History of Quantum Mechanics

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)

I argue that Immanuel Kant's critical philosophy—in particular the doctrine of transcendental idealism which grounds it—is best understood as an `epistemic' or `metaphilosophical' doctrine. As such it aims to show how one may engage in the natural sciences and in metaphysics under the restriction that certain conditions are imposed on our cognition of objects. Underlying Kant's doctrine, however, is an ontological posit, of a sort, regarding the fundamental nature of our cognition. This posit, sometimes called the `discursivity thesis', while considered (...) to be completely obvious and uncontroversial by some, has nevertheless been denied by thinkers both before and after Kant. One such thinker is Jakob Friedrich Fries, an early neo-Kantian thinker who, despite his rejection of discursivity, also advocated for a metaphilosophical understanding of critical philosophy. As I will explain, a consequence for Fries of the denial of discursivity is a radical reconceptualisation of the method of critical philosophy; whereas this method is a priori for Kant, for Fries it is in general empirical. I discuss these issues in the context of quantum theory, and I focus in particular on the views of the physicist Niels Bohr and the Neo-Friesian philosopher Grete Hermann. I argue that Bohr's understanding of quantum mechanics can be seen as a natural extension of an orthodox Kantian viewpoint in the face of the challenges posed by quantum theory, and I compare this with the extension of Friesian philosophy that is represented by Hermann's view. (shrink)

Sobre las partículas subatómicas y su influencia en el hombre.In Spanish with a briefing in English.

This chapter is about Grete Hermann, a philosopher-mathematician who productively and mutually beneficially interacted with the founders of quantum mechanics in the early period of that theory's elaboration. Hermann was a neo-Kantian philosopher. At the heart of Immanuel Kant's critical philosophy lay the question of the conditions under which we can be said to know something objectively, a question Hermann found to be particularly pressing in quantum mechanics. Hermann's own approach to Neo-Kantianism was Neo-Friesian. Jakob Friedrich Fries, like Kant, had (...) understood critical philosophy to be an essentially epistemic project. Fries departed from Kant in his account of the elements involved in our cognition. In this chapter it is discussed how, beginning from a neo-Friesian understanding of critical philosophy, Hermann is led to conclude that quantum mechanics shows us that physical knowledge is fundamentally split; that the objects of quantum mechanics are only objects from a particular perspective and in the context of a particular physical interaction. It will be seen how Hermann's solution to the problem of objectivity in quantum mechanics is a natural one from a neo-Friesian point of view, even though it disagrees with those offered by more orthodox versions of Kantian doctrine. (shrink)

as the chief novelty in the quantum description of nature, Einstein for having found vindication in 3 relativity theory for either positivism or realism, depending upon whom one asks. Famous as is each in his own domain, they are famous also, together, for their decades-long disagreement over the future of fundamental physics, their respective embrace and rejection of quantum indeterminacy being only the most widely-known point of contention.

Niels Bohr was a central figure in quantum physics, well known for his work on atomic structure and his contributions to the Copenhagen interpretation of quantum mechanics. In this book, philosopher of science Slobodan Perović explores the way Bohr practiced and understood physics, and analyzes its implications for our understanding of modern science. Perović develops a novel approach to Bohr’s understanding of physics and his method of inquiry, presenting an exploratory symbiosis of historical and philosophical analysis that uncovers the key (...) aspects of Bohr’s philosophical vision of physics within a given historical context. -/- To better understand the methods that produced Bohr’s breakthrough results in quantum phenomena, Perović clarifies the nature of Bohr’s engagement with the experimental side of physics and lays out the basic distinctions and concepts that characterize his approach. Rich and insightful, Perović’s take on the early history of quantum mechanics and its methodological ramifications sheds vital new light on one of the key figures of modern physics. (shrink)

The paper offers an argument against an intuitive reading of the Stone-von Neumann theorem as a categoricity result, thereby pointing out that this theorem does not entail any model-theoretical difference between the theories that validate it and those that don't.

