantum mechanics takes the apparent craziness seriously, and asks, "what would it be like if particles really were in two places at once, if cats really were alive and dead at the same time?
Once dismissed as absurd, it is now accepted by many physicists as the best way to make coherent sense of quantum theory. David Wallace offers a clear and up-to-date survey of work on the Everett interpretation in physics and in philosophy of science, and at the same time provides a self-contained and thoroughly modern account of it--an account which is accessible to readers who have previously studied quantum theory at undergraduate level, and which will shape the future direction of research by leading experts in the field.
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Lists with This Book. Community Reviews. Showing Average rating 4. Rating details. More filters. Sort order. If you're into stuff like this, you can read the full review. If one accepts the truthiness of the eigenstate-eigenvalue link it follows that if states are relative, then so are the values of observables.
Not accepting this. What have we got here? If an observable has got a value at a certain moment, is that observable-relative or not? There always being "something" is what shivers my timbers. I know they say energy is eternal but what is energy? If you're into weird stuff, read on. View all 7 comments. Recommended to Manny by: Simon. Shelves: linguistics-and-philosophy , science , science-fiction , well-i-think-its-funny , multiverse , received-free-copy.
If you've been paying any attention, you must already have at least a vague idea of what the Many-Worlds Interpretation of Quantum Mechanics is about. There is not just a single universe, there are a huge number of them, and new ones are constantly splitting off.
But can something that's been this enthusiatically embraced by the SF community If you've been paying any attention, you must already have at least a vague idea of what the Many-Worlds Interpretation of Quantum Mechanics is about. But can something that's been this enthusiatically embraced by the SF community really be respectable?
In his impressive book, David Wallace argues persuasively that it is. It's not merely a good alternative to conventional interpretations of quantum mechanics; he claims it's the only one that gives us a view of what's going on which makes intuitive sense, and doesn't involve the addition of unprovable or downright mystical ideas like "the collapse of the wavefunction" or "the essential role of consciousness".
One's first reaction may well be to label this as paradoxical or willfully contrarian, but Wallace, who has PhDs in both physics and philosophy, lays out his reasoning with skill. Since it's easy to get lost in the many details, I will focus here on two clever analogies which he uses throughout. The first is the heliocentric revolution Copernicus and Galileo ; the second is dinosaurs.
Let's look first at the heliocentric hypothesis. The book opens with a thought-provoking quote from Wittgenstein: what would it have looked like if it had looked like the Earth went round the Sun? Stop and consider that for a moment.
The answer, of course, is that it would have looked exactly the same. Every piece of factual evidence people had, which convinced them that the Sun went round the Earth, could equally well have been interpreted in the opposite direction. At the end of the day, the main reason why people were so slow to agree with Copernicus was a simple one.
His idea was so goddamn weird that it couldn't possibly be correct. Similarly with the Many-Worlds Interpretation. Wallace's argument is that this is just the most straightforward way to make sense of the underlying mathematics of quantum theory, which everyone agrees on. The result is that the cat's state becomes quantum-entangled with everything else, including any observer who may be present.
The math represents this as the sum of two algebraic terms: one stands for the live cat, plus everything else in the world; the other stands for the dead cat, plus everything else in the world.
The two terms rapidly "decohere", in other words cease to influence each other. The basic claim of the Many-Worlds Interpretation is that this is best conceptualized as saying that the universe splits into two copies. That's what the math seems to be telling us: why not believe it? Yet, somehow, most people seem reluctant to take this final step. It's too goddamn weird.
What do they do instead? The most common alternative is "shut up and calculate": use the equations, since they certainly appear to work, but don't worry about what they mean. Indeed, throw out the question as irrelevant and positively distracting. So over to the dinosaurs. As Wallace says, suppose people applied the same kind of reasoning to paleontology. There are fossils; everyone agrees on that. Fossils are bits of rock which you can touch. There are consistent patterns in many of these bits of rock, and the only sensible way of explaining these patterns is to say that their appearance is as it would have been if there once had been dinosaurs.
Just about everyone agrees on that too. But suppose now that you're talking to a creationist petroleum geologist I presume such people may exist , who stops at this point and says that there were in fact no dinosaurs; they are just a theoretical device that helps us categorise fossils.
You would have a hard time refuting this argument. Our hypothetical geologist would agree with everything you said about the links between fossils and dinosaurs, and in fact she would probably know rather more about it than you did, since it was part of her job. She just wouldn't agree that the dinosaurs actually existed. Needless to say, you would find this person intensely irritating; you would be sure they were wrong, even if you couldn't prove it.
Well: the argument here is that we've been doing exactly the same thing in rejecting the Many-Worlds Interpretation. Quite apart from the content, the style of the book is also interesting, and is constructed as an ingenious piece of homage to Wallace's great predecessors. Stylistically, Copernicus and Galileo were polar opposites: Copernicus was a dry, technical writer, and Galileo was an entertaining polemicist.
Copernicus was extremely conservative, and worked entirely within the Ptolemaic system. As Rovelli remarks in his recent book on Anaximander, no one could have loved Ptolemy more than Copernicus did. His intention was simply to show that Ptolemy's deferents and epicycles worked even better if you moved the Sun to the center of the universe. Galileo, in contrast, wanted to shake things up and introduce genuinely new ideas.
Wallace has daringly attempted to mix these two very different styles. Rather more than two-thirds of the book is Copernican, and consists of lengthy technical proofs; the most important ones have to do with the concept of rational behavior in the quantum multiverse, where it is easy to become confused and think that, since everything is going to happen in some branch, it makes no difference what you do.
Wallace shows that this is absolutely not true. In fact, the concept of "branch weight" plays a role exactly analogous to that of probability in a classical theory, and rational agents end up doing what they would have done in a classical universe. Establishing this apparently trivial conclusion unfortunately requires over fifty pages of difficult mathematics. If all the book were like this, it would have been unreadable; despite its honored place in the history of science, it is notorious that hardly anyone has ever read De revolutionibus orbium coelestium.
Wallace has addressed this problem by adding a parallel thread written in an engagingly Galilean style, where he explains the intuitive consequences of the ideas in everyday language. The layman will no doubt want more Galileo; on the other hand, the Copernicus is necessary to convince the many sceptical experts, none of whom appear yet to have detected obvious holes.
The Emergent Multiverse: Quantum Theory according to the Everett Interpretation
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The book is in three parts. Part I explains how quantu Part I explains how quantum theory implies the existence of an emergent branching structure in physical reality, and explores the conceptual and technical details of decoherence theory, the theory which allows us to quantify that branching. Part III explores the implications of an Everettian perspective on a variety of topics in physics and philosophy. Keywords: emergence , Everett , quantum theory , metaphysics , probability , physics. Forgot password? Don't have an account?