We report Relativity tests based on data from two simultaneous Michelson-Morley experiments, spanning a period of more than one year. Both were actively rotated on turntables. One (in Berlin, Germany) uses optical Fabry-Perot resonators made of fused silica; the other (in Perth, Australia) uses microwave whispering-gallery sapphire resonators. Within the standard model extension, we obtain simultaneous limits on Lorentz violation for electrons (5 coefficients) and photons (8) at levels down to 10 −16 , improved by factors between 3 and 50 compared to previous work.

We present an improved laboratory test of Lorentz invariance in electrodynamics by testing the isotropy of the speed of light. Our measurement compares the resonance frequencies of two orthogonal optical resonators that are implemented in a single block of fused silica and are rotated continuously on a precision air bearing turntable. An analysis of data recorded over the course of one year sets a limit on an anisotropy of the speed of light of Ác=c $ 1 Â 10 À17 . This constitutes the most accurate laboratory test of the isotropy of c to date and allows to constrain parameters of a Lorentz violating extension of the standard model of particle physics down to a level of 10 À17 .

Lorentz symmetry is a foundational property of modern physics, underlying the standard model of particles and general relativity. It is anticipated that these two theories are low-energy approximations of a single theory that is unified and consistent at the Planck scale. Many unifying proposals allow Lorentz symmetry to be broken, with observable effects appearing at Planck-suppressed levels; thus, precision tests of Lorentz invariance are needed to assess and guide theoretical efforts. Here we use ultrastable oscillator frequency sources to perform a modern Michelson–Morley experiment and make the most precise direct terrestrial test to date of Lorentz symmetry for the photon, constraining Lorentz violating orientation-dependent relative frequency changes Δν/ν to 9.2±10.7 × 10−19 (95% confidence interval). This order of magnitude improvement over previous Michelson–Morley experiments allows us to set comprehensive simultaneous bounds on nine boost and rotation anisotropies of the speed of light, finding no significant violations of Lorentz symmetry.

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 findκ ZZ e− = (−1.9 ± 5.2) × 10 −15 . Within the Robertson-Mansouri-Sexl test theory, our measurement restricts the isotropy violation parameter β − δ − 1 2 to (−2.1 ± 1.9) × 10 −10 , corresponding to an eightfold improvement with respect to previous non-rotating measurements. Local Lorentz invariance (LLI) is an essential ingredient of both the standard model of particle physics and the theory of general relativity. It states that locally physical laws are identical in all inertial reference frames i.e. independent of velocity and orientation. However, several attempts to formulate a unifying theory of quantum gravity discuss tiny violations of LLI. Modern high precision test experiments for LLI are considered as important contributions to these attempts, as they might either rule out or possibly reveal the presence of such effects at some level of measurement precision. An experiment of particular sensitivity to LLI-violation is the Michelson-Morley (MM) experiment [1] testing the isotropy of the speed of light. Modern versions employ high finesse electromagnetic resonators, whose eigenfrequencies depend on the speed of light c in a geometry dependent way (ν ∼ c/L for a linear optical Fabry-Perot cavity of length L). Thus a measurement of the eigenfrequency of a resonator as its orientation is varied, should reveal an anisotropy of c/L. Recently, such an anisotropy of c has been described as a consequence of broken Lorentz symmetry within a test model called Standard Model Extension (SME) [2]. This model adds all LLI violating terms that can be formed from the known fields and Lorentz tensors to the Lagrangian of each sector of the standard model of particle physics. It thus allows a consistent and comparative analysis of various experimental tests, including the MM experiment. The latter however, is also often interpreted according to a kinematical test theory, formulated by Robertson [3] and Mansouri and Sexl [4] (RMS). This test theory assumes a preferred frame, commonly adopted to be the cosmic microwave background (CMB). Combinations of three test parameters (α, β, δ) then model an anisotropy as well as a boost dependence of c within a frame moving at velocity v relative to the CMB. In view of the substantial impact that LLI-violation would have all over physics, the new approach of the SME has triggered a new generation of improved MMtype experiments [5,6,7,8]. So far all of these recent measurements relied solely on Earth's rotation for varying resonator orientation, which was made possible by the low drift properties of cryogenical...