Scientific realism is the view that our best scientific theories can be regarded as (approximately) true. This is connected with the view that science, physics in particular, and metaphysics could (and should) inform one another: on the one hand, science tells us what the world is like, and on the other hand, metaphysical principles allow us to select between the various possible theories which are underdetermined by the data. Nonetheless, quantum mechanics has always been regarded as, at best, puzzling, if (...) not contradictory. As such, it has been considered for a long time at odds with scientific realism, and thus a naturalized quantum metaphysics was deemed impossible. Luckily, now we have many quantum theories compatible with a realist interpretation. However, scientific realists assumed that the wave-function, regarded as the principal ingredient of quantum theories, had to represent a physical entity, and because of this they struggled with quantum superpositions. In this paper I discuss a particular approach which makes quantum mechanics compatible with scientific realism without doing that. In this approach, the wave-function does not represent matter which is instead represented by some spatio-temporal entity dubbed the primitive ontology: point-particles, continuous matter fields, space-time events. I argue how within this framework one develops a distinctive theory-construction schema, which allows to perform a more informed theory evaluation by analyzing the various ingredients of the approach and their inter-relations. (shrink)

Building on self-professed perspectival approaches to both scientific knowledge and causation, I explore the potentially radical suggestion that perspectivalism can be extended to account for a type of objectivity in science. Motivated by recent claims from quantum foundations that quantum mechanics must admit the possibility of observer-dependent facts, I develop the notion of ‘perspectival objectivity’, and suggest that an easier pill to swallow, philosophically speaking, than observer-dependency is perspective-dependency, allowing for a notion of observer-independence indexed to an agent perspective. Working (...) through the case studies of colour perception and causal perspectivalism, I identify two places within which I claim perspectival objectivity is already employed, and make the connection to quantum mechanics through Bohr’s philosophy of quantum theory. I contend that perspectival objectivity can ensure, despite the possibility of perspective-dependent scientific facts, the objectivity of scientific inquiry. (shrink)

A recent series of experiments have demonstrated that a classical fluid mechanical system, constituted by an oil droplet bouncing on a vibrating fluid surface, can be induced to display a number of behaviours previously considered to be distinctly quantum. To explain this correspondence it has been suggested that the fluid mechanical system provides a single-particle classical model of de Broglie’s idiosyncratic ‘double solution’ pilot wave theory of quantum mechanics. In this paper we assess the epistemic function of the bouncing oil (...) droplet experiments in relation to quantum mechanics. We find that the bouncing oil droplets are best conceived as an analogue illustration of quantum phenomena, rather than an analogue simulation, and, furthermore, that their epistemic value should be understood in terms of how-possibly explanation, rather than confirmation. Analogue illustration, unlike analogue simulation, is not a form of ‘material surrogacy’, in which source empirical phenomena in a system of one kind can be understood as ‘standing in for’ target phenomena in a system of another kind. Rather, analogue illustration leverages a correspondence between certain empirical phenomena displayed by a source system and aspects of the ontology of a target system. On the one hand, this limits the potential inferential power of analogue illustrations, but, on the other, it widens their potential inferential scope. In particular, through analogue illustration we can learn, in the sense of gaining how-possibly understanding, about the putative ontology of a target system via an experiment. As such, the potential scientific value of these extraordinary experiments is undoubtedly a significant one. (shrink)

In 1935/1936 Kurt Gödel wrote three notebooks on the foundations of quantum mechanics, which have now been entirely transcribed for the first time. Whereas a lot of the material is rather technical in character, many of Gödel's remarks have a philosophical background and concentrate on Leibnizian monadology as well as on vitalism. Obviously influenced by the vitalistic writings of Hans Driesch and his ‘proofs’ for the existence of an entelechy in every living organism, Gödel briefly develops the idea of a (...) computing machine which closely resembles Turing's groundbreaking conception. After introducing the notebooks on quantum mechanics, this article describes Gödel's vitalistic Weltbild and the ideas leading to the development of his computing machine. It investigates a notion of lawlike sequence which closely resembles Turing's concept of a computable number and which Gödel himself calls ‘problematic’, and compares it to the opposed concept of randomness, drawing upon the notion of program-size complexity. Finally, Gödel's machine is implemented in a dialect of the Lisp programing language. (shrink)

GianCarlo Ghirardi passed away on June 1st, 201. He would have turned 83 on October 28, 2018. He was without any doubt one of the most prominent theoretical physicists working on the foundation and the philosophy of quantum mechanics. In this paper I review some of his achievements and underline how his research influenced the philosophy of physics community.

