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At least 451 records · Page 25Linked to original sources
arXiv2014

Uffenbach's "Zeitweiser" published 1598

In the year 1598 Philipp Uffenbach published a printed diptych sundial, which is a forerunner of Franz Ritters horizantal sundial. Uffenbach's sundial contains apart from the usual information on a sundial ascending signs of the zodiac, several brigthest stars, an almucantar and most important the oldest gnomonic world map known so far. The sundial is constructed for the polar height of 50 1/6 degrees, the height of Frankfurt/Main the town of his citizenship.

physics.hist-ph↗
arXiv2014

On the Superposition and Elastic Recoil of Electromagnetic Waves

Superposition demands that a linear combination of solutions to an electromagnetic problem also be a solution. This paper analyzes some very simple problems: the constructive and destructive interferences of short impulse voltage and current waves along an ideal free-space transmission line. When voltage waves constructively interfere, the superposition has twice the electrical energy of the individual waveforms because current goes to zero, converting magnetic to electrical energy. When voltage waves destructively interfere, the superposition has no electrical energy because it transforms to magnetic energy. Although the impedance of the individual waves is that of free space, a superposition of waves may exhibit arbitrary impedance. Further, interferences of identical waveforms allow no energy transfer between opposite ends of a transmission line. The waves appear to recoil elastically one from another. Although alternate interpretations are possible, these appear less likely. Similar phenomenology arises in waves of arbitrary shape and those propagating in free space as well. We may also interpret this behavior as each wave reflecting from the impedance variations the superposition imparts on free space. This work has practical implications to quantum mechanics, field diversity antenna systems, and near-field electromagnetic ranging.

physics.class-ph↗
arXiv2014

Analysis of Free Will and Determinism in Physics

It is considered the study of determinism in the theories of physics. Based on fundamental postulates of physics, it is proved that the evolution of the universe is univocally determined, proving ultimately that free will does not exist. In addition, it is presented some contradictions and weaknesses of quantum mechanics, suggesting paradoxes in the theory. It is also analyzed some consequences of the postulates in justice and ethics.

physics.gen-ph↗
arXiv2014

Relativistic Lighthouses: The Role of the Binary Pulsar in proving the existence of Gravitational Waves

This paper discusses the role of the discovery and analysis of the first binary pulsar in settling the long-running quadrupole formula controversy over the status of gravitational waves as a prediction of general relativity. It also discusses how we should understand the resolution of this controversy in the context of the so-called science wars. In other words it discusses whether concepts such as interpretive flexibility and the experimenters' regress can shed light on what can also be seen as a classical confirmation of realist expectations, in which a theoretical controversy is settled by a conclusive experiment.

physics.hist-ph↗
arXiv2014

To Principles of Quantum Mechanics Development

New insight to the principles of the quantum physics development is given. The correct ways for the construction of new versions of quantum mechanics on the second main postulate base are discussed. The conclusion on the status of the second main postulate is given. Its formulation in all textbooks has to be represented in the form of statement, since the hypothesis of Schrödinger on the existance of the field scalar function, being to be observable quantity, just charge density, is strictly proved for the case of EM-field, the role of which is argued to be decisive for the dynamics of the atomic systems. It is shown, that the field scalar function, being to be the function the only of coordinates and time, actually describes the state of the system. The second main postulate in Schrödinger formulation is mathematically strictly grounded, but in the popular probabilistic form used in modern textbooks on quantum theory it cannot be proved. The probabilistic theatise, proposed by Born is true in a number of special cases, quite correctly indicated by Dirac. The possible ways of the development of quantum theory, based on clear understanding of the origin of corpuscular-wave dualism are analysed.

physics.hist-ph↗
arXiv2014

Truth problem in the context of interpretations of quantum logic

The paper defends the thesis that analysis of truth problem in the context of interpretations of quantum logic allows to reveal the prospect of elicitation of specifics of the relations between quantum mechanics and quantum logic in a context of modal expansions of quantum logic. It is found the way for solution of the problem of detection of features of creation of quantum-mechanical researches as a single case of semantics of "the possible worlds". Studies in the field of logic foundation of quantum physics receive the status of "possible quantum mechanics". Therefore they can be presented not simply as "truth" and "false" distinction within judgments about the physical phenomena but also as display logically possible and (or) impossible, necessary and (or) casual constructions of physical sciences.

