Eddington and Uncertainty

Arthur Stanley Eddington (1882-1944) is acknowledged to be one of the greatest astrophysicists of the twentieth century, yet his reputation suffered in the 1930s when he embarked on a quest to develop a unified theory of gravity and quantum mechanics. His attempt ultimately proved to be fruitless and was regarded by many physicists as misguided. I will show, however, that Eddingtons work was not so outlandish. His theory applied quantum-mechanical uncertainty to the reference frames of relativity and actually foreshadowed several later results. His philosophy regarding determinism and uncertainty also was quite orthodox at the time. I first review Eddingtons life and philosophy and then discuss his work within the context of his search for a theory of quantum gravity.     

Quirino Majorana’s Experiments on the Speed of Light and Gravitational Absorption

Quirino Majorana (1871–1957) was an outstanding Italian experimental physicist who investigated a wide range of phenomena during his long career in Rome,Turin, and Bologna. We focus on his experiments in Turin during 1916–1921 and in Bologna during 1921–1934 to test the validity of Albert Einstein’s postulate on the constancy of the speed of light and to detect gravitational absorption. These experiments required extraordinary skill, patience, and dedication, and all of them confirmed Einstein’s postulate and Isaac Newton’s law of universal gravitation to high precision. Had they not done so, Majorana’s fame among historians and physicists no doubt would be much greater than it is today. Giorgio Dragoni is Professor of History of Physics at the University of Bologna. Giulio Maltese is a Roman member of the Italian Society for the History of Physics and Astronomy. Luisa Atti is a Bolognese member of the Association for the Teaching of Physics.     

Astrophysically significant solutions of the Einstein and Einstein-Maxwell equations from the Laplace’s seed

The stationary solutions given by Amenedo and Manko generated from known solutions of Laplace’s equation as seed have been generalised to include the electromagnetic field. Further, the exterior solution of an axially symmetric rotating body with higher multipole moments and a solution corresponding to a Kerr object embedded in a gravitational field are given. We also give a method for constructing stationary vacuum solutions from static magnetovac solutions and vice versa and discuss a specific application of this method.     

Peter Bergmann:The Education of a Physicist

I explore the early life and contributions of Peter Bergmann (1915–2002), focusing on his family background, education, and ideas. I examine how Bergmann’s formative years were shaped by the outspoken influence of his mother, a leading educational reformer; the distinguished reputation of his father, a renowned materials chemist; and his cherished hope of working with Albert Einstein (1879–1955), to whom he eventually became an assistant. Inspired by these and other notable thinkers, Bergmann became an exemplary organizer, educator, and mentor in the fields of general relativity and quantum gravity.     

利用爱因斯坦转盘推求中心引力场中的光频红移--在普通物理教学中讲解等效原理的一种尝试

通过球对称引力场与爱因斯坦转盘上的惯性离心力场的对比，利用强等效原理导出光频的引力红移。     

想象力比知识更重要——从相对论的起源谈起

文章介绍了爱因斯坦相对论的起源,并对学校教育进行了思考.相对论起源于爱因斯坦对光速问题与相对性问题的研究,从相对论的起源与建立不难发现,其中最具关键性作用的并非人们的既有知识,而是爱因斯坦超乎寻常的想象力.相对论的起源充分证明,在推动科学发展的知识创新活动中,想象力与创新精神比知识更重要.人的知识是有限的,然而想象力是无限的,想象力与创新精神是知识进化的源泉.学校教育的目的不仅在于传授知识,更重要的在于激发人的想象力与培养人的创新精神.     

The Calculations that Gave Einstein “Heart Palpitations”

In what follows, I reply to the preceding article by Michel Janssen and Robert Schulmann, which itself was a response to my article on One month in the history of the discovery of general relativity theory, published in the February 1998 issue of this journal. I stand by the historical analysis and conclusions presented in my original article.     

Algebraically special hypersurface-homogeneous Einstein spaces in general relativity

This paper illustrates the value of the Newman—Penrose complex null tetrad formalism by using it to obtain all algebraically special Einstein spaces admitting three-parameter groups of motions acting on timelike surfaces containing the repeated principal null direction. Taken together with earlier work, this enables us to give a complete list of Einstein spaces which are both algebraically special and hypersurface-homogeneous or homogeneous.     