I look at the distinction between between realist and antirealist views of the quantum state. I argue that this binary classification should be reconceived as a continuum of different views about which properties of the quantum state are representationally significant. What's more, the extreme cases -- all or none --- are simply absurd, and should be rejected by all parties. In other words, no sane person should advocate extreme realism or antirealism about the quantum state. And if we focus on (...) the reasonable views, it's no longer clear who counts as a realist, and who counts as an antirealist. Among those taking a more reasonable intermediate view, we find figures such as Bohr and Carnap -- in stark opposition to the stories we've been told. (shrink)

Die vorliegende Veröffentlichung stellt eine Würdigung der Naturphilosophie und Erkenntnistheorie der Philosophin Grete Henry-Hermann dar. Die Schülerin der Mathematikerin Emmy Noether und des Philosophen Leonard Nelson gehört zu den frühen Interpret(inn)en der Quantenmechanik. Werner Heisenberg setzte ihr in seinem Buch „Der Teil und das Ganze“ ein Denkmal. Erstmals sind in einem Band ihre naturphilosophischen und erkenntnistheoretischen Schriften zusammengefasst. Eine umfangreiche Einleitung verschiedener Autoren führt in das Werk von Grete Henry-Hermann ein. Ergänzt wird diese Ausgabe durch Auszüge aus der Korrespondenz über (...) naturphilosophische und erkenntnistheoretische Themen, darunter auch ein Briefwechsel mit Carl Friedrich von Weizsäcker, Werner Heisenberg und Gustav Heckmann. -/- Der Inhalt ● Grete Henry-Hermanns Beitrag zur Interpretation Quantenmechanik ● Grete Henry-Hermanns Arbeiten zum Verhältnis von moderner Physik und Transzendentalphilosophie ● Die Dissertation von Grete Hermann: Die Frage der endlich vielen Schritte in der Theorie der Polynomideale (1925) ● Erörterungen zur Frage der Willensfreiheit und zur Bedeutung der Verhaltensforschung für die Kritik der Vernunft ● Auszüge aus dem Briefwechsel aus den Jahren 1925 bis 1982 -/- Der Herausgeber Privatdozent Dr. phil. Dipl.-Phys. Kay Herrmann lehrt Wissenschaftstheorie an der Technischen Universität Chemnitz -/- . (shrink)

I propose a rational reconstruction of the early quantum theory in terms of the ideas presented by Ernst Cassirer. Specifically, I propose to reconsider the early quantum theory through the lens of the method of conceptual functionalization that Ernst Cassirer laid down in his Substance and Function and he later refined in Determinism and Indeterminism in Modern Physics. Following Cassirer’s functional interpretation of natural sciences, it is my primary concern to reconsider the conceptual evolution of Planck’s quantum of action from (...) 1900 to 1913. In this regard, I shall emphasize the importance of the quantum of action in the architectonic structure of the early quantum theory, in the role of an element of fundamental continuity between the first quantum theory and the formulation by Niels Bohr of the first atomic theory. (shrink)

After a brief review of the golden ratio in history and our previous exposition of the fine-structure constant and equations with the exponential function, the fine-structure constant is studied in the context of other research calculating the fine-structure constant from the golden ratio geometry of the hydrogen atom. This research is extended and the fine-structure constant is then calculated in powers of the golden ratio to an accuracy consistent with the most recent publications. The mathematical constants associated with the golden (...) ratio are also involved in both the calculation of the fine-structure constant and the proton-electron mass ratio. These constants are included in symbolic geometry of historical relevance in the science of the ancients. (shrink)

This paper considers Weylean invariantism, i.e., the view that objectivity requires categoricity, and argues that since the Stone-von Neumann theorem can be naturally interpreted as a categoricity result, the view is falsified by quantum field theory.

