If, as is universally acknowledged, the proper goal of the mathematical sciences is the discovery of the least possible number of principles (notably principles that are not further explicable) from which the universal laws of empirically given facts emerge with mathematical necessity, and thus the discovery of principles equivalent to those empirical facts, then it must appear as a duty of indubitable importance to reflect carefully on the principles that have already surfaced with some certainty in one area of the natural sciences and present them in a form that really fulfills the equivalence requirement.

Gravitational redshift of spectral lines as one of the three early-known experimental implications of Einstein's general theory of relativity and gravitation was intensively searched for by researchers all over the world, but around 1920 most of the contemporary evidence in the sun's Fraunhofer-spectrum conflicted with the predictions of relativity theory.

In 1923 the American astrophysicist Charles Edward St. John announced that his own solar spectroscopic data would force him to retreat from his former skepticism concerning the existence of gravitational redshift. This statement was at the time widely interpreted by scientists and journalists alike as the open confession of a rapid conversion of one of the few remaining serious scientific opponents of Einstein's theory.

This paper demonstrates that this illusion of a sudden “Gestalt switch” in St. John's evaluation of data can be dissolved by a careful step-by-step account of St. John's research practice between 1917 and 1923. After a fine-grained diachronic report of the development of St. John's interpretation of his and others' data, the second part of the paper consists in a systematic analysis of the heuristics and arguments used by St. John pro and contra gravitational redshift.

The question of the possible existence of black holes is closely related to the question of the action of gravitation on the propagation of light. It has been raised recurrently from the when that Newton referred to a possible bending of light in his Opticks. And it relies on apparently simple questions: Is light subject to gravitation? What is the effect of a gravitational field on the propagation of light? Could a particle of light emitted by a star be retained by its gravitational field?

From the end of the 1960s, the black hole idea has had a very important place in the relativistic literature, not to speak of the popularization of the theory. It turned out to be not only an important concept but also a tool that permitted us to understand general relativity better, indeed a tool that contributed greatly to changing the interpretation of Einstein's theory of gravitation. Here too I want to use this concept of the black hole to assist our understanding of the history of general relativity: the black hole is a fundamental milestone in the evolution of general relativity.

In this paper I present and argue for a model of conceptual development in science and apply it to the transition from classical to modern physics associated with Einstein. The model claims a continuous and rational transition between incompatible subsequent conceptual systems in mathematical science and explains its mechanism. The model was developed in a study of the transition from preclassical to classical mechanics. I argue for a strong structural analogy between the transition from preclassical to classical mechanics on the one hand and from classical to modern physics on the other. The first transition is briefly sketched here by reference to Galileo and his disciples; in the second transition Planck and Lorentz on the one hand and Einstein on the other play the respective roles.

A detailed and documented reconstruction of the transition from preclassical to classical mechanics on the basis of this model has already been published and is only briefly referred to in the paper. The transition from classical to modern physics is portrayed here much more extensively—though of course merely in broad brush strokes. Einstein–s role in this transition is reconstructed in the light of a conceptualization of his scientific knowledge as an active structure of thought, shaped by his intellectual experience. In this way, the development of his individual thinking is shown to be part of the overall process of conceptual transformation from classical to modern physics. The reconstruction sketched in this paper is to be considered as a proposal to be substantiated, reformed, and improved by future detailed studies.

This paper argues that Einstein subscribed to three distinct kinds of interpretations of the quantum theory: subjective, instrumental, and hidden variables interpretations. We explore the context and ihe content of Einstein's thinking over these interpretations, emphasizing Einstein's conception of his role not only as a critic of the new quantum theory but also as a guide pointing the way to better physics.

Albert Einstein had more than a passing and trivial involvement with patents and inventions. The historian seeking to fathom Einstein's thought processes would be ill-advised to pass lightly over his years at the Swiss Federal Patent office (1902–1909) and to consider his professional advice-giving about patents and his patenting of his inventions as merely peripheral to his core concerns and cognitive style. Years of reading patents and visualizing the machines, devices, and electromagnetic phenomena described in them is a formative experience. A number of inventors besides Einstein enhanced their power of visualization from reading and writing patent claims. It is reasonable to conclude that the Patent Office years honed his remarkable gift for visually conceptualizing systematic artifactual relationships that he used in articulating theory.

Developments in theoretical physics, even when they are revolutionary for physics, usually do not enter public awareness. The reaction to the special relativity theory is one of the few exceptions. The conceptual changes brought by special relativity to our notions of space and time, induced a lively debate not only within intellectual circles but in many strata of the educated middle class. In this article, I focus on a particular moment of public reaction to special and general relativity theory and to its creator Albert Einstein. I try to paint a picture of the anti-Einstein campaign in Germany of 1920, with finer brush strokes than those applied previously by others. My aim is to embed the campaign into the cultural and political climate of the Weimar republic. Without leaving the realm of physics only a superficial understanding of what happened seems possible. My thesis is that the anti-Einstein-campaign was organized, and the physicists involved in it (ab)used, mainly in order to rally support for one of the German right-wing parties, the Deutschnationale Volkspartei.