physics.hist-ph↗
arXiv2017

The wave equation in the birth of spacetime symmetries

In 1887 Voigt published a paper dedicated to the Doppler effect in which he demanded form invariance to the wave equation in inertial frames and obtained a set of spacetime transformations now known as the Voigt transformations. In 1905 Poincaré showed that the wave equation was also invariant under the Lorentz transformations. Voigt and Lorentz transformations are then closely related, but this relation is not widely known in the standard literature. In this paper we derive the Lorentz transformations from the invariance of the D'Alembert operator $\big(\Box^{2}=\Box'^{2}\big)$ and the Voigt transformations from the conformal invariance of the D'Alembert operator $\big(\Box^{2}=(1/γ^2)\Box'^{2},$ where $γ=1/\sqrt{1-v^2/c^2}\big).$ The homogeneous scalar wave equation is then invariant under the Lorentz transformations and conformally invariant under the Voigt transformations. We suggest a presentation of special relativity in which the Voigt transformations are commented after discussing the Galilean transformations but before presenting the Lorentz transformations.

physics.hist-ph↗
arXiv2014

Consciousness and the Physical World

Edited proceedings of an interdisciplinary symposium on consciousness held at the University of Cambridge in January 1978. The purpose of the Cambridge conference was to encourage distinguished scientists to express their views on the relationship of conscious experience to the physical world.

physics.gen-ph↗
arXiv2014

Jayant Vishnu Narlikar

An essay on Jyant Narlikar in the Living Legends of Indian Science series of the journal Current Science.

physics.hist-ph↗
arXiv2014

On the Observations of the Sun in Polynesia

The role of the Polynesian sun god Tagaloa has been studied. The Polynesian characters Maui-tikitiki, Tane and Tiki were related to the sun as well. The solar data of Easter Island are essential indeed. The rongorongo text on the Santiago staff about the solar eclipse of December 20, 1805 A.D. has been decoded. The Mataveri calendar was probably incised on a rock in 1775 A.D. So, a central event during the bird-man festval was the day of vernal equinox. The priests-astronomers watched not only the sun and the moon, but also some stars of the zodiacal constellations and other bright stars.

physics.hist-ph↗
arXiv2014

Diplomacy and science in the context of World War II: Arthur Compton's 1941 trip to Brazil

Historical literature has traced US efforts to bring Latin American countries over to the side of the Allies in WWII. Following a period of hesitation and negotiation with the US and Germany, the Brazilian government aligned itself with the US. What remains virtually unknown is the involvement of scientists in these diplomatic arrangements. Recently unearthed material has shown that Arthur Compton's 1941 trip to a scientific conference on cosmic rays in Brazil was linked to efforts led by the Office for Inter-American Affairs under Nelson Rockefeller. For the Brazilian physicists, who, under the leadership of Gleb Wataghin, had excelled in this area of research during the late 1930s, science was a strong motivation for the visit; it was not, however, devoid of political connotations and professional interests.

physics.hist-ph↗
arXiv2014

Galileo in early modern Denmark, 1600-1650

The scientific revolution in the first half of the seventeenth century, pioneered by figures such as Harvey, Galileo, Gassendi, Kepler and Descartes, was disseminated to the northernmost countries in Europe with considerable delay. In this essay I examine how and when Galileo's new ideas in physics and astronomy became known in Denmark, and I compare the reception with the one in Sweden. It turns out that Galileo was almost exclusively known for his sensational use of the telescope to unravel the secrets of the heavens, meaning that he was predominantly seen as an astronomical innovator and advocate of the Copernican world system. Danish astronomy at the time was however based on Tycho Brahe's view of the universe and therefore hostile to Copernican and, by implication, Galilean cosmology. Although Galileo's telescope attracted much attention, it took about thirty years until a Danish astronomer actually used the instrument for observations. By the 1640s Galileo was generally admired for his astronomical discoveries, but no one in Denmark drew the consequence that the dogma of the central Earth, a fundamental feature of the Tychonian world picture, was therefore incorrect.

physics.hist-ph↗
arXiv2014

The representations of the sky among the Tomaraho

The Tomárãho is an ethnic group of the Paraguayan Chaco who maintained close contact with nature and developed original ways of explaining and understanding it. This article presents the first results of an interdisciplinary project seeking to provide a detailed analysis of different astronomical elements in the imagined sky of the Tomárãho.