Niels Bohr and Philosophy of Physics: Twenty-First Century Perspectives examines the work, influences and legacy of the Nobel Prize physicist and philosopher of experiment Niels Bohr. While covering Bohr's groundbreaking contribution to quantum mechanics, this collection reveals the philosophers who influenced his work. Linking him to the pragmatist C.I. Lewis and the Danish philosopher Harald Høffding, it draws strong similarities between Bohr's philosophy and the Kantian way of thinking. Addressing the importance of Bohr's views of classical concepts, it discusses how (...) his interpretation of quantum mechanics now compares with a variety of issues that have arisen only since his lifetime, including decoherence and other non-collapse arguments. Balancing historical themes with contemporary ideas, Niels Bohrs and Philosophy of Physics reveals Bohr's on-going contribution to the philosophy of science and confirms his place in the history of philosophy. (shrink)

Although written in Japanese, an overall picture of quantum physics is drawn, which would surely be useful for beginners as well as researchers of the humanities.

What are quantum entities? Is the quantum domain deterministic or probabilistic? Orthodox quantum theory (OQT) fails to answer these two fundamental questions. As a result of failing to answer the first question, OQT is very seriously defective: it is imprecise, ambiguous, ad hoc, non-explanatory, inapplicable to the early universe, inapplicable to the cosmos as a whole, and such that it is inherently incapable of being unified with general relativity. It is argued that probabilism provides a very natural solution to the (...) quantum wave/particle dilemma and promises to lead to a fully micro-realistic, testable version of quantum theory that is free of the defects of OQT. It is suggested that inelastic interactions may induce quantum probabilistic transitions. (shrink)

From the exponential function of Euler’s equation to the geometry of a fundamental form, a calculation of the fine-structure constant and its relationship to the proton-electron mass ratio is given. Equations are found for the fundamental constants of the four forces of nature: electromagnetism, the weak force, the strong force and the force of gravitation. Symmetry principles are then associated with traditional physical measures.

Grete Hermann was a pupil of mathematical physicist Emmy Noether, follower and co-worker of neo-Kantian philosopher Leonard Nelson, and an important intellectual figure in post-war German social democracy. She is best known for her work on the philosophy of modern physics in the 1930s, some of which emerged from intense discussions with Heisenberg and Weizsäcker in Leipzig. Hermann’s aim was to counter the threat to the Kantian notion of causality coming from quantum mechanics. She also discussed in depth the question (...) of ‘hidden variables’ and provided an extensive analysis of Bohr’s notion of complementarity. This volume includes translations of Hermann’s two most important essays on this topic: one hitherto unpublished and one translated here into English for the first time. It also brings together recent scholarly contributions by historians and philosophers of science, physicists, and philosophers and educators following in Hermann’s steps. Hermann's work places her in the first rank among philosophers who wrote about modern physics in the first half of the last century. Those interested in the many fields to which she contributed will find here a comprehensive discussion of her philosophy of physics that places it in the context of her wider work. (shrink)

The notion of equality between two observables will play many important roles in foundations of quantum theory. However, the standard probabilistic interpretation based on the conventional Born formula does not give the probability of equality between two arbitrary observables, since the Born formula gives the probability distribution only for a commuting family of observables. In this paper, quantum set theory developed by Takeuti and the present author is used to systematically extend the standard probabilistic interpretation of quantum theory to define (...) the probability of equality between two arbitrary observables in an arbitrary state. We apply this new interpretation to quantum measurement theory, and establish a logical basis for the difference between simultaneous measurability and simultaneous determinateness. (shrink)

