A new Morley-Michelson experiment produced a more accurate determination that the speed of light is the same in all directions.
Schiller and colleagues Christian Eisele and Alexander Nevsky gathered data as they rotated their experiment about 175,000 times over about 13 months, with each rotation taking 90 seconds. To investigate whether Lorentz symmetry had been violated, the team analysed their time series of beat frequency measurements in terms a simplified version of the Standard Model Extension (SME) – a mathematical framework that describes violations to Lorentz symmetry in terms of 19 measurable parameters.
Schiller's experiment is sensitive to eight of these parameters and the team was able to show that four are zero to about two parts in 10^17; one is zero to about one part in 10^16; and three are zero to about two parts in 10^13. According to Schiller, this represents a factor of more than 10 improvement over previous measurements of these parameters and a factor of about 100 million better than Michelson and Morley's original experiment.
Outstanding. That should put even more severe constraints on any theory that has any Lorentz violation.