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)

During the last three decades, there has been a growing realization among physicists and cosmologists that the relation between particle physics and cosmology may constitute yet another successful example of the unity of science. However, there are important conceptual problems in the unification of the two disciplines, e.g. in connection with the cosmological constant and the conjecture of inflation. The present article will outline some of these problems, and argue that the victory for the unity of science in the context (...) of cosmology and particle physics is still far from obvious. (shrink)

I critically discuss a controversial ‘trans-Planckian censorship’ conjecture, which has recently been introduced to researchers working at the intersection of fundamental physics and cosmology. My focus explicitly avoids any appeals to contingent research within string theory or regarding the more general gravitational ‘swampland’. Rather, I concern myself with the conjecture’s foundations in our current, well-trodden physics of quantized fields, spacetime, and gravity. In doing so, I locate what exactly within trans-Planckian censorship amounts to a departure from current physics—identifying what is, (...) ultimately, so conjectural about the conjecture. (shrink)

An equation proposed by Levy, Perdew and Sahni (Phys. Rev. A 30:2745, 1984) is an orbital-free formulation of density functional theory. However, this equation describes a bosonic system. Here, we analyze on a very fundamental level, how this equation could be extended to yield a formulation for a general fermionic distribution of charge and spin. This analysis starts at the level of single electrons and with the question, how spin actually comes into a charge distribution in a non-relativistic model. To (...) this end we present a space-time model of extended electrons, which is formulated in terms of geometric algebra. Wave properties of the electron are referred to mass density oscillations. We provide a comprehensive and non-statistical interpretation of wavefunctions, referring them to mass density components and internal field components. It is shown that these wavefunctions comply with the Schrödinger equation, for the free electron as well as for the electron in electrostatic and vector potentials. Spin-properties of the electron are referred to intrinsic field components and it is established that a measurement of spin in an external field yields exactly two possible results. However, it is also established that the spin of free electrons is isotropic, and that spin-dynamics of single electrons can be described by a modified Landau-Lifshitz equation. The model agrees with the results of standard theory concerning the hydrogen atom. Finally, we analyze many-electron systems and derive a set of coupled equations suitable to characterize the system without any reference to single electron states. The model is expected to have the greatest impact in condensed matter theory, where it allows to describe an N-electron system by a many-electron wavefunction Ψ of four, instead of 3N variables. The many-body aspect of a system is in this case encoded in a bivector potential. (shrink)

In this paper I focus on the impact on structuralism of the quantum treatment of objects in terms of symmetry groups and, in particular, on the question as to how we might eliminate, or better, reconceptualise such objects in structural terms. With regard to the former, both Cassirer and Eddington not only explicitly and famously tied their structuralism to the development of group theory but also drew on the quantum treatment in order to further their structuralist aims and here I (...) sketch the relevant history with an eye on what lessons might be drawn. With regard to the latter, Ladyman has explicitly cited Castellani's work on the group-theoretical constitution of quantum objects and I indicate both how such an approach needs to be understood if it is to mesh with Ladyman's 'ontic' form of structural realism and how it might accommodate permutation symmetry through a consideration of Huggett's recent account. (shrink)