Popper: Philosophy of Physics

Karl Popper and Paul Feyerabend were among the most influential philosophers of science of the twentieth century. Extensive studies have been dedicated to the development of their controversial rel...

Durant toute sa vie intellectuelle, Karl Popper a accusé Niels Bohr d’avoir défendu des thèses subjectivistes à propos de la mécanique quantique et d’avoir introduit le concept de sujet au sein de la physique. Or, cette accusation va à l’encontre des textes de Bohr. L’objectif de cet article est de montrer que, dans sa restitution même des positions de Bohr, Popper n’a pas pris au sérieux une thèse centrale défendue par Bohr, qu’on appelle « la contextualité des phénomènes quantiques», et (...) qui a pour conséquence de modifier en profondeur l’acte de mesure et la constitution de l’objet en mécanique quantique. Nous essayons de montrer que c’est cette difficulté dans la restitution des positions de Bohr qui l’a amené à porter son accusation de subjectivisme à l’encontre de Bohr. (shrink)

While Karl Popper’s philosophy of science has only few followers among modern philosophers, it is easily the view of science with the biggest impact on practicing scientists. According to Peter Medawar, Nobel laureate and eminent physiologist, Popper was the greatest authority ever on the scientific method. He praised the “great strength of Karl Popper’s conception of the scientific process,” a main reason for the praise being “that it is realistic—it gives a pretty fair picture of what goes on in real (...) life laboratories” (Medawar 1990, p. 100). Either explicitly or (more often) implicitly, many scientists subscribe to some version of simplified Popperianism, usually by adopting the demarcation criterion that a .. (shrink)

On the basis of the Suppes–Sneed structuralview of scientific theories, we take a freshlook at the concept of refutability,which was famously proposed by K.R. Popper in 1934 as a criterion for the demarcation of scientific theories from non-scientific ones, e.g., pseudo-scientificand metaphysical theories. By way of an introduction we argue that a clash between Popper and his critics on whether scientific theories are, in fact, refutablecan be partly explained by the fact Popper and his criticsascribed different meanings to the term (...) theoryThen we narrow our attention to one particular theory,namely quantum mechanics, in order to elucidate general matters discussed. We prove that quantum mechanics is irrefutable in a rather straightforward sense, but argue that it is refutable in a more sophisticated sense, which incorporates someobservations obtained by looking closely at the practiceof physics. We shall locate exactly where non-rigourous elements enter the evaluation of a scientific theory – thismakes us see clearly how fruitful mathematics isfor the philosophy of science. (shrink)

In his 1939 Lectures, the prominent Soviet physicist L. I. Mandelstam proposed an interpretation of quantum mechanics that was understood in different ways. To assess Mandelstam's interpretation, we classify contemporary interpretations of quantum mechanics and compare his interpretation with others developed in the 1930s. We conclude that Mandelstam's interpretation belongs to the family of minimal statistical interpretations and has much in common with interpretations developed by American physicists. Mandelstam's characteristic message was his theory of indirect measurement, which influenced his discussion (...) of the "reduction of the wave packet" and the Einstein, Podolsky, and Rosen argument. This article also reconstructs what lay behind Mandelstam's interpretation of quantum mechanics. This was his operationalism, by virtue of which his interpretation resembled Kemble's, in which the statistical and Copenhagen views had been combined. Like Popper and Margenau, Mandelstam followed R. von Mises's empirical conception of probability. Mandelstam, like the other proponents of the statistical approach to quantum mechanics, was affected by the culture of macroscopic experimentation with its emphasis on statistical measurement. (shrink)

Recently, there has been increasing theoretical and experimental interest in Popper's gedanken experiment. We calculate in this paper, using the path integral approach, the diffraction patterns predicted by quantum mechanics for this arrangement. The calculations confirm the narrowing of the width of the pattern in absence of the slit obtained experimentally by Kim and Shih (Y. Kim and Y. Shih, Found. Phys. 29, 1849 (1999)).

Popper conceived an experiment whose analysis led to a result that he deemed absurd. Popper wrote that his reasoning was based on the Copenhagen interpretation and therefore invalidated it. Many authors who have examined Popper's analysis have found in it various technical flaws which are briefly summarized here. However, the aim of the present article is not technical. My concern is to redress logical flaws in Popper's argument: the terminology he uses is ambiguous, his analysis involves counterfactual hypotheses, and it (...) violates Bohr's complementarity principle. Therefore, the absurdity of Popper's result only confirms Bohr's approach. (shrink)