It is well known that Niels Bohr insisted on the necessity of classical concepts in the account of quantum phenomena. But there is little consensus concerning his reasons, and what he exactly meant by this. In this paper, I re-examine Bohr’s interpretation of quantum mechanics, and argue that the necessity of the classical can be seen as part of his response to the measurement problem. More generally, I attempt to clarify Bohr’s view on the classical/quantum divide, arguing that the relation (...) between the two theories is that of mutual dependence. An important element in this clarification consists in distinguishing Bohr’s idea of the wave function as symbolic from both a purely epistemic and an ontological interpretation. Together with new evidence concerning Bohr’s conception of the wave function collapse, this sets his interpretation apart from both standard versions of the Copenhagen interpretation, and from some of the reconstructions of his view found in the literature. I conclude with a few remarks on how Bohr’s ideas make much sense also when modern developments in quantum gravity and early universe cosmology are taken into account. (shrink)

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’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 huge success of quantum mechanics as a predictive theory has been accompanied, from the very beginning, by doubts and controversy about its foundations and interpretation. This book looks in detail at how research on foundations evolved after WWII, when it was revived, until the mid 1990s, when most of this research merged into the technological promise of quantum information. It is the story of the quantum dissidents, the scientists who brought this subject from the margins of physics into its (...) mainstream. It is also a history of concepts, experiments, and techniques, and of the relationships between physics and the world at large, touching on themes such as the Cold War, McCarthyism, Zhdanovism, and the unrest of the late 1960s. (shrink)

In popular culture, Einstein’s shaggy mustaches and disheveled hairstyle have come to represent the image of physics itself. The most famous physicist of the twentieth century is mainly celebrated as the creator of relativity, intended as both special and general relativity theories. The ubiquitous E = mc2 equation comes hand in hand with pictures of Einstein’s thoughtful wrinkles. Insofar as quantum theory is concerned, Einstein is usually remembered as a strenuous opponent of quantum mechanics who rejected this successful theory on (...) epistemological grounds till the end of his life.In Einstein and the Quantum: The Quest of the Valiant Swabian Douglas Stone—a theoretical physicist specialized in the application of quantum mechanics to solid-state physics—pursues the clearly stated aim of challenging this conventional view. In fact, Einstein made momentous contributions to the quantum theory as the main proponent of novel notions that radically shook the foundat .. (shrink)

An introduction is given to the geometry and harmonics of the Golden Apex in the Great Pyramid, with the metaphysical and mathematical determination of the fine-structure constant of electromagnetic interactions. Newton's gravitational constant is also presented in harmonic form and other fundamental physical constants are then found related to the quintessential geometry of the Golden Apex in the Great Pyramid.

During World War II, Niels Bohr realized that the nature of war had changed irrevocably due to the introduction of the atomic bomb. This, in his opinion, meant that nation states had to be open about nuclear knowledge and negotiate toward peace. The bomb presented a threat, yet at the same time, an opportunity, as Bohr would argue in his characteristic way. It is not too difficult to point to the epistemological origin of Bohr’s argument: One easily identifies resonances with (...) his ideas on “complementarity” from quantum mechanics. According to Bohr’s doctrine of complementarity, a quantum mechanical object shows certain qualities depending on the experimental perspective from which it is studied; and these qualities may be mutually exclusive. However, they should in fact be looked upon as “complementary” properties that together make up the full picture of the object under investigation.Initially, Bohr could express his ideas to the highest circles of power. This would soon change, howe .. (shrink)

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)

The aim of the famous Born and Jordan 1925 paper was to put Heisenberg’s matrix mechanics on a firm mathematical basis. Born and Jordan showed that if one wants to ensure energy conservation in Heisenberg’s theory it is necessary and sufficient to quantize observables following a certain ordering rule. One apparently unnoticed consequence of this fact is that Schrödinger’s wave mechanics cannot be equivalent to Heisenberg’s more physically motivated matrix mechanics unless its observables are quantized using this rule, and not (...) the more symmetric prescription proposed by Weyl in 1926, which has become the standard procedure in quantum mechanics. This observation confirms the superiority of Born–Jordan quantization, as already suggested by Kauffmann. We also show how to explicitly determine the Born–Jordan quantization of arbitrary classical variables, and discuss the conceptual advantages in using this quantization scheme. We finally suggest that it might be possible to determine the correct quantization scheme by using the results of weak measurement experiments. (shrink)

