The Ritz theory of electromagnetism and optics is criticized in relation to the experimental evidence after the introduction of a simple and natural modification of the hypothesis concerning the velocity of radiation scattered by the electrons of a medium. It is argued that the theory is then in harmony with the electron theory of dispersion, accounts satisfactorily for aberration, the first-order Doppler effect from moving sources and interferometer experiments on binary stars. There is no evidence from binary stars which contradicts it. It is compatible with the second-order Doppler effect and possibly the Fizeau experiment since arguments are advanced which indicate that these phenomena depend essentially on the momentum and energy of radiation. Other phenomena are discussed. It is concluded that the best evidence against the theory comes from experiments on the lifetimes of fast mesons and the velocity of γ rays and light from moving sources. The justifications for the discussion are the desirability of having the experimental base of an important part of physics be as rigorous as possible, and the hope that it sharpens our understanding of existing evidence for special relativity and stimulates new and different experiments.

We report on the results of a strongly improved test of local Lorentz invariance, consisting of a search for an anisotropy of the resonance frequencies of electromagnetic cavities. The apparatus comprises two orthogonal standing-wave optical cavities interrogated by a laser, which were rotated approximately 175 000 times over the duration of 13 months. The measurements are interpreted as a search for an anisotropy of the speed of light, within the Robertson-Mansouri-Sexl (RMS) and the standard model extension (SME) photon sector test theories. We find no evidence for an isotropy violation at a 1sigma uncertainty level of 0.6 parts in 10(17) (RMS) and 2 parts in 10(17) for seven of eight coefficients of the SME.

The status of experimental tests of general relativity and of theoretical frameworks for analysing them are reviewed. Einstein's equivalence principle (EEP) is well supported by experiments such as the Eötvös experiment, tests of special relativity, and the gravitational redshift experiment. Future tests of EEP and of the inverse square law will search for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light defl ection the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected in an amount that agrees with general relativity to half a percent using the Hulse-Taylor binary pulsar, and new binary pulsar systems may yield further improvements. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible.

We report on a test of Lorentz invariance performed by comparing the resonance frequencies of one stationary optical resonator and one continuously rotating on a precision air bearing turntable. Special attention is paid to the control of rotation induced systematic effects. Within the photon sector of the standard model extension, we obtain improved limits on combinations of 8 parameters at a level of a few parts in 10(-16). For the previously least well known parameter we find [EQUATION: SEE TEXT]. Within the Robertson-Mansouri-Sexl test theory, our measurement restricts the isotropy violation parameter [EQUATION: SEE TEXT]. corresponding to an eightfold improvement with respect to previous nonrotating measurements.

High precision tests of the light speed constancy for all observers as a empirical basis of Special Relativity have continuously been among the goals of advanced experimental studies. Based on the Compton edge method proposed by us (Gurzadyan and Margarian in Phys Scr 53:513, 1996), a constraint on the one-way light speed isotropy and Lorentz invariance violation has been obtained at the dedicated GRAAL experiment at European Synchrotron Radiation Facility (ESRF, Grenoble) (Gurzadyan et al. in Mod Phys Lett A 20:1, 2005, Nuovo Cimento 122:515, 2007, Proceedings of the XII M. Grossmann meeting on general relativity, vol B. World Scientific, p 1495. arXiv:1004.2867, 2012; Bocquet et al. in Phys Rev Lett 104:241601, 2010). Using the GRAAL data we now get a new constraint on one of the key tests of Special Relativity—the Kennedy–Thorndike experiment (Kennedy and Thorndike in Phys Rev 42:400, 1932) in probing light speed invariance with respect to the velocity of the observer (apparatus). Our analysis takes advantage of GRAAL’s setup where two separate energy scales are involved: first, via the position of the Compton edge determining the light speed in the reference frame of incident 6 GeV electrons within the tagging system, second, in the calorimeter via the 1.27 MeV photons of the 22\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{22}$$\end{document}Na source. The two energy scales are engaged to each other through production of η\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\eta $$\end{document} mesons by tagged laser Compton backscattered γ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma $$\end{document}-rays. The accuracy of the calibration and stability of energies reached in each section enable us to obtain the limit of 7×10-12\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$7 \times 10^{-12}$$\end{document} for the Kennedy–Thorndike test, which improves the currently existing limits by three orders of magnitude.

The isotropy of the speed of light - the fundamental postulate of Special Relativity (SR) constrains conceptions of time, space and the existence of a preferred cosmological reference frame. Consequently, this phenomenon has been subject to considerable experimental scrutiny. Most isotropy tests are two-way Michelson-Morley type tests which established the isotropy of the two-way speed in 1881. These approaches provide no experimental limit for the one-way (single-trip) isotropy of the speed of light which is still unresolved. Here we consider Fizeau-type experiments to test the isotropy of the one-way speed of light. Our theoretical and experimental design suggests that our approach is 2600 times more sensitive than that of previous Fizeau-type experiments and 2000 times more sensitive than Michelson-Morley type two-way tests. We present our experimental methodology as well as initial calibration results for our experimental apparatus.

