History of Quantum Mechanics

It has been argued that the transition from classical to quantum mechanics is an example of a Kuhnian scientific revolution, in which there is a shift from the simple, intuitive, straightforward classical paradigm, to the quantum, convoluted, counterintuitive, amazing new quantum paradigm. In this paper, after having clarified what these quantum paradigms are supposed to be, I analyze whether they constitute a radical departure from the classical paradigm. Contrary to what is commonly maintained, I argue that, in addition to radical (...) quantum paradigms, there are also legitimate ways of understanding the quantum world that do not require any substantial change to the classical paradigm. (shrink)

Niels Bohr was born on October 7, 1885. He was one of the great innovators in physical science in the twentieth century. It so happens that 1985 also marks fifty years since the long discussions, which had begun in the 1920s between Albert Einstein and Bohr on the philosophical problems of quantum physics, attained their apogee. An article co-authored by Einstein, B. Podolsky, and N. Rosen, "Can Quantum Mechanics Be Considered a Complete Description of Physical Reality?," was published in 1935 (...) in the journal Physical Review. According to Bohr, "by virtue of its clarity and, it would seem, flawless argumentation, the work of Einstein, Podolsky, and Rosen has created excitement among physicists and played a great role in the discussion of general philosophical questions of physics." Precisely as a result of the publication of this article, the critical position of Einstein concerning quantum mechanics became known to a broader circle of physicists. In the same year, Bohr responded to Einstein and his co-authors with an article under the same title. (shrink)

Apresentamos os conceitos de inércia, espaço e tempo na mecânica newtoniana. Analisamos o princípio de Mach, segundo o qual a inércia de qualquer corpo é devida a sua interação com os corpos distantes do universo. Em seguida explicamos porque, em geral, a teoria da gravitação de Einstein não implementa este princípio. Discutimos então o trabalho de Erwin Schrödinger que apresenta uma formulação alternativa para a mecânica baseada numa lei de Weber para a gravitação e que é compatível com as idéias (...) de Mach. (shrink)

The 1927 Solvay conference was perhaps the most important meeting in the history of quantum theory. Contrary to popular belief, the interpretation of quantum theory was not settled at this conference, and no consensus was reached. Instead, a range of sharply conflicting views were presented and extensively discussed, including de Broglie's pilot-wave theory, Born and Heisenberg's quantum mechanics, and Schrödinger's wave mechanics. Today, there is no longer an established or dominant interpretation of quantum theory, so it is important to re-evaluate (...) the historical sources and keep the interpretation debate open. This book contains a complete translation of the original proceedings, with background essays on the three main interpretations of quantum theory presented at the conference, and an extensive analysis of the lectures and discussions in the light of current research in the foundations of quantum theory. The proceedings contain much unexpected material, including extensive discussions of de Broglie's pilot-wave theory (which de Broglie presented for a many-body system), and a theory of 'quantum mechanics' apparently lacking in wave function collapse or fundamental time evolution. This book will be of interest to graduate students and researchers in physics and in the history and philosophy of quantum theory. (shrink)

In this paper, we discuss various aspects of Heisenberg’s thought on hidden variables in the period 1927–1935. We also compare Heisenberg’s approach to others current at the time, specifically that embodied by von Neumann’s impossibility proof, but also views expressed mainly in correspondence by Pauli and by Schroedinger. We shall base ourselves mostly on published and unpublished materials that are known but little-studied, among others Heisenberg’s own draft response to the EPR paper. Our aim will be not only to clarify (...) Heisenberg’s thought on the hidden-variables question, but in part also to clarify how this question was understood more generally at the time. (shrink)

The principal results of Schrödinger's paper are reviewed and a possible extension of his formalism for diffusion processes to general quantum mechanical processes is given. The formalism is not in accord with the general theory of transformation of quantum mechanics and violates the basic assumption of the unpredictable change of a system due to a measurement. Nevertheless, the formalism leads to a density operator which is constructed according to accepted quantum mechanical rules.