An entangled pair of photons (1 and 2) are emitted in opposite directions. A narrow slit is placed in the path of photon 1 to provide the precise knowledge of its position on the y-axis and this also determines the precise y-position of its twin, photon 2, due to quantum entanglement. Is photon 2 going to experience a greater uncertainty in momentum, that is, a greater Δpy because of the precise knowledge of its position y? The experimental data show Δy (...) Δ py < h for photon 2. Can this recent realization of the thought experiment of Karl Popper signal a violation of the uncertainty principle? (shrink)

There is no doubt at all that the issue of determinism versus indeterminism was a central, dominating theme of Popper's thought. By his own account he saw his criticism of the thesis of determinism as crucial to his defence not only of the reality of human freedom, moral responsibility and creativity but also as equally fundamental to his account of human rationality and to his theory of the content and growth of science as an objective, rational and most importantly demonstrably (...) rational enterprise. Consequently a great deal of his writings discussing both the content and methodology of the natural and the social sciences alternately bear upon and presuppose his defence of indeterminism. (shrink)

Sir K. R. Popper's experimental schemes challenge the Copenhagen interpretation of quantum theory, principally Heisenberg's indeterminacy relations and the EPR paradox. “The so-called Einstein-Podolsky-Rosen paradox is not a paradox. It is a theoretical statement in expectation of an interpretation,” says K. R. Popper in this interview. “My experiment ought to be a classical experiment. It is very simple and free from any additional assumption. It should really be done.”.

In the first part of this work(1) we have explicated the spacetime structure of the probabilistic organization of quantum mechanics. We have shown that each quantum mechanical state, in consequence of the spacetime characteristics of the epistemic operations by which the observer produces the state to be studied and the processes of qualification of these, brings in a tree-like spacetime structure, a “quantum mechanical probability tree,” thattransgresses the theory of probabilities as it now stands. In this second part we develop (...) the general implications of these results.Starting from the lowest level of cognitive action and creating an appropriate symbolism, we construct a “relativizing epistemic syntax,” a “general method of relativized conceptualization” where—systematically—each description is explicitly referred to the epistemic operations by which the observer produces the entity to be described and obtains qualifications of it. The method generates a typology of increasingly complex relativized descriptions where the question of realism admits of a particularly clear pronouncement. Inside this typology the epistemic processes that lie—UNIVERSALLY—at thebasis ofany conceptualization, reveal a tree-like spacetime structure. It appears in particular that the spacetime structure of the relativized representation of aprobabilistic description, which transgresses the nowadays theory of probabilities,is the general mould of which the quantum mechanical probability trees are only particular realizations. This entails a clear definition of the descriptional status of quantum mechanics. While the recognition of theuniversal cognitive content of the quantum mechanical formalism opens up vistas towardmathematical developments of the relativizing epistemic syntax.The relativized representation of a probabilistic description leads with inner necessity to a “morphic” interpretation of probabilities thatcan be regarded as a formalized and deepening elaboration of Sir Karl Popper's “propensity” interpretation. A functional is then constructed, the “opacity functional,” that associatesa mathematical expression to the Popperian “propensities”. Furthermore the opacity functional produces adeductive definition of Shannon's “informational entropy.” Thereby there appears an explicitly unified relativized probabilistic-informational approach. This sketches out a second branch of a future mathematical epistemic syntax, to be connected with the branch stemming from quantum mechanics.The problem of the objectivity of probabilistic descriptions acquires certain precise rephrasings and—in a sense—solution. (shrink)

The eminent mathematical physicist Sir Hermann Bondi once said: “There is no more to science than its method, and there is no more to its method than Popper has said.” Indeed, many regard Sir Karl Raimund Popper the greatest philosopher of science in our generation. Much of what Popper “has said” refers to physics, but physicists, generally speaking, have little knowledge of what he has said. True, Popper's philosophy of science and, in particular, his realistic interpretation of quantum mechanics deviates (...) considerably from the generally accepted doctrine. But as Popper, rightly I think, points out, it is precisely the proliferation of divergent theories which promotes the growth of scientific knowledge; it would be a danger for physics if physicists were dogmatically tied to a single theory or would not test their theory against alternatives. It is for this purpose that, on the occasion of the nonagenarian celebration of Popper's birthday, the present essay has been written. (shrink)