The conceptualization of time and the constancy of the speed of light In this work we show that the null result of the Michelson-Morley experiment in vacuum is deeply connected with the notion of time. It can be deduced without any mathematics only from the assumption that all good clocks can be used to measure time with the same results, independently of the machinery involved in their manufacturing. A second important assumption, intrinsic to the very notion of time, is that clocks measure time in the same way in different frames, i.e., the notion of time is the same in all inertial frames. Under this assumption, we point out that the "postulate" of constancy of the "two-way" speed of light in vacuum in all frames independently of the state of motion of the emitting body is also strongly related to the concept of time, together with the existence of a limit speed in the "rest frame". This postulate simply results from the construction of clocks where tic-tacs are made by objects traveling with the limit speed. Published as: Eur. J. Phys. 26 (2005) S117-S123 DOI: 10.1088/0143-0807/26/6/S05 arXiv categories: physics.ed-ph physics.gen-ph

Physicists conducted experiments to attempt to make this question become clear. The Michelson-Morley Experiment showed that there was no medium through which light travelled. It showed that there is no Luminiferous aether. The easiest way to see the general idea is to imagine a very fast spaceship moving at one half the speed of light from one star to another. The spaceship has two light-speed meters, one pointing backward and one pointing forward. Since the spaceship is moving away from the photons given off by the yellow star, and running toward the photons given off by the blue star, our ordinary experience leads us to expect that we would measure the speed of the yellow photons as 150 000 kilometres per second, and the speed of the blue photons as 450 000 kilometres per second. However both photons are measured at 300 000 km/s. Thereby this result indicates that speeds do not change relative to the movement of the spaceship. Recent research A recent study is much more precise than the one by Michelson and Morley, but it still shows that the speed of light is constant no matter which direction one is moving in.[1] References - ↑ "Michelson–Morley experiment is the best yet".

The Michelson and Morley 1887 Experiment and the Discovery of Absolute Motion Physics textbooks assert that in the famous interferometer 1887 experiment to detect absolute motion Michelson and Morley saw no rotation-induced fringe shifts - the signature of absolute motion; it was a null experiment. However this is incorrect. Their published data revealed to them the expected fringe shifts, but that data gave a speed of some 8km/s using a Newtonian theory for the calibration of the interferometer, and so was rejected by them solely because it was less than the 30km/s orbital speed of the earth. A 2002 post relativistic-effects analysis for the operation of the device however gives a different calibration leading to a speed >300km/s. So this experiment detected both absolute motion and the breakdown of Newtonian physics. So far another six experiments have confirmed this first detection of absolute motion in 1887. Published as: Progr.Phys. 3 (2005) 25-29 arXiv categories: physics.gen-ph

the proposed fixed aether, culminating in the 1887 Michelson–Morley experiment which only confirmed the constant speed of light. Several fixes to the In physics, the special theory of relativity, or simply special relativity, is a scientific theory of the relationship between space and time. In Albert Einstein's 1905 paper, "On the Electrodynamics of Moving Bodies", the theory is presented as being based on just two postulates: The laws of physics are invariant (identical) in all inertial frames of reference (that is, frames of reference with The principle of relativity – the laws by which the states of physical systems undergo change are not affected, whether these changes of state be referred to the one or the other of two systems in uniform translatory motion relative to each other. The principle of invariant light speed – "... light is always propagated in empty space with a definite velocity [speed] c which is independent of the state of motion of the emitting body" (from the preface). That is, light in vacuum propagates with the speed c (a fixed constant, independent of direction) in at least one system of inertial coordinates (the "stationary system"), regardless of the state of motion of the light source. The constancy of the speed of light was motivated by Maxwell's theory of electromagnetism and the lack of evidence for the luminiferous ether. There is conflicting evidence on the extent to which Einstein was influenced by the null result of the Michelson–Morley experiment. In any case, the null result of the Michelson–Morley experiment helped the notion of the constancy of the speed of light gain widespread and rapid acceptance. The derivation of special relativity depends not only on these two explicit postulates, but also on several tacit assumptions, including the isotropy and homogeneity of space and the independence of measuring rods and clocks from their past history. Special relativity in its Minkowski spacetime is accurate only when the absolute value of the gravitational potential is much less than c2 in the region of interest. In a strong gravitational field, one must use general relativity. General relativity becomes special relativity at the limit of a weak field. At very small scales, such as at the Planck length and below, quantum effects must be taken into consideration resulting in quantum gravity. But at macroscopic scales and in the absence of strong gravitational fields, special relativity is experimentally tested to extremely high degree of accuracy (10−20) and thus accepted by the physics community. Experimental results that appear to contradict it are not reproducible and are thus widely believed to be due to experimental errors. Special relativity is mathematically… The…

A New Light-Speed Anisotropy Experiment: Absolute Motion and Gravitational Waves Detected Data from a new experiment measuring the anisotropy of the one-way speed of EM waves in a coaxial cable, gives the speed of light as 300,000+/-400+/-20km/s in a measured direction RA=5.5+/-2hrs, Dec=70+/-10deg S, is shown to be in excellent agreement with the results from seven previous anisotropy experiments, particularly those of Miller (1925/26), and even those of Michelson and Morley (1887). The Miller gas-mode interferometer results, and those from the RF coaxial cable experiments of Torr and Kolen (1983), De Witte (1991) and the new experiment all reveal the presence of gravitational waves, as indicated by the last +/- variations above, but of a kind different from those supposedly predicted by General Relativity. The understanding of the operation of the Michelson interferometer in gas-mode was only achieved in 2002 and involved a calibration for the interferometer that necessarily involved Special Relativity effects and the refractive index of the gas in the light paths.

of a ship through a still atmosphere will make " a wind." In 1887 Michelson and Morley tried to detect this. Theoretically, a ray of light in the direction