The concept of intelligibility in modern physics (1948)

This is an English translation of Paul Feyerabend's earliest extant essay “Der Begriff der Verständlichkeit in der modernen Physik” (1948). In it, Feyerabend defends positivism as a progressive framework for scientific research in certain stages of scientific development. He argues that in physics visualizability (Anschaulichkeit) and intelligibility (Verständlichkeit) are time-conditioned concepts: what is deemed visualizable in the development of physical theories is relative to a specific historical context and changes over time. He concludes that from time to time the abandonment of visualizability is crucial for progress in physics, as it is conducive to major theory change, illustrating the point on the basis of advances in atomic theory.     

Le Dosage Spectrométrique du Mercure dans l'Air vers 1930

In the 1930s, atomic absorption spectroscopy replaced chemical methods for determining the amount of mercury in atmospheric air. The overall state of chemical analysis was favourable: physical instruments were moving into the chemical laboratory. This new method emerged from work in quantitative physics, and it met a need arising from the risk encountered by those who handled mercury. The new spectrometer, which originally functioned as a detector, also made precise and rapid quantitative determinations possible. This in turn encouraged industrialists to take out patents and make commercial use of the method after various improvements. This method is considered to be the ancestor of modern atomic absorption spectroscopy, which developed independently after 1960. The method developed in the 1930s could only be used for gaseous mercury, and it was not generalized as a method for quantifying other elements. The determination of mercury in air by atomic absorption spectroscopy was the first application of this technique; indeed, it was the only example of a specific use of atomic absorption. It was also part of the instrumental revolution.     

Explaining Atomic Spectra within Classical Physics: 1897-1913

In this paper we analyse the approach to interpreting atomic spectra in the framework of classical physics from the discovery of the electron in 1897 to Bohr's atomic model of 1913. Taken as a whole, efforts in this direction are part of a remarkable intellectual endeavour in which the classical theoretical framework seems to have been exploited to its full potential. By demonstrating the limits and weaknesses of classical physics in solving the problem of spectral emissions, these attempts opened the way to a complete break from traditional thought and the introduction of the new quantum ideas.     

The isotope effect: Prediction,discussion, and discovery

The precise position of a spectral line emitted by an atomic system depends on the mass of the atomic nucleus and is therefore different for isotopes belonging to the same element. The possible presence of an isotope effect followed from Bohr's atomic theory of 1913, but it took several years before it was confirmed experimentally. Its early history involves the childhood not only of the quantum atom, but also of the concept of isotopy. Bohr's prediction of the isotope effect was apparently at odds with early attempts to distinguish between isotopes by means of their optical spectra. However, in 1920 the effect was discovered in HCl molecules, which gave rise to a fruitful development in molecular spectroscopy. The first detection of an atomic isotope effect was no less important, as it was by this means that the heavy hydrogen isotope deuterium was discovered in 1932. The early development of isotope spectroscopy led to successes as well as problems. At the end of the paper I briefly comment on the relationship between theory, experiment and prediction in this area of spectral physics.     

Pluralism and anarchism in quantum physics: Paul Feyerabend's writings on quantum physics in relation to his general philosophy of science

This paper aims to show that the development of Feyerabend's philosophical ideas in the 1950s and 1960s largely took place in the context of debates on quantum mechanics.In particular, he developed his influential arguments for pluralism in science in discussions with the quantum physicist David Bohm, who had developed an alternative approach to quantum physics which (in Feyerabend's perception) was met with a dogmatic dismissal by some of the leading quantum physicists. I argue that Feyerabend's arguments for theoretical pluralism and for challenging established theories were connected to his objections to the dogmatism and conservatism he observed in quantum physics.However, as Feyerabend gained insight into the physical details and historical complexities which led to the development of quantum mechanics, he gradually became more modest in his criticisms. His writings on quantum mechanics especially engaged with Niels Bohr; initially, he was critical of Bohr's work in quantum mechanics, but in the late 1960s, he completely withdrew his criticism and even praised Bohr as a model scientist. He became convinced that however puzzling quantum mechanics seemed, it was methodologically unobjectionable – and this was crucial for his move towards ‘anarchism’ in philosophy of science.     

Epistemology of a believing historian: Making sense of Duhem's anti-atomism

Pierre Duhem's (1861–1916) lifelong opposition to 19th century atomic theories of matter has been traditionally attributed to his conventionalist and/or positivist philosophy of science. Relatively recently, this traditional view position has been challenged by the claim that Duhem's opposition to atomism was due to the precarious state of atomic theories during the beginning of the 20th century. In this paper I present some of the difficulties with both the traditional and the new interpretation of Duhem's opposition to atomism and provide a new framework in which to understand his rejection of atomic hypotheses. I argue that although not positivist, instrumentalist, or conventionalist, Duhem's philosophy of physics was not compatible with belief in unobservable atoms and molecules. The key for understanding Duhem's resistance to atomism during the final phase of his career is the historicist arguments he presented in support of his ideal of physics.     

