The Tum of the Tide During centuries physicists were supposed to be studying the physical world. Since the turn of the century this assumption has often been challenged as naive: it was proclaimed that physics is not about the external world but about observers and their manipUlations: that it is meaningless to talk of anything else than observation devices and opera tions: that the laws of physics concern our knowledge rather than the external world. This view of the nature of physical science has old roots in philo sophy but it was independently reinvented by a number of philosophi cally inclined physicists, notably ERNST MACH. These scientists were disgusted with the school philosophies and they were alarmed by the increasing number of physical concepts which they regarded as meta physical or beyond experimental control, such as those of absolute motion, ether, electromagnetic field, and molecule. Reasonably enough, they wished to keep physics testable. To accomplish this goal they adopted the safe method, namely to banish every idea that could not be closely tied to observation. In this way they certainly avoided the risks of untestable speculation but they also failed to enjoy the benefits of theoretical invention. Furthermore they instituted unawares a new meta physics that was to dominate the philosophy of physics for half a century: the metaphysics according to which the world is made of sense experience.

This clearly explained layman's introduction to quantum physics is an accessible excursion into metaphysics and the meaning of reality. Herbert exposes the quantum world and the scientific and philosophical controversy about its interpretation.

What does realism about the quantum state imply? What follows when quantum theory is applied without restriction, if need be, to the whole universe? These are the questions which an illustrious team of philosophers and physicists debate in this volume. All the contributors are agreed on realism, and on the need, or the aspiration, for a theory that unites micro- and macroworlds, at least in principle. But the further claim argued by some is that if you allow the Schrödinger equation unrestricted application, supposing the quantum state to be something physically real, then this universe is one of countlessly many others, constantly branching in time, all of which are real. The result is the many worlds theory, also known as the Everett interpretation of quantum mechanics. The contrary claim sees this picture of many worlds as in no sense inherent in quantum mechanics, even when the latter is allowed unrestricted scope and even given that the quantum state itself is something physically real. For this picture of branching worlds fails to make physical sense, let alone common sense, even on its own terms. The status of these worlds, what they are made of, is never adequately explained. Ordinary ideas about time and identity over time become hopelessly compromised. The concept of probability itself is brought into question. This picture of many branching worlds is inchoate, it is a vision, an error. There are realist alternatives to many worlds, some even that preserve the Schrödinger equation unchanged. Twenty specially written essays, accompanied by commentaries and discussions, examine these claims and counterclaims in depth. They focus first on the question of ontology, the existence of worlds (Part 1 and 2), second on the interpretation of probability (Parts 3 and 4), and third on alternatives or additions to many worlds (Parts 5 and 6). The introduction offers a helpful guide to the arguments for the Everett interpretation, particularly as they have been formulated in the last two decades.

Quantum mechanics is an extraordinarily successful scientific theory. It is also completely mad. Although the theory quite obviously works, it leaves us chasing ghosts and phantoms; particles that are waves and waves that are particles; cats that are at once both alive and dead; and lots of seemingly spooky goings-on. But if we're prepared to be a little more specific about what we mean when we talk about 'reality' and a little more circumspect in the way we think a scientific theory might represent such a reality, then all the mystery goes away. This shows that the choice we face is actually a philosophical one. Here, Jim Baggott provides a quick but comprehensive introduction to quantum mechanics for the general reader, and explains what makes this theory so very different from the rest. He also explores the processes involved in developing scientific theories and explains how these lead to different philosophical positions, essential if we are to understand the nature of the great debate between Niels Bohr and Albert Einstein. Moving forwards, Baggott then provides a comprehensive guide to attempts to determine what the theory actually means, from the Copenhagen interpretation to many worlds and the multiverse. Richard Feynman once declared that 'nobody understands quantum mechanics'. This book will tell you why.

Albert Einstein was one of the principal founders of the quantum and relativity theories. Until 1925, when Bose-Einstein statistics was discovered, he made great contributions to the foundations of quantum theory. However, after the discovery of quantum mechanics by Heisenberg and wave mechanics by Schrodinger, with the consequent development of the principles of uncertainty and complementarity, it would seem that Einstein's views completely changed. In his theory of the Brownian motion, Einstein had invoked the theory of probability to establish the reality of atoms and molecules; but, in 1916-17, when he wished to predict the exact instant when an atom would radiate -- and developed his theory of the A and B coefficients -- "a statistical residue remained," which he did not quite have the courage of his convictions to accept, as he told his friend Max Born. However, he wrote later to Born that quantum mechanics "is certainly imposing," but "an inner voice tells me that it is not the real thing ... It does,not bring us closer to the secret of the 'Old One'. I, at any rate, am convinced that He is not playing at dice." At the 1927 and 1930 Solvay Conferences on Physics in Brussels, Einstein engaged in profound discussions with Niels Bohr and others about his conviction regarding classical determinism versus the statistical causality of quantum mechanics. To the end of his life he retained his belief in a deterministic philosophy. This highly interesting book explores Einstein's views on the nature and structure of physics and reality.

Probably the most successful scientific theory ever created, quantum theory has profoundly changed our view of the world and extended the limits of our knowledge, impacting both the theoretical interpretation of a tremendous range of phenomena and the practical development of a host of technological breakthroughs. Yet for all its success, quantum t

The book deals with expounding the nature of Reality as it is understood in contemporary times in Quantum Physics. It also explains the classical Indian theory of Śūnya in its diverse facets. Thereafter it undertakes comparison between the two which is an area of great topical interest. It is a cross-disciplinary study by erudite Indian and western scholars between traditional Indian knowledge system and contemporary researches in Physical sciences. It points out how the theory of ‘Śūnyatā has many seminal ideas and theories in common with contemporary Quantum Physics. The learned authors have tried to dissolve the “mysteries” of Quantum Physics and resolved its “weird paradoxes” with the help of theory of Śūnyatā. The issue of non-separability or entanglement has been approached with the help of the Buddhist theory of Pratītyasamutpāda. The paradoxical situation of “wave-particle duality” has been explained with the help of Upaniṣadic theory of complementarity of the two opposites. The measurement problem represented by “Schrodinger’s cat” has been dealt with by resorting to two forms of the calculation of probabilities. Some writers have argued for Śūnyatā-like non-essentialist position to understand quantum reality. To make sense of quantum theory some papers provide a happy symbiosis of technical understanding and personal meditative experience by drawing multifarious parallels. This book will be of interest to philosophically inclined physicists and philosophers with interest in quantum mechanics.