This paper expounds the modern theory of symplectic reduction in finite-dimensional Hamiltonian mechanics. This theory generalizes the well-known connection between continuous symmetries and conserved quantities, i.e. Noether's theorem. It also illustrates one of mechanics' grand themes: exploiting a symmetry so as to reduce the number of variables needed to treat a problem. The exposition emphasises how the theory provides insights about the rotation group and the rigid body. The theory's device of quotienting a state space also casts light on philosophical (...) issues about whether two apparently distinct but utterly indiscernible possibilities should be ruled to be one and the same. These issues are illustrated using ``relationist'' mechanics. (shrink)

For over a century the definitions of mass and derivations of its relation with energy continue to be elaborated, demonstrating that the concept of mass is still not satisfactorily understood. The aim of this study is to show that, starting from the properties of Minkowski spacetime and from the principle of least action, energy expresses the property of inertia of a body. This implies that inertial mass can only be the object of a definition—the so called mass-energy relation—aimed at measuring (...) energy in different units, more suitable to describe the huge amount of it enclosed in what we call the “rest-energy” of a body. Likewise, the concept of gravitational mass becomes unnecessary, being replaceable by energy, thus making the weak equivalence principle intrinsically verified. In dealing with mass, a new unit of measurement is foretold for it, which relies on the de Broglie frequency of atoms, the value of which can today be measured with an accuracy of a few parts in 109. (shrink)

In this paper I draw on Einstein's distinction between “principle” and “constructive” theories to isolate two levels of physical theory that can be found in both classical and (special) relativistic physics. I then argue that when we focus on theoretical explanations in physics, i.e. explanations of physical laws, the two leading views on explanation, Salmon's “bottom-up” view and Kitcher's “top-down” view, accurately describe theoretical explanations for a given level of theory. I arrive at this conclusion through an analysis of explanations (...) of mass—energy equivalence in special relativity. (shrink)

Raspravljamo o ulozi predpojmovnog kompleksnog mišljenja u znanstvenoj spoznaji i razvoju znanosti. Kompleksno mišljenje sa svom heterogenošću i imaginacijom omogućuje održavanje pojmovne strukture i reorganizaciju cjelokupnih teorijskih mreža, ali to “naplaćuje” latentnim prisustvom protuslovlja i nekonzistentnosti.Članak se nastavlja na našu analizu odnosa između kompleksnog i pojmovnog mišljenja u Aristotelovoj Fizici. Ako je kod Aristotela središnji kompleks pojam “mjesta”, kod Galileija je osnovni kompleks zbirka gibanja-stanja. Galilei još nema izrađenu potpunu pojmovnu strukturu mehanike pa možemo reći da je njegova teorijska osnova (...) uronjena u kompleksnu razinu, ali se oslanja na matematičku strukturu i eksperiment i time uspijeva formirati jednu stabilnu teorijsku organizaciju. Time dobiva osnovu za novu teorijsku sistematizaciju i za formiranje pojmovne strukture kakva je Newtonova. Možemo u izvjesnom smislu reći da je time kompleksno mišljenje u znanosti bilo podignuto na višu razinu i dovedeno u pred-paradigmično razdoblje.We discuss the role of the pre-conceptual complex thought in scientificknowledge and in the development of science. The heterogeneity and imagination of complex thought enables the preservation of the conceptual structure and helps reshape entire theoretical nets, however, its downside is reflected in its latent contradiction and inconsistency. This paper is a continuation of our analysis of the relationship between complex and conceptual thought in Aristotle’s Physics. If Aristotle’s central complex is the notion of “place”, then Galileo’s basic complex is the notion of “ movement”. Since Galileo didn’t have an elaborated conceptual structure of mechanics, we can say that his theoretical basis is “steeped” in the level of complex thought, yet it relies on the mathematical structure and experiment, thereby creating a stable theoretical organization which serves as a basis for the new theoretical systematization and for the shaping of a conceptual structure as Newton’s. Thus, we may claim that, in a certain way, this change raised complex thought in science to a higher level, and brought it to a pre-paradigmatic period. (shrink)

This paper develops a new version of instrumentalism, in light of progress in the realism debate in recent decades, and thereby defends the view that instrumentalism remains a viable philosophical position on science. The key idea is that talk of unobservable objects should be taken literally only when those objects are assigned properties (or described in terms of analogies involving things) with which we are experientially (or otherwise) acquainted. This is derivative from the instrumentalist tradition in so far as the (...) distinction between unobservable and observable is taken to have significance with respect to meaning. (shrink)

This paper is part II of a trilogy on the transition from classical particle mechanics to relativistic continuum mechanics that one of the authors is working on. The first part, on the Trouton experiment, was published in the Stachel festschrift (Janssen 2003). This paper focuses on the Lorentz-Poincaré electron, and, in particular, on the "Poincaré pressure" or "Poincaré stresses" introduced to stabilize the electron. It covers both the original argument by Poincaré (1906) and a modern relativistic argument for adding a (...) negative pressure term to the system's energy-momentum tensor inspired by the work of Laue (1911a, b). It highlights the importance of a paper by Lorentz (1899) in this context and of the "electromagnetic mechanics" of Abraham (1903). (shrink)

The historical development of the famous Einstein formula \ is briefly discussed. In this paper, on the basis of the Einstein viewpoint a new general approach is proposed for demonstrating the correctness of the formula \ . It is can be seen that the generalized approach leads to Einstein’s famous formula, too. During recent years, various papers have been published concerning the incompleteness of this famous formula. It is demonstrated that the presented claims in these articles are not mathematically legitimate. (...) It is clear that there are still some important misunderstandings concerning the interpretation of Einstein’s mass-energy equivalence formula. (shrink)

This paper will examine the implications of an extended “field theory of information,” suggested by Wolfhart Pannenberg, specifically in the Christian understanding of creation. The paper argues that the Holy Spirit created the world as field, a concept from physics, and the creation is directed by the logos utilizing information. Taking into account more recent developments of information theory, the essay further suggests that present creation has a causal impact upon the information utilized in creation. In order to adequately address (...) Pannenberg's hypothesis that the logos utilizes information at creation the essay will also include an introductory examination of Pannenberg's Christology which shifts from a strict “from below” Christology, to a more open “third way” of doing Christology beyond “above” and “below.” The essay concludes with a brief section relating the implications of an extended “field theory of information” to creative inspiration, as well as parallels with human inspiration. (shrink)

Presented here is an overview from the standpoints of sociology, history of science, philosophy of science and “pure science” of the lingering question of whether sociology is a form of scientific pursuit. The conclusion is drawn that sociology barely meets any of the rigid criteria traditionally associated with the natural sciences. Sociology is viewed as having a position of theory and argument which is labeled “inconoclastic scepticism.”.