physics.hist-ph↗
arXiv2016

The Function of the Second Postulate in Special Relativity

Many authors noted that the principle of relativity, together with space-time symmetries, suffices to derive Lorentz-like coordinate transformations between inertial frames. These contain a free parameter, $k$, (equal to $c^{-2}$ in special relativity) which is usually claimed to be empirically determinable, so that special relativity does not need the postulate of constancy of the speed of light. I analyze this claim and find that all methods destined to measure $k$ fail without further assumptions, similar to the second postulate. Specifically, measuring $k$ requires a signal that travels identically in opposite directions (this is unrelated to the conventionality of synchronization, as the one-postulate program implicitly selects the standard synchronization convention). Positing such a property about light is logically weaker than Einstein's second postulate but suffices to recover special relativity in full.

physics.hist-ph↗
arXiv2014

Classical Black Holes Are Hot

In the early 1970s it is was realized that there is a striking formal analogy between the Laws of black-hole mechanics and the Laws of classical thermodynamics. Before the discovery of Hawking radiation, however, it was generally thought that the analogy was only formal, and did not reflect a deep connection between gravitational and thermodynamical phenomena. It is still commonly held that the surface gravity of a stationary black hole can be construed as a true physical temperature and its area as a true entropy only when quantum effects are taken into account; in the context of classical general relativity alone, one cannot cogently construe them so. Does the use of quantum field theory in curved spacetime offer the only hope for taking the analogy seriously? I think the answer is `no'. To attempt to justify that answer, I shall begin by arguing that the standard argument to the contrary is not physically well founded, and in any event begs the question. Looking at the various ways that the ideas of "temperature" and "entropy" enter classical thermodynamics then will suggest arguments that, I claim, show the analogy between classical black-hole mechanics and classical thermodynamics should be taken more seriously, without the need to rely on or invoke quantum mechanics. In particular, I construct an analogue of a Carnot cycle in which a black hole "couples" with an ordinary thermodynamical system in such a way that its surface gravity plays the role of temperature and its area that of entropy. Thus, the connection between classical general relativity and classical thermodynamics on their own is already deep and physically significant, independent of quantum mechanics.

gr-qc↗
arXiv2014

Origins of Radio Astronomy at the Tata Institute of Fundamental Research and the Role of J.L. Pawsey

I will discuss the interactions of a number of individuals that played major roles in the formation of radio astronomy in India in the period 1952-1962, particularly Dr. Joseph L. Pawsey. The story began in 1953-1954: Pawsey brought Govind Swarup to Australia as a Colombo Fellow in 1953, where he worked with Christiansen, Mills, Wild and Bolton. Later, Swarup went to Stanford where he completed a PhD with Ron Bracewell working on the new Solar Microwave Spectroheliograph. In the era 1960-1963, with the encouragement of Pawsey, several colleagues in Australia and Bracewell, discussions began among a number of Indian colleagues to form a radio astronomy group in India. The main players were G. Swarup, T.K. Menon, M.R. Kundu and T. Krishnan. Homi J. Bhabha, the Director of TIFR, made the decisive offer to this group to start a radio astronomy project in early 1962. Swarup joined TIFR in early April 1963. Many factors contributed to the successful formation of the new group: international networking among scientists of several generations, rapid decisions by Bhabha and the readiness to take chances in choosing promising, young, energetic scientists.In December 2013, we have celebrated 50 years of ground breaking research by the TIFR radio astronomers as well as the outstanding decade of research with the GMRT- the Giant Metrewave Radio Telescope. Govind Swarup has provided the inspiration and leadership for this remarkable achievement.

physics.hist-ph↗
arXiv2014

Astrosociology: Interviews about an infinite universe

If the universe is infinite now it has always been infinite. This is the opinion of many astronomers today as can be concluded from the following series of interviews, but the opinions differ much more than I had expected. Many astronomers do not have a clear opinion on this matter. Others have a clear opinion, but very different from the majority. Detailed arguments by two experts on general relativity are also included. Observations show that the universe is flat, i.e. the curvature is zero within the small uncertainty of measurements. This implies an infinite universe, though most probably we will never know that for certain. For comparison with the recent interviews, opinions during the past 2300 years since Aristotle about the universe being finite or infinite have been collected from literature, and it appears that the scientists often had quite definite opinions. \c{opyright} Anita Publications. All rights reserved.

physics.hist-ph↗