Measurement in French Experimental Physics from Regnault to Lippmann. Rhetoric and Theoretical Practice

This paper explores the legacy of the great French experimental physicist Victor Regnault through the example of Gabriel Lippmann, whose engagement with electrical standardization during the early 1880s was guided by Regnault's methodological precept to measure ‘directly’. Lippmann's education reveals that the theoretical practice of ‘direct’ measurement entailed eliminating extraneous physical effects through the experimental design, rather than, like physicists in Britain and Germany, making numerical ‘corrections’ to measured values. It also provides, paradoxically, exemplars of the qualitative theoretical practices that sustained Regnault's misguided ambition to avoid theory. By considering the largely negative reactions to Lippmann's proposals for selecting suitable electrical units and methods of measuring the ohm, this paper associates these theoretical practices with the ineffectual rhetorical strategies employed by Lippmann to promote his work, and thereby indicates that the practice of direct measurement was limited to French experimental physics. Whilst this result aligns readily with the existence of divergent nineteenth century British and German cultures of precision, it emerges from a very different disciplinary context in which the practice of precision electrical measurement developed independently of submarine telegraphy. This is because, as this paper illustrates, telegraphic engineering and experimental physics remained separate professions in France.     

Chemical reductionism revisited: Lewis, Pauling and the physico-chemical nature of the chemical bond

The wave-mechanical treatment of the valence bond, by Walter Heitler and Fritz London, and its ensuing foundational importance in quantum chemistry has been traditionally regarded as the basis for the argument that chemistry may be theoretically reduced to physics. Modern analyses of the reductionist claim focuses on the limitations to achieving full reduction in practice because of the approximations used in modern quantum chemical methods, but neglect the historical importance of the chemical bond as a chemical entity. This paper re-examines these arguments with a study of the development of the valence bond by chemist Gilbert Lewis within a chemically autonomous framework, and its extension by Linus Pauling using Heitler and London’s methods. Here, we see that the chemical bond is best described as a theoretical synthesis or physico-chemical entity, to represent its full interdisciplinary importance from the philosophical and historical perspectives.     

Integral equations between theory and practice: the cases of Italy and France to 1920

In 1899, Ivar Fredholm discovered how to treat an integral equation using conceptual methods from linear algebra and use these ideas to solve certain classes of boundary value problems. He formulated a theory allowing him both to unify large classes of problems and to attack several problems fruitfully. The historical literature on the theory of integral equations has concentrated largely on the unification that was afforded by Hilbert and his school, but has not throughly investigated the roots of the subject in the older theory of partial differential equations, as developed for instance by Fredholm himself but also by Volterra and Levi-Civita. By concentrating on work issuing from this older tradition, in particular on French and Italian work, the paper shows how the new theory of integral equations was enthusiastically received, especially for its fruitful applications to areas of mathematical physics such as hydrodynamics, elasticity, and heat theory.     

Solving the Giant Stars Problem: Theories of Stellar Evolution from The 1930s to The 1950s

Historiography has pointed out that the time between the mid 1910s and the early 1930s can be considered a pivotal period in the history of stellar astrophysics. In those years, scholars like Saha and Eddington first applied atomic physics to astrophysics. Theoretical astrophysics was born. This led to the development of the first physically sound models for stellar interiors and atmospheres. These landmark achievements spurred scholars to elaborate theories for stellar evolutions, and in the following decades several astrophysicists focused on this problem. The evolutionary role of red giants turned out to be the main issue. Those stars were initially assumed to be young ones going through the formation stage, but astrophysicists gradually realized that they were rather to be considered old, evolved stars. The solution of the giant stars issue required a couple of decades: it was not until the mid 1950s that a satisfactory explanation was obtained. This provides a detailed picture of the theories of stellar evolution from the 1930s to the 1950s and of the solution to the red giants problem, with special emphasis on how such a solution was made possible by a series of subsequent steps: the identification of changing chemical composition as a main evolutionary feature of a star, the inclusion of nuclear physics within the theoretical framework of stellar astrophysics, the recognition of the importance of inhomogeneities that settle within stars as nuclear processes go on.     

On Mach on time

Mach's views on the nature of time have been unduly neglected. They are both more defensible in their own historical context and more relevant to our own contemporary context than has been appreciated. This essay provides an extended and comprehensive discussion of Mach's writings on time offering novel analysis and interpretation. Contra the prevailing current in the secondary literature, Mach's views on time are shown to be largely vindicated in the context of late nineteenth century physics. Then, building upon this more historical project, we conclude with a critical evaluation of the modern Machian view of time due to Barbour within the context of relativistic chronometry as instantiated via pulsar clocks and atomic clocks. Once more, considered analysis serves to support the Machian view. About time we go back to Mach.     

