Hugh Everett III was an American physicist best known for his many-worlds interpretation of quantum mechanics, which formed the basis of his PhD thesis at Princeton University in 1957. Although counterintuitive, Everett's revolutionary formulation of quantum mechanics offers the most direct solution to the infamous quantum measurement problem--that is, how and why the singular world of our experience emerges from the multiplicities of alternatives available in the quantum world. The many-worlds interpretation postulates the existence of multiple universes. Whenever a measurement-like interaction occurs, the universe branches into relative states, one for each possible outcome of the measurement, and the world in which we find ourselves is but one of these many, but equally real, possibilities. Everett's challenge to the orthodox interpretation of quantum mechanics was met with scorn from Niels Bohr and other leading physicists, and Everett subsequently abandoned academia to conduct military operations research. Today, however, Everett's formulation of quantum mechanics is widely recognized as one of the most controversial but promising physical theories of the last century.

In this book, Jeffrey Barrett and Peter Byrne present the long and short versions of Everett's thesis along with a collection of his explanatory writings and correspondence. These primary source documents, many of them newly discovered and most unpublished until now, reveal how Everett's thinking evolved from his days as a graduate student to his untimely death in 1982. This definitive volume also features Barrett and Byrne's introductory essays, notes, and commentary that put Everett's extraordinary theory into historical and scientific perspective and discuss the puzzles that still remain.

In this book Jeffrey A. Barrett provides an introduction to the history and conceptual foundations of quantum mechanics. He begins with a description of classical mechanics and a discussion of the quantum phenomena that radically undermine our common-sense classical intuitions about how the physical world works. He then considers the physical and conceptual arguments that led to the standard von Neumann-Dirac formulation of quantum mechanics and how the standard theory explains quantum phenomena. This includes a discussion of how the theory's two dynamical laws work with the standard interpretation of states to explain determinate measurement records, quantum statistics, interference effects, entanglement, decoherence, and quantum nonlocality. A careful understanding of how the standard theory works ultimately leads to the quantum measurement problem. Barrett considers how this problem threatens the logical consistency of the standard theory and then turns to a discussion of the main proposals for resolving it. This includes collapse formulations of quantum mechanics, the various many-worlds theories, and Bohmian mechanics. In discussing alternative formulations he pays particular attention to the explanatory role played by each theory's empirical ontology and associated metaphysical commitments, and the conceptual trade-offs between theoretical options. The book is well-suited to those interested in physics and the history and philosophy of quantum mechanics.

Jeffrey Barrett presents the most comprehensive study yet of a problem that has puzzled physicists and philosophers since the 1930s. Quantum mechanics is in one sense the most successful physical theory ever, accurately predicting the behaviour of the basic constituents of matter. But it has an apparent ambiguity or inconsistency at its heart; Barrett gives a careful, clear, and challenging evaluation of attempts to deal with this problem.

In this book Jeffrey A. Barrett provides an introduction to the history and conceptual foundations of quantum mechanics. He begins with a description of classical mechanics and a discussion of the quantum phenomena that radically undermine our common-sense classical intuitions about how the physical world works. He then considers the physical and conceptual arguments that led to the standard von Neumann-Dirac formulation of quantum mechanics and how the standard theory explains quantum phenomena. This includes a discussion of how the theory's two dynamical laws work with the standard interpretation of states to explain determinate measurement records, quantum statistics, interference effects, entanglement, decoherence, and quantum nonlocality. A careful understanding of how the standard theory works ultimately leads to the quantum measurement problem. Barrett considers how this problem threatens the logical consistency of the standard theory and then turns to a discussion of the main proposals for resolving it. This includes collapse formulations of quantum mechanics, the various many-worlds theories, and Bohmian mechanics. In discussing alternative formulations he pays particular attention to the explanatory role played by each theory's empirical ontology and associated metaphysical commitments, and the conceptual trade-offs between theoretical options. The book is well-suited to those interested in physics and the history and philosophy of quantum mechanics.