Direct Detection of Two-Way Light Speed Deviation with a First-Order Sensitive Interferometer*

Conclusively testing two-way light speed invariance faces two challenges: traditional Michelson–Morley interferometric tests are limited to second-order sensitivity, v²/ c², constraining deviation detection to ~1 km/s, and their reliance on hypothetical preferred frames yields only upper limits, not conclusive results. Modern cavity-based tests measure frequency shifts rather than direct time-of-flight of light, leaving questions about validity.

A novel interferometric setup is designed to detect two-way light speed deviations with first-order sensitivity, (c±v), where v is a tunable deviation parameter independent of the choice of reference frame. Our configuration adopting innovative closed-path design can directly detect two-way light speed deviations with v as small as 0.1 m/s — a 10^4-fold improvement over traditional M–M interferometer. Importantly, this approach enables conclusive test by avoiding dependency on a hypothetical frame. This configuration aligns with the Sagnac effect and enables testing a new prediction of Sagnac effect in non-rotating inertial systems per Asymmetry Theory.

The implementation of this theoretical proposal will close a century-old gap in two-way light speed testing.