The Ether at the Crossroads of Classical and Modern Physics

This chapter aims to liberate the ether from its historiographical assignment to classical physics, instead considering its role in debates surrounding the future of the discipline. Focusing on the British case, it explores the discussions underway in professional spaces between 1909 and 1914, suggesting that a physicist’s commitment to the ether does not classify them as a ‘classicist’ but rather as an advocate of continuity in the discipline. It then examines the ether’s ‘popular’ life following the well-publicised 1919 eclipse expedition, and the subsequent expository efforts by the ‘classical’ Oliver Lodge and ‘modern’ Arthur Stanley Eddington. By moving beyond a traditional approach that divides physics and physicists into classical and modern, this chapter suggests a more substantial role for the ether in professional and popular early twentieth-century British physics.

The dynamical integrity concept for interpreting/ predicting experimental behaviour: from macro- to nano-mechanics

The dynamical integrity, a new concept proposed by J.M.T. Thompson, and developed by the authors, is used to interpret experimental results. After reviewing the main issues involved in this analysis, including the proposal of a new integrity measure able to capture in an easy way the safe part of basins, attention is dedicated to two experiments, a rotating pendulum and a micro-electro-mechanical system, where the theoretical predictions are not fulfilled. These mechanical systems, the former at the macro-scale and the latter at the micro-scale, permit a comparative analysis of different mechanical and dynamical behaviours. The fact that in both cases the dynamical integrity permits one to justify the difference between experimental and theoretical results, which is the main achievement of this paper, shows the effectiveness of this new approach and suggests its use in practical situations. The men of experiment are like the ant, they only collect and use; the reasoners resemble spiders, who make cobwebs out of their own substance. But the bee takes the middle course: it gathers its material from the flowers of the garden and field, but transforms and digests it by a power of its own. Not unlike this is the true business of philosophy (science); for it neither relies solely or chiefly on the powers of the mind, nor does it take the matter which it gathers from natural history and mechanical experiments and lay up in the memory whole, as it finds it, but lays it up in the understanding altered and digested. Therefore, from a closer and purer league between these two faculties, the experimental and the rational (such as has never been made), much may be hoped. (Francis Bacon 1561–1626) But are we sure of our observational facts? Scientific men are rather fond of saying pontifically that one ought to be quite sure of one's observational facts before embarking on theory. Fortunately those who give this advice do not practice what they preach. Observation and theory get on best when they are mixed together, both helping one another in the pursuit of truth. It is a good rule not to put overmuch confidence in a theory until it has been confirmed by observation. I hope I shall not shock the experimental physicists too much if I add that it is also a good rule not to put overmuch confidence in the observational results that are put forward until they have been confirmed by theory . (Arthur Stanley Eddington 1882–1944)

General Relativity in the English-speaking World: The Contributions of Henry L. Brose

The story of how the theory of general relativity found its way into the English speaking world during the Great War has often been told: it is dominated by the towering figure of the Cambridge astronomer Arthur Stanley Eddington, who (in 1916, and through the good services of the Dutch physicist Willem de Sitter) received copies of the papers Einstein had presented to the Berlin Academy in 1915. Eddington engaged in promoting the new theory, and in order to put one of its predictions — the bending of light in a gravitational field — to the test, he arranged for the famous expeditions to observe the eclipse of 29 May 1919 to be mounted, the results of which, presented in November of the same year, were the major breakthrough of general relativity and provoked a public interest unprecedented in the whole history of science. But a history of general relativity in the English-speaking world would be thoroughly incomplete if it did not take into account the contributions made by another, nowadays almost forgotten but at that time probably the most prolific and most dedicated of its popularizers, the Australian physicist and translator Henry L. Brose. Largely overlooked in recent accounts of the history of general relativity, Brose's rendering into English of a series of excellent German works on the theory was decisive for its understanding in the Anglo-Saxon world. The texts he chose (including Moritz Schlick's Space and Time in Contemporary Physics and Hermann Weyl's Space, Time, Matter) were among the first and most important that had so far appeared on the subject, and their English translations were published at a time when accounts of what was to be called 'one of the greatest of achievements in the history of human thought' were scarce and badly needed in Britain. Also, it will become clear from a closer look at both Brose's biography and the tense political situation between Britain and Germany shortly after the Great War, that hardly any of those works would have made its way into England so promptly (if at all) if not for Brose's enormous personal efforts and dedication. This paper retraces Brose's role as a translator and promotor of general relativity in its early days, thus shedding light on the mechanisms of knowledge transfer during and after the First World War.