Local versions of the (special) principle of relativity say that if the same type of experiment is conducted in two isolated, unaccelerated laboratories, then the outcomes of those experiments must be the same. Global versions of the principle say that if you take a physically possible world and boost the entire material content of that world, you get another physically possible world. Some authors say that the local and the global principles are logically independent, and that the local version is (...) more important. These authors are wrong. I argue that the global version entails the local version, and discuss why a counterexample to this entailment offered by Tim Budden fails. (shrink)

Recently a suggestion has been made that standard textbook representations of hypersurfaces of simultaneity for the travelling twin in the twin 'paradox' are incorrect. This suggestion is false: the standard textbooks are in agreement with a proper understanding of the relativity of simultaneity.

Einstein's argument on the relativity of simultaneity itself is the first result of the special theory of relativity. This argument is reflected in the structure and functioning of the physical world. The arbitrary nature of the decision regarding the particular inertial reference frame from which the argument on the relativity of simultaneity begins is discussed. It is this arbitrary, or freely made, decision that is the basis for the significance of the argument of the relativity of simultaneity itself on the (...) structure and functioning of the physical world. The same concrete circumstances in the physical world can support either direction in the argument on the relativity of simultaneity, as well as other results, in the special theory. There are different sets of results in the physical world associated with the choice in direction that is made, for example as concerns the temporal durations of occurrences or the spatial lengths of existents in these inertial reference frames. Experiments testing the equations derived in the special theory that relate the temporal durations of occurrences or the spatial lengths of physical existents in inertial reference frames in uniform motion relative to one another generally have not tested predictions with both of the two inertial reference frames considered, in separate scenarios, the "stationary" reference frame. It is proposed that empirical tests in two directions be developed and conducted. If empirical results from such tests support the predictions of the special theory, these empirical results would support the thesis that there is a cognitive factor in Einstein's argument on the relativity of simultaneity that affects results derived in the special theory concerning the physical world. One such test is proposed. (shrink)

The lowest order processes described within quantum electrodynamics are free from the problems of infinites in the theory, and can be dealt with disregarding the need for charge and mass renormalization. This might indicate that the space-time description of these processes is not only consistent but also could give a privileged insight to the functioning of models provided by the theory. The Møller scattering is as R. P. Feynman considered, a prototype for the development of his rules of quantum electrodynamics (...) and his overall space-time approach. The study of Møller scattering might then provide the must straightforward way to the understanding of the space-time description of interactions provide by quantum electrodynamics. This method is much less powerful than might be expected at first, pointing to the intrinsic limitations of the theory in what regards the modelling of the temporality in interaction processes. (shrink)

When addressing the notion of proper time in the theory of relativity, it is usually taken for granted that the time read by an accelerated clock is given by the Minkowski proper time. However, there are authors like Harvey Brown that consider necessary an extra assumption to arrive at this result, the so-called clock hypothesis. In opposition to Brown, Richard TW Arthur takes the clock hypothesis to be already implicit in the theory. In this paper I will present a view (...) different from these authors by recovering Einstein’s notion of natural clock and showing its relevance to the debate. (shrink)