Soon after finishing his studies in 1900, Einstein makes a tactical retreat to the Patent Office in Bern where he develops a plan for returning to the academic fold. He is assisted in this by a central figure in the Zurich establishment, Alfred Kleiner, who grooms him for the return. More generally, I argue that Einstein's role in the emergence of theoretical physics as a discipline results from the interaction of two developments, one external and institutional, the other internal and personal. Certain institutional constraints influence Einstein's early academic career by providing a professional opportunity to which he can adjust his career plans. The existence of this professional context for Einstein's early work in physics plays a role in encouraging him to pursue the speculative work in physics that became his distinctive hallmark. The other side of the coin is that Einstein's personal legitimation as professor of theoretical physics in 1909 also confers legitimacy on his speculative research, which in turn infuses the term “theoretical physics” with new meaning. The key factor uniting Einstein's personal development with institutional opportunities is the special relationship that he enjoys with Kleiner, who serves as the focus of interactions between the external and internal developments described in the paper.

A discussion of the circumstances of the friendship between Einstein and Lorentz using published and unpublished sources provides material for a close analysis of their relationship. In this analysis the concept of distance, both in a physical and a psychological sense, plays a central and clarifying role. It is concluded that for Einstein the distance between him and Lorentz was essential for the relationship to become as rich and intense as it was.

The aim of this paper is to provide a critical perspective for Einstein's opposition to the Copenhagen interpretation of quantum physics, by analyzing the ingenious rhetoric of Bohr's principle of complementarity. I argue that what Bohr presents as arguments of “inevitability” are in fact merely arguments for the consistency of the quantum-mechanical scheme. Einstein's resistance to being persuaded by this potent technique of argumentation, and his rejection of Bohr's interpretation of quantum physics, appear consequently as an eminently reasonable position and not as a conservative stand, as it is often presented by the adherents of the Copenhagen orthodoxy.

Carl Gottfried Neumann was born in Königsberg, Prussia, in 1832 and died in Leipzig in 1925. His father was the physicist Franz Neumann (1798–1895), notable for his contributions not only to the study of electricity and magnetism but also to the development of physics education in nineteenth-century Germany. Carl Neumann studied at the University of Königsberg and received his doctorate in 1855 with a work on the application of elliptic integrals to mechanics (Neumann 1856). In 1858 he became Privatdozent, and in 1863 Professor of Mathematics at Halle. Later that same year he moved to Basel, and in 1865 he became Ordinary Professor of Mathematics at Tübingen. Finally in 1868 he was appointed Professor of Mathematics at Leipzig, a post he held until he retired in 1911; of the two mathematics professorships at Leipzig, this was the one formerly held by F. A. Möbius, and it was officially devoted to “the higher mathematics, especially physics” (quoted in Jungnickel and McCormmach 1986, 1:181). So Neumann's academic career, along with his role as one of the founding editors of the Mathematische Annalen beginning in 1869, can be seen as reflecting the enormous advance in mathematical sophistication that German physics underwent in the latter part of the nineteenth century.

This paper is about the context of Albert Einstein's concerns at the time of a most intense intellectual effort — his own and that of a small group of scientists concerned with classical quantum theory. I describe contemporaneous interactions and differing views about the prospects for and the significance of the First Solvay Congress of 1911 as voiced by major participants. There are two axes around which the paper evolves: the Einstein-Nernst-Lorentz dialogue and the public institutional creation of the “Solvay” stage. In certain ways, this paper is about personal and institutional patronage: the working out of a difficult theoretical impasse requires individual and collective moral support. It is about the forging of the identity of a scientific problem and the personal and institutional setting, the public space, in which this problem was collectively addressed. But I also uncover heuristic playfulness and flexibility which accompanies theoretical change.

Einstein's concept of causality as analyzed in this paper is a thick concept comprised of: (a) regularity; (b) locality; (c) symmetry considerations leading to conservation laws; (d) mutuality of causal interaction. The main theses are: 1. Since (b)–(d) are not elements of Hume's concept of causality, Einstein's concept, the concept embedded in the theory of relativity, is manifestly non–Humean. 2. On a Humean conception, Newtonian mechanics is a paradigmatically causal theory. Einstein, however, regarded this theory as causally deficient, for it fails to comply with both (b) and (d). Special relativity was (partly) motivated by the wish to correct the first of these failures; general relativity the second. 3. Ironically, general relativity, based on the thick concept of causality, opens the way for a conventionalist understanding of that concept. 4. With regard to human freedom, Einstein professed to be a Spinozist. However, he suggested a version of soft determinism, not found in Spinoza.

Einstein's mass-energy relationship was not confirmed experimentally until 1933 when Bainbridge showed that the Cockcroft-Walton experiment afforded a test of it. Earlier, however, it had been used constantly in the analysis of nuclear reactions, as can be seen in those involved in the determination of the mass of the neutron. Chadwick in 1932 was convinced that the neutron mass was about 1.0067 amu (atomic mass units), indicating that the neutron was a proton-electron compound, since that figure was less than the sum of the proton and electron masses. Chadwick's value was challenged in 1933 by Lawrence, who proposed a much lower value of 1.0006 amu, and by Curie and Joliot, who proposed a much higher value of 1.011 amu.Much controversy ensued; eventually, Chadwick and Goldhaber showed in 1934 that the neutron mass was about 1.0080 amu, greater than the sum of the proton and electron masses, proving that the neutron was a new elementary particle (which could decay spontaneously), and providing conclusive experimental support for excluding electrons from the nucleus. These results remained unchanged with further refinements in the last decimal place, the entire pursuit of which provided still further vindication of Einstein's massenergy relationship.