Explaining Models: Theoretical and Phenomenological Models and Their Role for the First Explanation of the Hydrogen Spectrum

Wilholt T. Explaining Models: Theoretical and Phenomenological Models and Their Role for the First Explanation of the Hydrogen Spectrum. Foundations of Chemistry. 2005;7(2):149-169.Traditional nomological accounts of scientific explanation have assumed that a good scientific explanation consists in the derivation of the explanandum's description from theory (plus antecedent conditions). But in more recent philosophy of science the adequacy of this approach has been challenged, because the relation between theory and phenomena in actual scientific practice turns out to be more intricate. This critique is here examined for an explanatory paradigm that was groundbreaking for 20th century physics and chemistry (and their interrelation): Bohr's first model of the atom and its explanatory relevance for the spectrum of hydrogen. First, the model itself is analysed with respect to the principles and assumptions that enter into its premises. Thereafter, the origin of the model's explanandum is investigated. It can be shown that the explained "phenomenon" is itself the product of a host of modelling accomplishments that stem from an experimental tradition related to 19th century chemistry, viz. spectroscopy. The relation between theory and phenomenon is thus mediated in a twofold way: by (Bohr's) theoretical model and a phenomenological model from spectroscopy. In the final section of the paper an account is outlined that nevertheless permits us to acknowledge this important physico-chemical achievement as a case of (nomological) explanation

On the verge of Umdeutung in Minnesota: Van Vleck and the correspondence principle (Part One)

In October 1924, the Physical Review, a relatively minor journal at the time, published a remarkable two-part paper by John H. Van Vleck, working in virtual isolation at the University of Minnesota. Van Vleck combined advanced techniques of classical mechanics with Bohr's correspondence principle and Einstein's quantum theory of radiation to find quantum analogues of classical expressions for the emission, absorption, and dispersion of radiation. For modern readers Van Vleck's paper is much easier to follow than the famous paper by Kramers and Heisenberg on dispersion theory, which covers similar terrain and is widely credited to have led directly to Heisenberg's "Umdeutung" paper. This makes Van Vleck's paper extremely valuable for the reconstruction of the genesis of matrix mechanics. It also makes it tempting to ask why Van Vleck did not take the next step and develop matrix mechanics himself.Comment: 82 page

British participation in the first Solvay Councils on physics

Analysis of the makeup and contributions of the British contingents to the first two Solvay Councils can elucidate the character of British mathematical physics and its internal dynamics at a critical time in its development. The paper provides this analysis, outlines the process of selection of the participants, parses the meaning of “international” in the Solvay context, and offers an explanation of the differential attendance of the British at the two Councils. Most of those invited to the first refused whereas all but one of those invited to the second accepted. The unusual social and scientific views of Ernest Solvay help to explain this divergence