L'article montre que l'idée développée par Popper dans The Open Universe, et reprise par d'autres, selon laquelle la physique moderne serait foncièrement indéterminisme, repose en réalité sur une conception erronée du déterminisme. Popper n'a pas de mal à montrer que l'état initial d'un système n'étant jamais connu avec une précision absolue, il est impossible de prédire avec certitude son évolution future. Mais cela ne signifie pas pour autant que le déterminisme soit réfuté. Popper s'est attaqué à une des conséquences du (...) déterminisme, à savoir la prédictïbilité universelle, mais il laisse intact le coeur même de la doctrine du déterminisme, c'est-à-dire l'idée que chaque événement suit de manière univoque celui qui le précède. La mécanique classique est déterministe, la relativité restreinte est déterministe, et la mécanique quantique elle-même, à condition toutefois de laisser de côté l'épineux problème de l'opération de mesure, est déterministe. The article deals with an idea developed by Popper in The Open Universe, and supported afterwards by some others. Indeed, according to them, modern physics would be basically indeterministic. This idea rests in fact on a wrong conception of determinism. Popper has no difficulty in showing that, as the initial state of a system is never known with an absolute accuracy, one cannot predict with certainty what will come of it But that does not mean that determinism is refuted Popper has critized one of the consequences of determinism, that is universal predictibility, but he retains the main idea of the doctrine of determinism, which means that each event follows univocally the one which preceeds it. Classical mechanics is deterministic, special relativity is deterministic, and quantum mechanics itself is deterministic too, provided that the difficult problem of the act of measurement is put aside. (shrink)

This paper presents an analysis of several experimental tests of Einstein's theories, together with their Popperian evaluation and a discussion of Einstein's reaction to these tests. It is shown that several relevant refutations of Einstein's theories were not accepted by Einstein as significant, and that therefore Einstein did not follow Popper's methodological rules. This is regarded as a strong case against Popper's criterion of demarcation.

Die Frage der Erhaltung der Parität bei der Wechselwirkung von Elementarteilchen, der Vorschlag ihrer Verletzung, die experimentelle Bestätigung dieses Vorschlags und die daraus sich ergebenden Folgerungen, die zur Formulierung der mathematischen Struktur der schwachen Wechselwirkungen führten, sind die wichtigsten Entwicklungen in der Elementarteilchenphysik während der Periode von 1953 bis 1958. Vorliegender Aufsatz versucht die rationale Rekonstruktion dieser Periode und des Forschungsprogrammes, welches als eines der progressivsten Programme der modernen Physik angesehen wird. Hierzu benutzen wir eine modifizierte Fassung von Poppers tetradischem (...) Schema als auch die Bemerkungen von Lakatos über gewisse Aspekte der Methodologie von Forschungsprogrammen. Es wird unterstrichen, daß die Dynamik der positiven Heuristik derart war, daß die theoretische Forschung fortgeführt werden konnte, trotz experimenteller Resultate, die nur als Gegenbeweise gegen die vorgeschlagene Struktur der schwachen Wechselwirkungen angesehen werden konnten. (shrink)

The basic theme of Popper's philosophy--that something can come from nothing--is related to the present situation in physical theory. Popper carries his investigation right to the center of current debate in quantum physics. He proposes an interpretation of physics--and indeed an entire cosmology--which is realist, conjectural, deductivist and objectivist, anti-positivist, and anti-instrumentalist. He stresses understanding, reminding us that our ignorance grows faster than our conjectural knowledge.

Summary The present paper constitutes an elaboration of a previous work by one of us which, among other things, proposed some modifications of Popper's tetradic schema. Here, in the first part, we consider critically and develop further these modifications and elaborate on methods which prove more satisfactory for the mapping of the problem solving processes in Physics. We also find the opportunity to make some comments on Physics and on its relation to Mathematics. In the second part, there is an (...) attempt to test the above ideas on the genesis and development of the Special Relativity Theory. In doing this, we concentrate mainly on Einstein's 1905 paper and try to explicitate its relation with the situation Physics found itself in that period as well as to clarify the epistemological status of Einstein's two postulates. (shrink)

Gemeinsamkeiten und Unterschiede in den Interpretationen von Ludwig und Popper werden aufgezeigt. Daß überhaupt Unterschiede festzustellen sind, erscheint zunächst verwunderlich, da zum einen von verschiedenen Autoren eine enge Korrelation zwischen Interpretationen der Quantenmechanik und Wahrscheinlichkeitsinterpretationen behauptet wird, zum anderen aber Ludwigs Chancengewichtungen als propensities im Sinne Poppers interpretiert werden können. Es zeigt sich, daß die Unterschiede in den Interpretationen der Quantenmechanik auf Unterschieden in dem jeweils verwendeten wahrscheinlichkeitstheoretischen Formalismus beruhen, die jedoch für die Möglichkeit, Chancengewichtungen als propensities zu interpretieren, ohne (...) Bedeutung sind. (shrink)

Several philosophers of science have claimed that the conceptual difficulties of quantum mechanics can be resolved by appealing to a particular interpretation of probability theory. For example, Popper bases his treatment of quantum mechanics on the propensity interpretation of probability, and Margenau bases his treatment of quantum mechanics on the frequency interpretation of probability. The purpose of this paper is (i) to consider and reject such claims, and (ii) to discuss the question of whether the ψ -function refers to an (...) individual system or to an ensemble of systems. (shrink)