George Birtwistle (1877–1929) published The New Quantum Mechanics in 1928. His stated aim was to give a detailed account of work which had brought the relatively new subject of quantum mechanics to the fore in the previous few years. The earlier chapters give a restatement of Alfred Landé's theory of multiplets which reconciles it with the new mechanics which follow. Later chapters present the matrix theory of Heisenberg, the q-number theory of Dirac and the wave mechanics of Schroedinger, and synthesise (...) new theories, statistics and controversies in the work of de Broglie, Bose, Einstein, Fermi and Dirac. The book gives a complete overview of the state of quantum mechanics at the end of the second decade of the twentieth century, making it a valuable benchmark for historians of science and mathematicians alike. (shrink)

This second part of a two-part essay discusses recent developments in the Brussels-Austin Group after the mid 1980s. The fundamental concerns are the same as in their similarity transformation approach (see Part I), but the contemporary approach utilizes rigged Hilbert space (whereas the older approach used Hilbert space). While the emphasis on nonequilibrium statistical mechanics remains the same, the use of similarity transformations shifts to the background. In its place arose an interest in the physical features of large Poincaré systems, (...) nonlinear dynamics and the mathematical tools necessary to analyze them. (shrink)

v. 1. Atomic theory and the description of nature -- v. 2. Essays 1932-1957 on atomic physics and human knowledge -- v. 3. Essays 1958-1962 on atomic physics and human knowledge -- v. 4. Causality and complementarity.

Niels Bohr’s “correspondence principle” is typically believed to be the requirement that in the limit of large quantum numbers (n→∞) there is a statistical agreement between the quantum and classical frequencies. A closer reading of Bohr’s writings on the correspondence principle, however, reveals that this interpretation is mistaken. Specifically, Bohr makes the following three puzzling claims: First, he claims that the correspondence principle applies to small quantum numbers as well as large (while the statistical agreement of frequencies is only for (...) large n); second, he claims that the correspondence principle is a law of quantum theory; and third, Bohr argues that formal apparatus of matrix mechanics (the new quantum theory) can be thought of as a precise formulation of the correspondence principle. With further textual evidence, I offer an alternative interpretation of the correspondence principle in terms of what I call Bohr’s selection rule. I conclude by showing how this new interpretation of the correspondence principle readily makes sense of Bohr’s three puzzling claims. (shrink)

: Although Dirac rarely participated in the interpretational debates over quantum theory, it is traditionally assumed that his views were aligned with Heisenberg and Bohr in the so-called Copenhagen-Göttingen camp. However, an unpublished—and apparently unknown—lecture of Dirac's reveals that this view is mistaken; in the famous debate between Einstein and Bohr, Dirac sided with Einstein. Surprisingly, Dirac believed that quantum mechanics was not complete, that the uncertainty principle would not survive in the future physics, and that a deterministic description of (...) the microworld would be recovered. In this paper I show how we can make sense of this unpublished lecture in the context of Dirac's broader philosophy of quantum mechanics, and how our present understanding of Dirac's philosophical views must be revised. (shrink)

Classical mechanics and quantum mechanics are two of the most successful scientific theories ever discovered, and yet how they can describe the same world is far from clear: one theory is deterministic, the other indeterministic; one theory describes a world in which chaos is pervasive, the other a world in which chaos is absent. Focusing on the exciting field of 'quantum chaos', this book reveals that there is a subtle and complex relation between classical and quantum mechanics. It challenges the (...) received view that classical and quantum mechanics are incommensurable, and revives another, largely forgotten tradition due to Niels Bohr and Paul Dirac. By artfully weaving together considerations from the history of science, philosophy of science, and contemporary physics, this book offers a new way of thinking about intertheory relations and scientific explanation. It will be of particular interest to historians and philosophers of science, philosophically-inclined physicists, and interested non-specialists. (shrink)

This paper describes a long-standing, though little-known, debate between Paul Dirac and Werner Heisenberg over the nature of scientific methodology, theory change, and intertheoretic relations. Following Heisenberg’s terminology, their disagreements can be summarized as a debate over whether the classical and quantum theories are “open” or “closed.” A close examination of this debate sheds new light on the philosophical views of two of the great founders of quantum theory.

Remarks on Interpretation, Confirmation and Progressiveness of Early Matrix Mechanics. Our note discusses a case study in view of questions of theory-choice. We examine the extent to which the first 'complete, consistent exposition' of matrix mechanics in 1925 can be claimed to be reasonably confirmed, well interpreted and fruitful. Various strategies, by means of deductions and otherwise, by Born, Jordan and Heisenberg to establish these claims are critically assessed. It is shown that the outcome of the Bothe-Geiger experiment does not (...) represent a 'direct' confirmation of the theory. Finally we pose the question of progressiveness and argue for a low over-all 'problem-solving effectiveness'. (shrink)