From aether impulse to QED: Sommerfeld and the Bremsstrahlen theory

The radiation that is due to the braking of charged particles has been in the focus of theoretical physics since the discovery of X-rays by the end of the 19th century. The impact of cathode rays in the anti-cathode of an X-ray tube that resulted in the production of X-rays led to the view that X-rays are aether impulses spreading from the site of the impact. In 1909, Arnold Sommerfeld calculated from Maxwell׳s equations the angular distribution of electromagnetic radiation due to the braking of electrons. He thereby coined the notion of “Bremsstrahlen.” In 1923, Hendrik A. Kramers provided a quantum theoretical explanation of this process by means of Bohr׳s correspondence principle. With the advent of quantum mechanics the theory of bremsstrahlung became a target of opportunity for theorists like Yoshikatsu Sugiura, Robert Oppenheimer, and–again–Sommerfeld, who presented in 1931 a comprehensive treatise on this subject. Throughout the 1930s, Sommerfeld׳s disciples in Munich and elsewhere extended and improved the bremsstrahlen theory. Hans Bethe and Walter Heitler, in particular, in 1934 presented a theory that was later regarded as “the most important achievement of QED in the 1930s” (Freeman Dyson). From a historical perspective the bremsstrahlen problem may be regarded as a probe for the evolution of theories in response to revolutionary changes in the underlying principles.     

How physics flew the philosophers' nest

We all know that, nowadays, physics and philosophy are housed in separate departments on university campuses. They are distinct disciplines with their own journals and conferences, and in general they are practiced by different people, using different tools and methods. We also know that this was not always the case: up until the early 17th century (at least), physics was a part of philosophy. So what happened? And what philosophical lessons should we take away? We argue that the split took place long after Newton's Principia (rather than before, as many standard accounts would have it), and offer a new account of the philosophical reasons that drove the separation. We argue that one particular problem, dating back to Descartes and persisting long into the 18th century, played a pivotal role. The failure to solve it, despite repeated efforts, precipitates a profound change in the relationship between physics and philosophy. The culprit is the problem of collisions. Innocuous though it may seem, this problem becomes the bellwether of deeper issues concerning the nature and properties of bodies in general. The failure to successfully address the problem led to a reconceptualization of the goals and subject-matter of physics, a change in the relationship between physics and mechanics, and a shift in who had authority over the most fundamental issues in physics.     

The quantum Hall effects: Philosophical approach

The Quantum Hall Effects offer a rich variety of theoretical and experimental advances. They provide interesting insights on such topics as gauge invariance, strong interactions in Condensed Matter physics, emergence of new paradigms. This paper focuses on some related philosophical questions. Various brands of positivism or agnosticism are confronted with the physics of the Quantum Hall Effects. Hacking׳s views on Scientific Realism, Chalmers׳ on Non-Figurative Realism are discussed. It is argued that the difficulties with those versions of realism may be resolved within a dialectical materialist approach. The latter is argued to provide a rational approach to the phenomena, theory and ontology of the Quantum Hall Effects.     

信息几何理论与应用研究进展

信息几何是在Riemann流形上采用现代微分几何方法来研究统计学问题的基础性、前沿性学科，被誉为是继Shannon开辟现代信息理论之后的又一新的理论变革，在信息科学与系统理论研究领域展现出了巨大的发展潜力．本文首先从参数化概率分布族的内蕴几何结构特征与信息的几何性质出发，精炼了信息几何的科学内涵，指出信息几何相比于经典统计学与信息论的理论优势与方法的革新．然后简要阐述了信息几何与微分几何的联系，综述了信息几何理论的发展历史与近20年来信息几何在神经网络、统计推断、通信编码、系统理论、物理学和医学成像等各领域应用的研究现状，归纳和总结了其中所体现的信息几何的基本原理和基本方法，并对信息几何的发展给予注记．特别地，对信息几何在信号处理领域中的应用成果进行了较全面的总结和概括，阐述了信息几何在信号检测、参数估计与滤波等方面的最新研究成果．最后，展望信息几何的发展前景，提出了信息几何在信号处理领域中的若干开放性问题．     

Econophysics for philosophers

In this essay review article I present a philosophers’ guide to econophysics, a relatively new field that applies the concepts and methods of statistical physics (and, more generally, other areas of physics) to economics (especially the economics of financial markets). I do this by looking at eleven recent books on econophysics.     

非线性量子力学的建立

笔者在长期研究工作的基础上,从提出非线性量子力学的基本原理出发,建立起了非线性量子力学理论,形成了完整的非线性量子力学的理论体系。从而把量子力学从线性领域推广和发展到非线性领域。在本文中笔者描述了建立这个非线性量子力学的物理背景,它的基本构思,研究的技术路线,产生的实际效果,与国际同类研究比较,本研究的创新和特点以及研究的重大意义。