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At least 235 records · Page 13Linked to original sources
arXiv2013

Reichenbach's Transcendental Probability

The aim of this article is twofold. First, we shall review and analyse the Neo-Kantian justification for the application of probabilistic concepts in physics that was defended by Hans Reichenbach early in his career, notably in his dissertation of 1916. At first sight this Kantian approach seems to contrast sharply with Reichenbach's later logical positivist, frequentist viewpoint. But, and this is our second goal, we shall attempt to show that there is an underlying continuity in Reichenbach's thought: typical features of his early Kantian conceptions can still be recognized in his later work.

physics.hist-ph↗
arXiv2013

The Paraná Ra'anga expedition

Paraná Ra'anga (the image of Paraná, in Guaraní) is the name of a cultural and scientific expedition that traveled the rivers: Río de la Plata, Paraná and Paraguay, from Buenos Aires to Asunción, during March 2010. The project brought together some forty scientists and artists from three countries in a slow and enriching cruise, putting in active contact actors from different backgrounds and disciplines -which usually run separately- in the framework of an unusual space-time experience. The project recovers the historical tradition of the trip as an instrument of knowledge and collaboration between the arts and sciences, necessary to build new ways of seeing and understanding the river and its banks. This article reports on the motivations of this project and its projection.

physics.pop-ph↗
arXiv2013

Yet Another Snapshot of Foundational Attitudes Toward Quantum Mechanics

A survey probing respondents' views on various foundational issues in quantum mechanics was recently created by Schlosshauer, Kofler, and Zeilinger [arXiv:1301.1069] and then given to 33 participants at a quantum foundations conference. Here we report the results of giving this same survey to the attendees at another recent quantum foundations conference. While it is rather difficult to conclude anything of scientific significance from the poll, the results do strongly suggest several interesting cultural facts -- for example, that there exist, within the broad field of "quantum foundations", sub-communities with quite different views, and that (relatedly) there is probably even significantly more controversy about several fundamental issues than the already-significant amount revealed in the earlier poll.

quant-ph↗
arXiv2013

Classical Electrodynamics and Absolute Simultaneity

Maxwell's equations and the Lorentz force density are expressed using an alternative simultaneity gauge. As a result, they describe electrodynamics for an observer travelling with a constant velocity through an isotropic medium. If desired, one may regard the isotropic medium as an absolute space. An observer at rest in the medium may be referred to as a preferred observer. The medium appears electrically polarized to the moving observer. Such an observer regards the speed of light as anisotropic by convention while sharing absolute simultaneity relations with the preferred observer.

physics.hist-ph↗
arXiv2013

Einstein, the reality of space, and the action-reaction principle

Einstein regarded as one of the triumphs of his 1915 theory of gravity --- the general theory of relativity --- that it vindicated the action--reaction principle, while Newtonian mechanics as well as his 1905 special theory of relativity supposedly violated it. In this paper we examine why Einstein came to emphasise this position several years after the development of general relativity. Several key considerations are relevant to the story: the connection Einstein originally saw between Mach's analysis of inertia and both the equivalence principle and the principle of general covariance, the waning of Mach's influence owing to de Sitter's 1917 results, and Einstein's detailed correspondence with Moritz Schlick in 1920.

physics.hist-ph↗
arXiv2013

Inferential vs. Dynamical Conceptions of Physics

I contrast two possible attitudes towards a given branch of physics: as inferential (i.e., as concerned with an agent's ability to make predictions given finite information), and as dynamical (i.e., as concerned with the dynamical equations governing particular degrees of freedom). I contrast these attitudes in classical statistical mechanics, in quantum mechanics, and in quantum statistical mechanics; in this last case, I argue that the quantum-mechanical and statistical-mechanical aspects of the question become inseparable. Along the way various foundational issues in statistical and quantum physics are (hopefully!) illuminated.

quant-ph↗
arXiv2013

A possible role of sunrise/sunset azimuth in the planning of ancient Chinese towns

In the planning of some Chinese towns we can see an evident orientation with the cardinal north-south direction. However, other features reveal a possible orientation with the sunrise/sunset azimuth on solstices too, as in the case of Shangdu (Xanadu), the summer capital of Kublai Khan. Here we discuss some other examples of a possible solar orientation in the planning of ancient towns. We will analyze the plans of Xi'an, Khanbalik and Dali.

physics.hist-ph↗
arXiv2013

Physical Relativism as an Interpretation of Existence

Despite the success of modern physics in formulating mathematical theories that can predict the outcome of quantum-scale experiments, the physical interpretations of these theories remain controversial. In this manuscript, we propose a new interpretation of existence that we call physical relativism. Under physical relativism, the difference between mathematical existence and physical existence is clarified, and Wheeler's `it from bit' viewpoint can be objectively evaluated. In addition, physical relativism provides a simple answer to the question of why the universe exists at all, and permits us to derive the maximally biophilic principle, a generalization of the anthropic principle that ascribes high prior likelihood to the observation of a universe with simple physical laws supporting the overall concepts of time, space and the emergent evolution of life.

physics.hist-ph↗
arXiv2013

Geometrie und Astronomie im Stadtplan des hethitischen Sarissa

The Hittite city Sarissa was founded in the 16th century BC and has been systematically constructed. The city gates and the bigger public buildings were arranged at about 45° relative to the cardinal directions. However, one of the temples features a remarkable deviation from this general orientation. The following analysis shows that both, the general orientation of the public buildings and the deviation of one of the temples are related to astronomical observations, particularly to the course of the sun, and maybe also to some special points of the course of the Venus.