Proseguendo nella rilettura della fisica iniziata con il volume Una storia della fisica classica, l'autore tenta di tracciare una storia delle teorie della relatività e di quelle quantistiche. -/- Il taglio è quello del precedente volume: cercare di riscoprire le cose così come apparvero all'atto della loro scoperta e presentarle cercando di essere il più fedele possibile ai lavori originali, utilizzando ampie citazioni tratte da questi e mettendone in evidenza le motivazioni e i limiti. -/- Questa via, una via più (...) "storica" che "filosofica", che evita sia gli approcci di tipo formale che le ricostruzioni di fantasia, permette una comprensione più matura del corpo delle varie discipline, consentendo di recepirle in modo non assiomatico, e nella complessità di una costruzione che non si esaurisce nel presente. (shrink)

Just what forms do (or should) our cognitive attitudes towards scientific theories take? The nature of cognitive commitment becomes particularly puzzling when scientists' commitments are) inconsistent. And inconsistencies have often infected our best efforts in science and mathematics. Since there are no models of inconsistent sets of sentences, straightforward semantic accounts fail. And syntactic accounts based on classical logic also collapse, since the closure of any inconsistent set under classical logic includes every sentence. In this essay I present some evidence (...) that there really was a substantial cognitive commitment to OQT, and that some of its characteristics have a simple and straightforward explanation in terms of a model based on a form of paraconsistent logic. (shrink)

Niels Bohr’s model of the hydrogen atom is widely cited as an example of an inconsistent scientific theory because of its reliance on classical electrodynamics together with assumptions about interactions between matter and electromagnetic radiation that could not be reconciled with CED. This view of Bohr’s model is controversial, but we believe a recently proposed approach to reasoning with inconsistent commitments offers a promising formal reading of how Bohr’s model worked. In this paper we present this new way of reasoning (...) with inconsistent commitments and compare it with other approaches before applying it to Bohr’s model and offering some suggestions for how it might be extended to account for subsequent developments in old quantum theory. (shrink)

The standard model of the quantum theory of measurement is based on an interaction Hamiltonian in which the observable to be measured is multiplied by some observable of a probe system. This simple Ansatz has proved extremely fruitful in the development of the foundations of quantum mechanics. While the ensuing type of models has often been argued to be rather artificial, recent advances in quantum optics have demonstrated their principal and practical feasibility. A brief historical review of the standard model (...) together with an outline of its virtues and limitations are presented as an illustration of the mutual inspiration that has always taken place between foundational and experimental research in quantum physics. (shrink)

In a period of over 50 years, Peter Mittelstaedt has made substantial and lasting contributions to several fields in theoretical physics as well as the foundations and philosophy of physics. Here we present an overview of his achievements in physics and its foundations which may serve as a guide to the bibliography (printed in this Festschrift) of his publications. An appraisal of Peter Mittelstaedt’s work in the philosophy of physics is given in a separate contribution by B. Falkenburg.

Arthur S. Eddington, FRS, (1882–1944) was one of the most prominent British scientists of his time. He made major contributions to astrophysics and to the broader understanding of the revolutionary theories of relativity and quantum mechanics. He is famed for his astronomical observations of 1919, confirming Einstein’s prediction of the curving of the paths of starlight, and he was the first major interpreter of Einstein’s physics to the English-speaking world. His 1928 book, The Nature of the Physical World, here re-issued (...) in a critical, annotated edition, was largely responsible for his fame as a public interpreter of science and has had a significant influence on both the public and the philosophical understanding of 20th-century physics. In degree, Eddington’s work has entered into our contemporary understanding of modern physics, and, in consequence, critical attention to his most popular book repays attention. Born at Kendal near Lake Windermere in the northwest of England into a Quaker background, Eddington attended Owens College, Manchester, and afterward Trinity College, Cambridge, where he won high mathematical honors, including Senior Wrangler. He became Plumian Professor of Astronomy at Cambridge in 1913 and in 1914 Director of the Cambridge Observatory. Eddington was a conscientious objector during the First World War. By the end of his career, he was widely esteemed and had received honorary degrees from many universities. He was elected president of the Royal Astronomical Society (1921–1923), and was subsequently elected President of the Physical Society (1930–1932), the Mathematical Association (1932), and the International Astronomical Union (1938–1944). Eddington was knighted in 1930 and received the Order of Merit in 1938. During the 1930s, his popular and more philosophical books made him a well known figure to the general public. Philosophers have found his writings of considerable interest, and have debated his themes for nearly a hundred years. (shrink)