Quantum theory has passed through three distinct stages during its evolution. The first is generally referred to as ‘old quantum theory’. During a period roughly between 1900 and 1925 Planck, Bohr and Einstein, among others, grappled with various experimental and theoretical crises by patching up classical mechanics with some new quantum ideas applied as band-aids. This is not to disparage the work; it was vitally important, and you can only do what is possible at the time. The quantum world is very different to the picture painted by classical physics. That being the case and given the extreme nature of some of these differences, we might question the wisdom of accepting the quantum view. Scientists can be quite disparaging about philosophy, sometimes while in the process of espousing, quite stridently, a philosophical position of their own. The chapter also presents an overview on the key concepts discussed in this book.
Quantum theory has passed through three distinct stages during its evolution. The first is generally referred to as ‘old quantum theory’. During a period roughly between 1900 and 1925 Planck, Bohr and Einstein, among others, grappled with various experimental and theoretical crises by patching up classical mechanics with some new quantum ideas applied as band-aids. This is not to disparage the work; it was vitally important, and you can only do what is possible at the time. The quantum world is very different to the picture painted by classical physics. That being the case and given the extreme nature of some of these differences, we might question the wisdom of accepting the quantum view. Scientists can be quite disparaging about philosophy, sometimes while in the process of espousing, quite stridently, a philosophical position of their own. The chapter also presents an overview on the key concepts discussed in this book.
From a historical point of view, a distinction can be drawn between ‘old quantum theory’ and the full quantum theory that we now use. Old quantum theory was in essence a patchwork, cobbled together by incorporating some quantum ideas into essentially classical physics. The work of Planck, Einstein, Bohr, and Sommerfeld can be bracketed as old quantum theory. This classification is not meant to undermine the tremendous achievement that old quantum theory represents, but simply to underline its standing as a stage on the way to a fully formed quantum theory, which emerged from the work of Heisenberg, Schrodinger, Born, and Dirac. The development of the photon concept is a key example of a radically new idea gradually gaining acceptance. The process works via a growing realization that more and more things can be explained in the context of the photon model.
Scope of this book Quantum mechanics is a difficult subject, and this book is intended to help the reader overcome the main difficulties in the way to understanding it. The first part of the book, Chs. 2–16, contains a systematic presentation of the basic principles of quantum theory, along with a number of examples which illustrate how these principles apply to particular quantum systems. The applications are, for the most part, limited to toy models whose simple structure allows one to see what is going on without using complicated mathematics or lengthy formulas. The principles themselves, however, are formulated in such a way that they can be applied to (almost) any nonrelativistic quantum system. In the second part of the book, Chs. 17–25, these principles are applied to quantum measurements and various quantum paradoxes, subjects which give rise to serious conceptual problems when they are not treated in a fully consistent manner. The final chapters are of a somewhat different character. Chapter 26 on decoherence and the classical limit of quantum theory is a very sketchy introduction to these important topics along with some indication as to how the basic principles presented in the first part of the book can be used for understanding them. Chapter 27 on quantum theory and reality belongs to the interface between physics and philosophy and indicates why quantum theory is compatible with a real world whose existence is not dependent on what scientists think and believe, or the experiments they choose to carry out. The Bibliography contains references for those interested in further reading or in tracing the origin of some of the ideas presented in earlier chapters.
Now that we have reached the end of our brief tour through the early history of quantum theory, we need to stop and consider some important themes. From a historical point of view, a distinction can be drawn between ‘old quantum theory’ and the full quantum theory that we now use. Old quantum theory was in essence a patchwork cobbled together from classical physics with a few quantum ideas thrown in. e works of Planck, Einstein, Bohr, and Sommerfeld can be classed as old quantum theory. is is not meant to undermine the tremendous achievements that old quantum theory represents, but simply to underline its standing as a stage on the way to a fully formed quantum theory, which slowly emerged from the works of Heisenberg, Schrödinger, Born, and Dirac.
What is 'the nature of reality’? This thought has occupied the minds of scientists and philosophers since time immemorial. This issue is examined scientifically, that, how the views of scientists and western philosophers have undergone a dramatic change over a period of time. This may then answer whether spacetime is a reality of nature or if it is just a figment of our imagination in which to view this cosmos! The article begins with the thoughts of Democritus, and the other Greek philosophers, continuing with the ideas of Copernicus, Galileo and Kepler. With the thoughts of Bacon, Descartes and Isaac Newton, the rise of the ‘mechanical world view’ later the decline of this view is discussed when the phenomenon in optics, electricity and magnetism could not be explained. Then the concept of ‘field’ was evolved, culminating in ‘Maxwell’s equations of electromagnetic fields’.The beginning of twentieth century saw the evolution of the concepts of ‘relativity’, by Einstein, and the birth of ‘quantum theory’, starting with the idea of ‘quanta’, originated by Planck in 1900. The first three decades of the 20th century saw great breakthroughs in the world of theoretical physics - totally new ideas on ‘the nature of reality’ were being conceived. Large numbers of fundamental particles were discovered in the ensuing years. However, not much progress indeed was made in answering some of the most fundamental questions about the existence of human life and the nature of reality. Some interesting ideas on ‘biocentrism’ have now evolved. Biocentrism, along with the ideas of quantum theory and the concept of consciousness, may answer some of the intricate questions about the nature of reality; these will be discussed at length. These concepts will then be viewed from the perspective of Indic thoughts. The ‘Vedic’ and ‘Upanishadic’ knowledge from Indian scriptures may probably answer even more clearly some of the most intriguing questions about the existence of life and the ‘nature of reality’ itself.Beginning of twentieth century saw the evolution of the concepts of ‘Relativity’, by Einstein, and the birth of ‘Quantum Theory’, starting with the idea of ‘Quanta’, originated by Planck in 1900. The first three decades of 20th century saw the great breakthroughs in the world of theoretical physics. Absolutely new ideas on ‘The Nature of Reality’ were being conceived. Large number of fundamental particles was discovered in the ensuing years. But not much progress indeed took place in answering some of the most fundamental questions on existence of human life and the nature of reality. Some interesting ideas on ‘Biocentrism’ have now evolved. Biocentrism along with the ideas of Quantum Theory and the concept of Consciousness may answer some of the intricate questions on nature of reality; these will be discussed at length. These concepts will then be viewed from perspective of Indic thoughts. The ‘Vedic’ and ‘Upanishadic’ knowledge from Indian scriptures may probably answer even more clearly some of the most intriguing questions on the existence of life and the ‘Nature of Reality’ itself.
