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. (shrink)

In quantum theory, objects are intrinsically evolving and changing based on the Uncertainty Principle, and the particle state is described by a time-dependent wave packet such that the wave packet corresponding to even a free particle is successively evolvable; a quantum particle has an indefinite and transformative state. In the relativistic Quantum Fields Theory, instead of the concepts of particle and wave packet, a continuous object named “field” with permanent fluctuation in its ground state is considered as the original concept. (...) In Mulla Sadra’s philosophy, based on the Substantial Motion Theory, the subject of continuous evolution and change in the natural body appears as the intrinsic mobility of the natural body. In this paper, we are going to present a comparative investigation of this topic in the two areas of study mentioned. Initially, we present some necessary topics in physics including the motion of fundamental particles, the motion of quantum objects, Quantum Fields Theory, quantum vacuum, and the creation and annihilation of particles in the Quantum Fields Theory; then, we consider some necessary topics in some fields of study in philosophy about the natural body and the nature and the identity of physical bodies including the ideas and the special opinion of Mulla Sadra. Particularly and with more detail, we pay attention to the Sadrian philosophy about the evolution and intrinsic mobility of the natural body based on his famous Substantial Motion Theory. With a comparative study, and by considering Sadrian philosophy as the fundamental philosophical basis for natural sciences, particularly physics, we try to compare the intrinsic motion of natural bodies in Mulla Sadra’s philosophy with the intrinsic evolution of quantum objects in modern physics. Our research method is based on and uses standard resources including books and research papers about Mulla Sadra’s thoughts and theories and the internationally well-known books and papers on standard quantum physics and quantum fields theory. The conclusive remarks are as follows: The transformation of quantum particles or the creation and annihilation of particles in the theory of quantum fields agrees with this point that the intrinsic mobility of the natural body in Mulla Sadra’s philosophy doesn’t reason on the philosophical existence and/or loss of existence. That a quantum particle doesn’t have a constant status in two consecutive instants is in agreement with the Sadrian Substantial Motion Theory that explains ‘motion’ in the ‘bed’ of time. Finally, we should mention that although the intrinsic motion of the natural body in Mulla Sadra’s philosophy is based on its completion while the creation and annihilation of particles in Quantum Fields Theory may be better compared with the emergence and extinction well known in peripatetic philosophy, by considering the background quantum vacuum field as the main basis of the so-called “particles” which is continuously in evolution and permanent fluctuation and is the basis for the creation and annihilation of particles, the comparison between the modern Quantum Fields Theory and Mulla Sadra’s philosophy is done well. (shrink)

The paper offers a historical overview of Einstein's oscillating attitude towards a "phenomenological" and "dynamical" treatment of rods and clocks in relativity theory. Contrary to what it has been usually claimed in recent literature, it is argued that this distinction should not be understood in the framework of opposition between principle and constructive theories. In particular Einstein does not seem to have plead for a "dynamical" explanation for the phenomenon rods contraction and clock dilation which was initially described only "kinematically". (...) On the contrary textual evidence shows that, according to Einstein, a realistic microscopic model of rods and clocks was needed to account for the very existence of measuring devices of "identical construction" which always measure the same unit of time and the same unit of length. In fact, it will be shown that the empirical meaningfulness of both relativity theories depends on what, following Max Born, one might call the "principle of the physical identity of the units of measure". In the attempt to justify the validity of such principle, Einstein was forced by different interlocutors, in particular Hermann Weyl and Wolfgang Pauli, to deal with the genuine epistemological, rather then physical question whether a theory should be able or not to described the material devices that serve to its own verification. (shrink)

Niels Bohr’s model of the hydrogen atom is widely cited as an example of an inconsistent scientific theory because of its reliance on classical electrodynamics together with assumptions about interactions between matter and electromagnetic radiation that could not be reconciled with CED. This view of Bohr’s model is controversial, but we believe a recently proposed approach to reasoning with inconsistent commitments offers a promising formal reading of how Bohr’s model worked. In this paper we present this new way of reasoning (...) with inconsistent commitments and compare it with other approaches before applying it to Bohr’s model and offering some suggestions for how it might be extended to account for subsequent developments in old quantum theory. (shrink)

Historians and philosophers of science generally conceptualize scientific progress to be dichotomous, viz., experimental observations lead to scientific laws, which later facilitate the elaboration of explanatory theories. There is considerable controversy in the literature with respect to Mendeleev’s contribution to the origin, nature, and development of the periodic table. The objectives of this study are to explore and reconstruct: a) periodicity in the periodic table as a function of atomic theory; b) role of predictions in scientific theories and its implications (...) for the periodic table; and c) Mendeleev’s contribution: theory or an empirical law? The reconstruction shows that despite Mendeleev’s own ambivalence, periodicity of properties of chemical elements in the periodic table can be attributed to the atomic theory. It is argued that based on the Lakatosian framework, predictions play an important role in the development of scientific theories. In this context, Mendeleev’s predictions played a crucial role in the development of the periodic table. Finally, it is concluded that Mendeleev’s contribution can be considered as an “interpretative” theory which became “explanatory” after the periodic table was based on atomic numbers.Author Keywords: Periodic table; Mendeleev’s contribution; Theory; Empirical law; Interpretative theory. (shrink)

Sir Karl Popper is one of the few authors to have discussed the reduction of chemistry. His approach consists of what I term naturalistic reduction, which I suggest bears close similarities to the way in which scientists regard reduction. The present article aims to build on Popper's insights into the nature of reduction in science and more specifically to suggest an approach to characterizing a specific sense of the notion of approximate reduction in the context of chemistry. In the course (...) of the discussion, one of Popper's better known passages on the reduction of chemistry is analysed in some detail. (shrink)

The historical development of the electronic configuration model is traced and the status of the model with respect to quantum mechanics is examined. The successes and problems raised by the model are explored, particularly in chemical ab initio calculations. The relevance of these issues to whether chemistry has been reduced to quantum mechanics is discussed, as are some general notions on reduction.

The chemical nature of element 72, subsequently named hafnium, is generally regarded as a prediction from Bohr's theory of the periodic system and hence as a prediction from quantum theory. It is argued that both of these views and in particular the latter are mistaken. The claim in favour of Bohr's theory is weakened by his accommodation of independent chemical arguments and the claim in favour of quantum theory is untenable since the prediction is not strictly deductive.

Although the periodic system of elements is central to the study of chemistry and has been influential in the development of quantum theory and quantum mechanics, its study has been largely neglected in philosophy of science. The present article is a detailed criticism of one notable exception, an attempt by Hettema and Kuipers to axiomatize the periodic table and to discuss the reduction of chemistry in this context.