physics.hist-ph↗
arXiv2013

Prehistoric sanctuaries in Daunia

Daunia is a region in northern Apulia with many interesting archaeological sites, particularly of the Neolithic and Bronze Age. Beginning from the fifth millennium BC, the farmers living in the wide plain of Daunia dug hypogea and holes in sites that could be considered prehistoric sanctuaries. The characteristics of the rows of holes indicate a ritual use, and the archaeologists tend to exclude other applications, such as post holes and cultivations. The rows have possibly an astronomical orientation, and in the sanctuary discovered near Ordona, some stars of the Centaurus-Crux group (may be alpha Centauri itself) could have been used as targets. In past centuries, astronomers and scholars have remarked this spectacular region of the sky, and its possible relevance for the ancient civilizations was pointed out for example by G.V. Schiaparelli in 1903. In his work on the astronomy in the Old Testament, he mentioned in particular the observations of the astronomer W.S. Jacob and of other scholars. It would be probably worth to make simulations in order to reproduce the 'Jacob effect', that is the diffused light (a sort of faint twilight) produced by such very rich stellar region of the sky.

physics.hist-ph↗
arXiv2013

Einstein's "Prague field-equation" -- another perspective

I reconsider Einstein's 1912 "Prague-Theory" of static gravity based on a scalar field obeying a non-linear field equation. I point out that this equation follows from the self-consistent implementation of the principle that all energies source the gravitational field according to E=m(c-squared). This makes it an interesting toy-model for the "flat-space approach" to General Relativity, as pioneered by Kraichnan and later Feynman. Solutions modelling stars show features familiar from GR, e.g., Buchdahl-like inequalities. The relation to full GR is also discussed. This lends this toy theory also some pedagogical significance.

gr-qc↗
arXiv2013

Majorana, Pauling and the quantum theory of the chemical bond

We discuss in detail very little known results obtained by Majorana as early as 1931, regarding the quantum theory of the chemical bond in homopolar molecules, based on the key concept of exchange interaction. After a brief historical overview of the quantum homopolar valence theory, we address the intriguing issues of the formation of the helium molecular ion, He2+, and of the accurate description of the hydrogen molecule, H2. For the first case, the group theory-inspired approach used by Majorana is contrasted with that more known followed by Pauling (and published few months after that of Majorana), while for the second case we focus on his proposal concerning the possible existence of ionic structures in homopolar compounds, just as in the hydrogen molecule. The novelty and relevance of Majorana's results in the modern research on molecular and chemical physics is emphasized as well.

physics.hist-ph↗
arXiv2013

Bernard Yarnton Mills 1920-2011

Bernie Mills is remembered globally as an influential pioneer in the evolving field of radio astronomy. His contributions with the 'Mills Cross' at the CSIRO Division of Radiophysics and later at the University of Sydney's School of Physics and the development of the Molonglo Observatory Synthesis Telescope (MOST) were widely recognised as astronomy evolved in the years 1948-1985 and radio astronomy changed the viewpoint of the astronomer as a host of new objects were discovered.

physics.hist-ph↗
arXiv2013

Three Merry Roads to T-Violation

This paper is a tour of how the laws of nature can distinguish between the past and the future, or be T-violating. I argue that, in terms of the basic argumentative structure, there are really just three approaches currently being explored. I show how each is characterized by a symmetry principle, which provides a template for detecting T-violating laws even without knowing the laws of physics themselves. Each approach is illustrated with an example, and the prospects of each are considered in extensions of particle physics beyond the standard model.

math-ph↗
arXiv2013

The Recurrent Nova T CrB Did Not Erupt in 1842

The recurrent nova T CrB was one of the first well observed nova eruptions in 1866, and 80 years later it erupted again in 1946. Just after the 1866 eruption, Sir John Herschel reported to the Monthly Notices that he had seen the same star in his naked-eye charting of the sky on 1842 June 9, implying that there was a prior eruption 24 years earlier. Unfortunately, the chart in the Monthly Notices was ambiguous and misleading, so it has long been unclear whether T CrB did indeed have an eruption in 1842. To resolve this, I have searched the various archives with Herschel material, and have found his original correspondence. In one letter from 1866 to William Huggins, Herschel enclosed his own copy of his original observations, and with this all the ambiguities are resolved. It turns out that Herschel's indicated star was at the same position as a steady background star (BD+25°3020, V=7.06, G8V) and not that of T CrB, and Herschel regularly was seeing stars as faint as V=7.5 mag because he was using an opera glass. With this, there is no evidence for a T CrB eruption in 1842.

astro-ph.SR↗
arXiv2015

Physical Determination of the Action

The objective is a foundation of physics from the operationalization of its basic observables. We begin with classical and relativistic kinematics. Seizing on a programmatic proposal by Heinrich Hertz we arrive via quantification of energy-momentum at the equations of motion and the action functional. Finally we present a relativistic revision of energy, momentum and inertial mass. The goal is not primarily to change or improve the mathematical structure of mechanics, but to gain a deeper physical understanding of mechanics like Einstein with his gedanken experiments on relativistic kinematics. Starting from undisputed measurement operations and natural principles the mathematical formalism is only created and thus shown in a new light. This work is in the same context as current efforts to the "foundation of quantum mechanics", just with respect to the interpretation of the classical and relativistic calculuses.

physics.hist-ph↗
arXiv2013

Quantum Will: Determinism meets Quantum Mechanics

We present a brief non-technical introduction to the standing discussion on the relation between Quantum Mechanics and Determinism. Quantum Mechanics inherent randomness in the measurement process is sometimes presented as a door to explain free will. We argue against this interpretation. The possibility that Quantum Mechanics provides just an effective description of Nature which is only valid at our low-energy scales is also discussed.

quant-ph↗