By questioning the validity of some of our basic concepts, such as space, object, and causality, quantum physics contributes quite decisively to the dramatic changes now taking place in our world picture.This book is addressed not only to physicists at an early stage in their careers (the first or second year graduate student) but also to philosophers, as well as to all the senior physicists interested in the interpretation problem. Beginning with a chapter that could be described as ?philosophy for physicists,? it presents an in-depth analysis of present-day quantum mechanical concepts, an analysis of physicists and philosophers alike. Specifically, it first offers an extensive critical analysis of such topics as the Einstein, Podolsky, Rosen reality criterion, nonseparatability, the quantum measurement riddle, decoherence theory, consistent histories approaches and ontologically interpretable theories. All this then naturally leads to philosophical questions concerning, in particular, intersubjective agreement and the limit of realism. And a thorough examination of this whole material finally leads to the view that distinguishing between empirical reality and a veiled man-independent reality yields an acceptable answer to the perplexing question of how to interpret quantum physics. Veiled Reality offers nonspecialists, including students in physics, philosophy and the history of science, an accessible perspective on basic problems in the foundations of physics.
The ideas in Heisenberg's paper on quantum mechanics in 1925 mark the beginning not only of a new phase in modern physics, but also of Heisenberg's own philosophical journey. This thesis examines that journey between 1925 and the late 1950s by situating Heisenberg's philosophy of quantum mechanics in the context of his encounters with his contemporaries as well as the context of various strands of thought in the German-speaking world at the time. Heisenberg's early philosophical critique of the 'classical' viewpoint between 1925 and 1927 bears the decisive influence of Einstein's theory of relativity, more specifically, the positivism he saw as underpinning Einstein's emancipation from Newtonian physics. The positivist influence on Heisenberg's early attitude to quantum mechanics is evident in three ways: (a) his invocation of an observability principle in 1925 to justify the renunciation of the concept of the electron orbit, (b) an instrumentalist conception of understanding, which characterised Heisenberg's response to Schrodinger's demand for classical visualisation in space and time in 1926-7, and (c) the introduction of an operational definition of concepts such as position and velocity in 1927, in an attempt to replace the concepts of classical physics. But after discussions with Bohr and Einstein in 1926-7, Heisenberg soon recognised what we might term his `empiricist' viewpoint was problematic. In 1927 Heisenberg's thought undergoes a shift away from the `empiricist' viewpoint that had underpinned his early philosophy of quantum mechanics. The nature and scope of this transformation, which forms the central theme in this thesis, has, up until now, been poorly understood and often completely neglected. Through his discussions with Bohr, Heisenberg came to the realisation that despite their limitations, classical concepts were conditions for the possibility of the description of all experience. This marked the abandonment of his earlier attempt to replace classical concepts with quantum concepts. The recognition of the primacy of classical language forms the point of departure for much of Heisenberg's later thought, which brought him into contact with the attempts in the German-speaking world in the 1920s to reconstruct Kantian epistemology. By the mid-1930s, Heisenberg advocated a 'pragmatic transformation' of Kantian philosophy, in which classical concepts were held to be a priori in the sense that they remained the conditions for the possibility of experience, but were no longer held to be necessary or universal in a strict Kantian sense. After 1940 Heisenberg saw the paradoxes of quantum mechanics under the aegis of what can be termed a 'transcendental conception of language', according to which language is not a mere tool, but actively shapes, gives form, and objectifies, our 'reality'. The limits of a classical 'description' in quantum mechanics therefore came to signify for Heisenberg, the limits of 'objective reality'. While Bohr exerted perhaps the most important philosophical influence on Heisenberg, their intellectual relationship was characterised by disagreement and misunderstanding. This is most strikingly displayed in their respective views on wave-particle duality and complementarily. While after 1927 Heisenberg accepted Bohr's basic insight that our knowledge of the quantum world is mediated through classical language, he did not share Rohr's interpretation of complementarity. While Heisenberg certainly used terms such as 'complementarity' and wave-particle duality' in his writings, a close reading reveals that these terms had very different meanings for the two physicists. This is particularly evident in the contrast between Heisenberg's notion of wave-particle equivalence and Bohr's idea of complementarity. In bringing to light these divergences between Bohr and Heisenberg, this thesis lends further weight to the view - already advocated by scholars such as John Hendry and Mara Beller - that the so-called Copenhagen interpretation of quantum mechanics should not be thought of as a unified philosophical position, but actually comprises a number of different strands.