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In Einstein's Special Theory of Relativity, all observers measure the speed of light, $c$, to be the same. However, this refers to the round trip speed, where a clock at the origin times the outward and return trip of light reflecting off a…

General Relativity and Quantum Cosmology · Physics 2021-02-17 Geraint F. Lewis , Luke A. Barnes

Transformation rules for coordinates, velocities and accelerations in accelerated reference frames are derived. A generalized approach of the special relativity is taken for a basis. A 7-dimensional space including projections of velocity…

Classical Physics · Physics 2007-05-23 A. A. Ketsaris

Light experiences drag effects when it propagates through a moving medium. The study of light drag has provided foundational insights into light-matter interactions. While longitudinal drag has been extensively characterized, transverse…

Anomalous dispersion cannot occur in a transparent passive medium where electromagnetic radiation is being absorbed at all frequencies, as pointed out by Landau and Lifshitz. Here we show, both theoretically and experimentally, that…

Optics · Physics 2009-11-06 A. Dogariu , A. Kuzmich , L. J. Wang

A recent proposal to explore vacuum electrodynamics using the speed of propagation of an electromagnetic pulse through an ambient constant magnetic field is examined. It is argued that the proposal should be modified so that the background…

Mathematical Physics · Physics 2013-01-21 S. P. Flood , D. A. Burton

New varying speed of light (VSL) theories as alternatives to the inflationary model of the universe are discussed and evidence for a varying speed of light reviewed. Work linked with VSL but primarily concerned with deriving Planck's black…

General Physics · Physics 2007-05-23 Daniel J. Farrell , J. Dunning-Davies

Slow light in moving media reaches a paradoxical regime when the flow speed of the medium approaches the group velocity of light. Pulses can penetrate a region where a counter-propagating flow exceeds the group velocity. When the…

Quantum Physics · Physics 2009-11-06 J. Fiurasek , U. Leonhardt , R. Parentani

The mechanisms leading to a seemingly superluminal propagation of light in dispersive media are examined. The anomalous dispersion near an absorption line, involved in the first experiments displaying negative group velocity propagation, is…

Classical Physics · Physics 2007-05-23 Bruno Macke , Bernard Segard

All experiments attempting to verify the invariance of speed of light directly are based on two-way speed measurement. The challenge in one-way speed measurement, the requirement of spatially separated synchronised clocks, can be possibly…

Classical Physics · Physics 2013-03-20 Evan John Philip

Particle-antiparticle pairs are predicted by quantum field theory to appear as vacuum fluctuations. The model of the vacuum used here is postulated to have the following properties: To minimize the violation of conservation energy allowed…

Quantum Physics · Physics 2019-10-02 G. B. Mainland , Bernard Mulligan

We present a simple thought experiment in which a beam of light of a finite length (a light-pulse) enters a detection device that consists of a wave detector and a light bulb. We examine the experiment from the reference frame where the…

Physics Education · Physics 2007-05-23 Aleksandar Gjurchinovski

The nature of light, the existence of magnetism, the physical meaning of a vacuum are problems so deeply related to philosophy that they have been discussed for thousands of years. In this paper, we concentrate ourselves on a question that…

History and Philosophy of Physics · Physics 2023-03-28 Jonathan Agil , Rémy Battesti , Carlo Rizzo

In relativity and quantum field theory, the vacuum speed of light is assumed to be constant; the range of validity of general relativity is determined by the Planck length. However, there has been no convincing theory explaining the…

General Physics · Physics 2019-01-23 Christoph Köhn

Einstein's relativity theory appears to be very accurate, but at times equally puzzling. On the one hand, electromagnetic radiation must have zero rest mass in order to propagate at the speed of light, but on the other hand, since it…

History and Philosophy of Physics · Physics 2015-08-27 M. B. van der Mark , G. W. 't Hooft

Although special relativity limits the actual velocity of a particle to $c$, the velocity of light, the observed velocity need not be the same as the actual velocity as the observer is only aware of the position of a particle at the time in…

General Physics · Physics 2015-05-27 Austen Berlet , Dennis G. C. McKeon , Farrukh Chishtie , Martin Houde

Light-pulse atom interferometers serve as tools for high-precision metrology and are targeting measurements of relativistic effects. This development is facilitated by extended interrogation times and large-momentum-transfer techniques…

Quantum Physics · Physics 2025-05-06 Christian Niehof , Daniel Derr , Enno Giese

Method given for intuitively visualizing constancy of light speed. Using mass-energy equivalence, we can show with the help of simple thought experiments, that velocity time dilation and gravitational time dilation are a necessary…

General Physics · Physics 2014-08-29 Abdul Rouf

We propose a revised formulation of General Relativity for cosmological settings, in which the Einstein constant varies with the energy density of the Universe. We demonstrate that this modification has only phenomenological impact of…

General Relativity and Quantum Cosmology · Physics 2025-08-28 Giovanni Montani , Giulia Maniccia , Elisa Fazzari , Alessandro Melchiorri

An explanation for superluminal phenomena based on wave-particle duality of photons is suggested. A single photon may be regarded as a wave packet, whose spatial extension is its coherence volume. As a photon propagates as a wave train in…

Quantum Physics · Physics 2024-03-15 Hai-Long Zhao

Within an axiomatic framework of kinematics, we prove that the existence of faster than light particles is logically independent of Einstein's special theory of relativity. Consequently, it is consistent with the kinematics of special…

General Physics · Physics 2015-03-20 Gergely Székely