Bohr and Einstein: Einstein and Bohr 2. The peace before the quantum 3. A glance at relativity 4. The slow rise of the quantum 5. Bohr: what does it all mean? 6. Einstein's negative views 7. Bohm, Bell and experimental philosophy 8. A round-up of recent developments 9. Bohr or Einstein? References Bibliography.
Quantum theory, the most successful physical theory of all time, provoked intense debate between the twentieth century's two greatest physicists, Niels Bohr and Albert Einstein. Quantum information theory has emerged from intensive study of the structure and interpretation of quantum theory to become one of the fastest growing areas of twenty-first century science. This second edition has been extensively revised and updated to cover recent developments, including the findings of papers published since the well-received first edition. A substantial new chapter is devoted to the development and structure of quantum information theory. Developments in the experimental and theoretical study of Bell's Theorem are also covered in detail, and the accounts of ongoing work have been brought up to date. A fascinating account of the development of quantum theory, this book will appeal to anyone with an interest in the fundamental questions of physics, its philosophy and its history.
In this last chapter I shall attempt a very brief assessment of the Bohr–Einstein debate. Who won it in the view of the audience? Who actually had the better case? I will also ask two rather more specific questions. The first is ‘Have the contributions of John Bell favoured the position of either of the protagonists?’ The second is ‘Has the dramatic arrival and progress of quantum information theory anything to tell us about the Bohr–Einstein debate?’ To help to answer these questions, let me first re-assemble a few points, putting together in turn an argument for each of the protagonists against a rather hostile critic. First Bohr, and I take as his critic John Bell himself. Bell was prepared, in fact, to give Bohr great credit for what Bell called the pragmatic approach to quantum theory, which I discussed earlier. This approach says that the world must be divided into ‘classical’ and ‘quantum’ parts, with an arbitrarily placed cut between them; that the macroscopic measuring device must be described in classical terms, but that we should not expect to picture the ‘quantum’ system in physical terms, and should be content just to possess rules of calculation that work well. But Bell regarded Bohr's philosophy of what lay behind pragmatism, complementarity , as ill-defined, unsatisfactory and bizarre.
th century ‐ the theory of relativity and the quantum theory. Based on these developments, it is interesting for the future of physics that when examined in terms of their conceptual and mathematical bases, these theories are incompatible. On the other hand, each of these theories requires an incorporation of the other to proceed toward its completion. This is the dilemma we face in these early decades of the 21 st century: Which of the two theories should be abandoned and which should be maintained?[1] Albert Einstein was the leading proponent of the theory of relativity and its philosophy, Niels Bohr was the leading proponent of the quantum theory and its philosophy ‐ as fundamental theories of matter.[2] Because of the incompatibility of the mathematical and conceptual bases of these theories, in fundamental terms, as will be discussed in detail later on, they cannot peacefully coexist. But because aspects of each of these theories are necessary to complete the other, the form of the accepted theory must be generalized in such a way that it yields, as a mathematical approximation, the form of the theory whose concepts are abandoned. This is an appeal to the wellknown principle of correspondence. Bohr appealed to this principle in showing how the formal expression of quantum mechanics goes smoothly into the structure of classical mechanics as the fundamental unit of action ‐ Planck’s constant h ‐ approaches zero, compared with the values of classical action. Similarly, the principle of correspondence reveals how Einstein’s relativistic mechanics goes smoothly
This book gives a clear and comprehensive exposition of Niels Bohr's philosophy of physics. Bohr's ideas are of major importance, for they are the source of the Copenhagen interpretation of quantum physics; yet they are obscure, and call for the sort of close analysis that this book provides. The book describes the historical background of the physics from which Bohr's ideas grew. The core of the book is a detailed analysis of Bohr's arguments for complementarity and of the interpretation which he put upon it. Special emphasis is placed throughout on the contrasting views of Einstein, and the great debate between Bohr and Einstein is thoroughly examined. The book traces the philosophical influences on Bohr, and unravels the realist and anti-realist strands in his thinking. Bohr's philosophy is critically assessed in the light of recent developments in the foundations of quantum physics (the work of Bell and others) and in philosophy (the realism-anti-realism debate) and it is revealed as being much more subtle and sophisticated than it is generally taken to be. While the book will be of interest to specialists, it is written in a style that will make it accessible to those who have no specialist knowledge of the relevant physics and philosophy.
The debate between Bohr and Einstein on the consistency, completeness, and finality of quantum theory ranks as one of the most significant philosophical debates of the twentieth century. It was a philosophical debate not in the sense that it had a considerable impact on the relatively technical field of the philosophy of physics. It was philosophical because at its root there lay two rival conceptions of physical reality and of our capacity to comprehend physical reality. With the possible exception of the Leibniz-Clarke correspondence in which Leibniz and Clarke - with the latter acting as Newton's frontman - pressed their respective conceptions of space and time in the early part of the eighteenth century, the Einstein-Bohr dialogue has no parallel in the history of physics. Unlike the Leibniz-Clarke correspondence, the Bohr-Einstein debate contained no bitterness and was not based on any personal rivalry. The debate was continuous from about 1927 and lasted right up to Einstein's death in 1955. For the contemporary philosopher of physics the most important episodes took place in the years between 1927 and 1935. However, in one respect at least the differences between Bohr and Einstein predated quantum mechanics itself. One is tempted to view the disagreement between Bohr and Einstein as the opposition of Bohr the revolutionary and Einstein the conservative, and in his best and clearest account of it Bohr certainly writes as if that were so.