Teaching quantum theory is a legendary difficult task, not only due to its weirdness, but also because it is philosophically sensitive. Examples from the history and philosophy of science show that one of the main challenges is to find a balanced approach between introducing the most basic quantum concepts while taking into account interpretational issues. Although there is no privileged interpretation for QT, teaching and research about QT must make the interpretational choice used explicit. In addition any introductory course should (...) emphasize the strictly quantum features in order to prevent students from establishing undesirable links with classical concepts. While teaching focused on the mathematical formalism remains a choice, pictures may be exploited, but in this case complementarity should be explicitly and carefully introduced. Finally, we argue that the teaching of QT, maybe more than other areas in physics, must be informed by the history and philosophy of science. (shrink)

The Correspondence Principle of old quantum theory is commonly considered to be the requirement that quantum and classical theories converge in their empirical predictions in the appropriate asymptotic limit. That perception has persisted despite the fact that Bohr and other early proponents of CP clearly did not intend it as a mere requirement, and despite much recent historical work. In this paper, I build on this work by first giving an explicit formulation to the mentioned asymptotic requirement ) and then (...) discussing various possible formulations of CP for emission on the basis of the primary literature as well as general physical and metaphysical considerations. I shall then show that, in all of the most probable interpretations of CP that consider quantum theory as a universal theory, any system incorporating both CR and CP for emission would in fact be inconsistent. Old quantum theory measurably contradicts classical physics in the classical regime. (shrink)

Despite a flurry of renewed scholarly interest in the development of Heisenberg’s scientific work, and in his complex relation to the dramatic unfolding of German cultural history in his time, there has yet to be executed a sustained and philosophically critical interpretative commentary on the book that is his crucial philosophical-ontological legacy, Physics and Philosophy: The Revolution in Modern Science. Given the profound ontological puzzles that continue to attend quantum physics and its implications for humanity’s past as well as present (...) and future conception of reality, such a critical exegesis of this text is overdue. No thinker has yet appeared who possesses such an authoritative combination of the decisively necessary learning, in quantum physics and in the historical development of philosophic ontology. This article tries to extricate the central nerve of Heisenberg’s sinuously unfolding, dialectical exposition, and in the process to elucidate its strengths but also its deep ambiguities and perplexities—which express fundamental dilemmas that pervade contemporary ontology. (shrink)

This paper compares Cassirer´s and Bohr´s views on symbolic knowledge in quantum physics. Although both of them consider quantum physics as symbolic knowledge, for Cassirer this amounts to a complete renunciation to intuition in quantum physics, while according to Bohr only spatio-temporal images may provide the mathematical formalism of the theory with physical reference. We show the Kantian roots of Bohr´s position and we claim that his Kantian concept of symbol enables Bohr to account for the sensible content of quantum (...) theory as well as for its systematic relation to classical physics. (shrink)

El principio de correspondencia y el punto de vista de la complementariedad constituyen los sucesivos ejes alrededor de los cuales gira la interpretación de Bohr de la teoría cuántica. En este trabajo sostenemos que el concepto kantiano de analogía resulta un hilo conductor que permite comprender satisfactoriamente tal desarrollo histórico del pensamiento de Bohr. Mostraremos que el principio de correspondencia guía la búsqueda de analogías en la experiencia, mientras que desde el punto de vista de la complementariedad Bohr establece analogías (...) simbólicas. The principle of correspondence and, later, the viewpoint of complementarity are the axes around which Bohr´s interpretation of quantum theory rotates. In this paper we claim that the Kantian notion of analogy enables a satisfactory understanding of such historical development of Bohr's thought. We shall show that the principle of correspondence guides the search for analogies in experience, while from the viewpoint of complementarity Bohr establishes symbolic analogies. (shrink)