Einstein,de Sitter and the beginning of relativistic cosmology in 1917

In 1917, both Einstein and de Sitter proposed a new interpretation of the universe as a whole: the structure of the universe could be described in terms of relativistic field equations. Their contributions marked the beginning of the modern scientific comprehension of the origin and evolution of the universe. Our aim is to propose a critical review paper, based on references in primary sources, on the formulation in 1917 of Einstein’s and de Sitter’s models of the universe, which represents a fundamental chapter in the history of relativistic Cosmology.     

狭义相对论中的重力及"潜水艇佯谬"

在狭义相对论范畴内,如果考虑地球周围较小区域内的动力学问题,可以用均匀质量密度的无限大平面产生的重力场替代地球的史瓦西场,从而得到较为简单的重力表达式.在此基础上可以很方便地解释所谓的"潜水艇佯谬".     

Smart Geodesic Tracing in GRworkbench

We have developed a new tool for numerical work in General Relativity: GRworkbench. We discuss how GRworkbench's implementation of a numerically-amenable analogue to Differential Geometry facilitates the development of robust and chart-independent numerical algorithms. We consider, as an example, geodesic tracing on two charts covering the exterior Schwarzschild space-time.     

Axially Symmetric Inflationary Universe in General Relativity

We have investigated a simple axially symmetric inflationary universe in the presence of mass less scalar field with a flat potential. To get an inflationary universe, we have considered a flat region in which potential V is constant. Some physical properties of the universe are also discussed.     

Free-Fall Non-Universality in Quantum Theory

The author shows by embodying the Einstein equivalence principle—local Poincaré invariance—and general covariance in quantum theory that wave-function spreading rules out the universality of free fall, that is, the free-fall trajectory of a quantum (test) particle depends on its internal properties. The author provides a quantitative estimate of the free-fall non-universality in terms of the Eötvös parameter, which turns out to be measurable in atom interferometry.     

Numerical Relativity and the Discovery of Gravitational Waves

Solving Einstein's equations precisely for strong‐field gravitational systems is essential to determining the full physics content of gravitational wave detections. Without these solutions it is not possible to infer precise values for initial and final‐state system parameters. Obtaining these solutions requires extensive numerical simulations, as Einstein's equations governing these systems are much too difficult to solve analytically. These difficulties arise principally from the curved, non‐linear nature of spacetime in general relativity. Developing the numerical capabilities needed to produce reliable, efficient calculations has required a Herculean 50‐year effort involving hundreds of researchers using sophisticated physical insight, algorithm development, computational technique, and computers that are a billion times more capable than they were in 1964 when computations were first attempted. The purpose of this review is to give an accessible overview for non‐experts of the major developments that have made such dramatic progress possible.     

Radial Quantization in Rotating Space–Times

We examine the time discontinuity in rotating space–times for which the topology of time is S¹. A kinematic restriction is enforced that requires the discontinuity to be an integral number of the periodicity of time. Quantized radii emerge for which the associated tangential velocities are less than the speed of light. Using the de Broglie relationship, we show that quantum theory may determine the periodicity of time. A rotating Kerr–Newman black hole and a rigidly rotating disk of dust are also considered; we find that the quantized radii do not lie in the regions that possess CTCs.     

Collapsing void in a spatially flat Robertson-Walker universe

We consider here a model of the spherical void (or its precursor) containing low density conducting fluid surrounded by a thick spherical shell of radiation embedded in a RobertsonWalker (RW) universe with flat space sections. The underdense region has a metric which is the special case of a solution given by Maiti [1] surrounded by Vaidya metric. We also assume the RW universe to be filled with a perfect fluid with a linear equation of state. The matching conditions indicate that if the time coordinate in each region is future directed then the underdense region appears to go on contracting to a comoving observer in the universe as the latter expands until it disappears. However, if the pressure in the RW universe vanishes, (approximately the present day condition), the underdense region remains static. We have also extended the space-time coordinates of Vaidya metric to the interior of the underdense region as well as the RW universe. It remains to be seen if the region having Vaidya metric disappears earlier than the interior or vice versa.