Online research in philosophy

The axiomatic approaches of quantum mechanics and relativity theory are compared with approaches in which the theories are thought to describe readings of certain measurement operations. The usual axioms are shown to correspond with classes of ideal measurements. The necessity is discussed of generalizing the formalisms of both quantum mechanics and relativity theory so as to encompass more realistic nonideal measurements. It is argued that this generalization favours an empiricist interpretation of the mathematical formalisms over a realist one.

governed by Newtonian laws. In standard quantum mechanics only the wave function or the results of measurements exist, and to answer the question of how the classical world can be part of the quantum world is a rather formidable task. However, this is not the case for Bohmian mechanics, which, like classical mechanics, is a theory about real objects. In Bohmian terms, the problem of the classical limit becomes very simple: when do the Bohmian trajectories look Newtonian?

On Mass Problem in Relativistic Mechanics and Gravitational Physics Anatoli Vankov (dated 12.16.2003, e-mail: anatolivankov@hotmail.com) The proper mass of a test particle in General Relativity Theory (GRT) is a rest mass, so it is considered principally constant, just as in Kinematics of Special Relativity Theory (SRT). One may think that the same is true in SRT Mechanics (Dynamics). We found that a proper mass change occurs under a force action that is, during a transition from one inertial reference frame to another. The proper mass constancy in SRT Mechanics is, in fact, a weak field approximation leading to the Newtonian limit. We show that a variability of the proper mass is a fundamental physical phenomenon. It becomes especially important under strong field conditions, therefore, for understanding of the so-called self-energy divergence. The problem was seemingly overcome with help of the known renormalization procedure in Electrodynamics but not in gravitational field theory. GRT was shown to be nonrenormalizable. Our analysis of the SRT mass-energy concept showed that, after the proper mass variation was taken into account in SRT Mechanics equations, arguments for an exclusion of the gravity phenomenon from the SRT domain fell away. Moreover, this approach resulted in principal elimination of the gravitational divergence problem. Another new result concerned the speed of light. The conclusion was that the speed of light is not a fundamental physical constant: it is a physical quantity determined by a gravitational potential and has a cosmological meaning. In spite of radically different physical interpretation, the alternative approach to the gravitational problem gives an adequate description of “weak-field” gravitational experiments as GRT does: a numerical difference from GRT predictions is not meaningful. However, the difference in predictions progressively rises with field strength and an energy increase. One particular result concerns a behavior of a massive particle being in free fall in a gravitational field. In GRT, both a free particle and a photon, when approaching a gravitational center, tend to slow down, the particle speed being always less then the photon speed. In the SRT approach, the photon similarly slows down but not the particle. If so, superluminal particles exist. This is a new physical phenomenon, which may be called a gravitational refraction. We propose the experiment on the detection of superluminal particles in high-energy cosmic rays. It should be considered a new relativistic test having a falsifying power in a strong-field domain. This work is mainly conceptual. The purpose is to present in a simple form for a wide physical community some results of our study of Relativistic Mechanics, in which a source of a gravitational field is the proper mass. The main conclusion is that the development of the SRT-based divergence-free gravitation field theory is possible. PACS 04.80.Cc Key words: 1. General relativity

This paper addresses a relatively common scientific (as opposed to philosophical) conception of intertheoretic reduction between physical theories. This is the sense of reduction in which one (typically newer and more refined) theory is said to reduce to another (typically older and coarser) theory in the limit as some small parameter tends to zero. Three examples of such reductions are discussed: First, the reduction of Special Relativity (SR) to Newtonian Mechanics (NM) as (v/c)20; second, the reduction of wave optics to geometrical optics as 0; and third, the reduction of Quantum Mechanics (QM) to Classical Mechanics (CM) as0. I argue for the following two claims. First, the case of SR reducing to NM is an instance of a genuine reductive relationship while the latter two cases are not. The reason for this concerns the nature of the limiting relationships between the theory pairs. In the SR/NM case, it is possible to consider SR as a regular perturbation of NM; whereas in the cases of wave and geometrical optics and QM/CM, the perturbation problem is singular. The second claim I wish to support is that as a result of the singular nature of the limits between these theory pairs, it is reasonable to maintain that third theories exist describing the asymptotic limiting domains. In the optics case, such a theory has been called catastrophe optics. In the QM/CM case, it is semiclassical mechanics. Aspects of both theories are discussed in some detail.

Radically reoriented presentation of Einstein's Special Theory and one of most valuable popular accounts available derives relativity from Newtonian ideas, ...

Norton (2003 and 2006) has recently argued that causation is merely a useful folk concept and that it fails to hold for some simple systems even in the supposed paradigm case of a causal physical theory – namely Newtonian mechanics. The purpose of this article is to argue against this devaluation of causality in physics. My main argument is that Norton’s alleged counterexample to causality (and determinism) within standard Newtonian physics fails to obey what I shall call the causal core of Newtonian mechanics. In particular, I argue, Norton’s example is not in conformity with Newton’s first law. Moreover, Norton’s reformulation of this first law (in an instantaneous form) seems insufficient as a replacement for the original version since the notion of inertial frames in the resulting reformulated theory lacks a physical justification, and since an intelligible notion of time in Newtonian mechanics appears to be closely tied to Newton’s first law in its standard form. I will finally suggest how, given a plausible relationist account of time, the causal core of Newtonian mechanics may play a central role also in relativity and quantum theory.

We consider the following question within both Newtonian physics and relativity theory. "Given two point particles X and Y, if Y is rotating relative to X, does it follow that X is rotating relative to Y?" As it stands the question is ambiguous. We discuss one way to make it precise and show that, on that reading at least, the answers given by the two theories are radically different. The relation of relative orbital rotation turns out to be symmetric in Newtonian physics, but not in relativity theory.

The advent of the special theory of relativity in 1905 brought many problems for the physics community. One, it seemed, would not be a great source of trouble. It was the problem of reconciling Newtonian gravitation theory with the new theory of space and time. Indeed it seemed that Newtonian theory could be rendered compatible with special relativity by any number of small modifications, each of which would be unlikely to lead to any significant deviations from the empirically testable conse- 1 quences of Newtonian theory. Einstein’s response to this problem is now legend. He decided almost immediately to abandon the search for a Lorentz covariant gravitation theory, for he had failed to construct such a theory that was compatible with the equality of inertial and gravitational mass. Positing what he later called the principle of equivalence, he decided that gravitation theory held the key to repairing what he perceived as the defect of the special theory of relativity—its relativity principle..

Comprehensive coverage of the special theory (frames of reference, Lorentz transformation, relativistic mechanics of mass points, more), the general theory ...

Are Classical Mechanics and the Special Theory of Relativity Commensurable? In its first part, this paper shows why a recently made attempt to reduce the special theory of relativity to Newtonian kinematics is bound to fail. In the second part, we propose a differentiated notion of incommensurability which enables us to amend the contention that the special theory of relatively and Newtonian kinematics are "incommensurable".