The notion of uncertainty in the description of a physical system has assumed prodigious importance in the development of quantum theory. Overcoming the early misunderstanding and confusion, the concept grew continuously and still remains an active and fertile research field. Curious new insights and correlations are gained and developed in the process with the introduction of new ‘measures’ of uncertainty or indeterminacy and the development of quantum measurement theory. In this article we intend to reach a fairly uptodate status report (...) of this yet unfurling concept and its interrelation with some distinctive quantum features like nonlocality, steering and entanglement/inseparability. Some recent controversies are discussed and the grey areas are mentioned. (shrink)

Arnold Sommerfeld introduced the fine-structure constant that determines the strength of the electromagnetic interaction. Following Sommerfeld, Wolfgang Pauli left several clues to calculating the fine-structure constant with his research on Johannes Kepler's view of nature and Pythagorean geometry. The Laplace limit of Kepler's equation in classical mechanics, the Bohr-Sommerfeld model of the hydrogen atom and Julian Schwinger's research enable a calculation of the electron magnetic moment anomaly. Considerations of fundamental lengths such as the charge radius of the proton and mass (...) ratios suggest some further foundational interpretations of quantum electrodynamics. (shrink)

Werner Heisenberg's 1925 paper ‘Quantum-theoretical re-interpretation of kinematic and mechanical relations’ marks the beginning of quantum mechanics. Heisenberg famously claims that the paper is based on the idea that the new quantum mechanics should be ‘founded exclusively upon relationships between quantities which in principle are observable’. My paper is an attempt to understand this observability principle, and to see whether its employment is philosophically defensible. Against interpretations of ‘observability’ along empiricist or positivist lines I argue that such readings are philosophically (...) unsatisfying. Moreover, a careful comparison of Heisenberg's reinterpretation of classical kinematics with Einstein's argument against absolute simultaneity reveals that the positivist reading does not fit with Heisenberg's strategy in the paper. Instead the appeal to observability should be understood as a specific criticism of the causal inefficacy of orbital electron motion in Bohr's atomic model. I conclude that the tacit philosophical principle behind Heisenberg's argument is not a positivistic connection between observability and meaning, but the idea that a theory should not contain causally idle wheels. (shrink)

This paper addresses arguments that “separability” is an assumption of Bell’s theorem, and that abandoning this assumption in our interpretation of quantum mechanics (a position sometimes referred to as “holism”) will allow us to restore a satisfying locality principle. Separability here means that all events associated to the union of some set of disjoint regions are combinations of events associated to each region taken separately.In this article, it is shown that: (a) localised events can be consistently defined without implying separability; (...) (b) the definition of Bell’s locality condition does not rely on separability in any way; (c) the proof of Bell’s theorem does not use separability as an assumption. If, inspired by considerations of non-separability, the assumptions of Bell’s theorem are weakened, what remains no longer embodies the locality principle. Teller’s argument for “relational holism” and Howard’s arguments concerning separability are criticised in the light of these results. Howard’s claim that Einstein grounded his arguments on the incompleteness of QM with a separability assumption is also challenged. Instead, Einstein is better interpreted as referring merely to the existence of localised events. Finally, it is argued that Bell rejected the idea that separability is an assumption of his theorem. (shrink)

Summary The emergence of quantum theory in the early decades of the twentieth century was accompanied by a wide range of popular science books, all of which presented in words, and a few in images, new scientific ideas about the structure of the atom. The work of physicists such as Ernest Rutherford and Niels Bohr, among others, was pivotal to the so-called planetary model of the atom, which, still today, is used in popular accounts and in science textbooks. In an (...) attempt to add to our knowledge about the popular trajectory of the new atomic physics, this paper examines one book in particular, co-authored by Danish science writer Helge Holst and Dutch physicist and close collaborator of Niels Bohr, Hendrik A. Kramers. Translated from Danish into four European languages, the book not only explained contemporary ideas about the quantum atom, but also discussed unresolved problems. Moreover, the book was quite explicit in identifying the quantum atom with the atom as described by Bohr's theory. We argue that Kramers and Holst's book, along with other ?atomic books?, was a useful tool for physicists and science popularisers in trying to understand the new quantum physics. (shrink)