Two Laboratory Tests of Light Propagation in Vacuum: Transport-Synchronised One-Way Timing and Reflection from a Moving Mirror

This research proposes two complementary laboratory experiments to investigate fundamental assumptions concerning the propagation of light in vacuum and the experimental foundations of special relativity. The first experiment investigates one-way light propagation using transport-synchronised clocks. It employs two clock pairs mounted on a slowly rotating platform, with each pair synchronised locally by contact before one clock is transported to a position opposite its reference clock. At defined measurement events, the apparatus records forward and reverse one-way light-travel times alongside a round-trip measurement. Two perpendicular measurement arms provide an opportunity to investigate directional variations and their possible dependence on sidereal time. The theoretical analysis derives the measurable timing asymmetry and shows that, to first order, it depends on the combination (1 − 2k)u, where u represents the laboratory velocity relative to a hypothetical frame in which light is isotropic, and k characterises the assumed velocity dependence of clock rates. The experiment therefore examines the relationship between transport synchronisation and light-based synchronisation without claiming to measure a one-way speed independently of clock assumptions. Special relativity predicts a null result within the proposed measurement framework. The second experiment investigates competing kinematic descriptions of light reflection from moving mirrors in vacuum. Three reflection laws are compared: the relativistic law, a Galilean new-source emission law and a Galilean elastic-impact law. A unified mathematical treatment derives their respective reflected frequencies, wavenumbers, wavelengths and propagation velocities. The analysis examines phase continuity, energy–momentum balance and compatibility with the vacuum Maxwell dispersion relation, ω = c|k|. The research also reassesses the historical moving-mirror experiments of Michelson (1913), Majorana (1918), and Beckmann and Mandics (1965), identifying limitations in the extent to which their experimental configurations distinguish the competing reflection laws. In particular, the analysis examines why the 1965 high-vacuum interferometric experiment cannot distinguish the relativistic reflection law from the elastic-impact alternative. To address this limitation, a co-moving two-mirror interferometer is proposed. Its theoretical predictions distinguish the three reflection laws through changes in carrier phase and pulse-arrival time when the direction of mirror motion is reversed. The paper also discusses experimental feasibility, vacuum requirements, systematic uncertainties and possible decision criteria. Both experiments are proposals rather than completed experimental investigations. Their purpose is to provide falsifiable laboratory procedures for examining two distinct questions: whether transport-synchronised clocks and light-synchronised clocks produce consistent directional timing results, and whether light reflected from slowly moving macroscopic mirrors in vacuum follows the relativistic reflection law. The study does not claim experimental evidence against special relativity or establish an alternative theory of light propagation. Instead, it develops two complementary experimental frameworks, derives their predicted observables, identifies relevant theoretical constraints and specifies the measurements required for independent experimental evaluation. The work is relevant to the foundations of special relativity, relativistic optics, clock synchronisation, electromagnetic theory, optical interferometry and precision measurements of light propagation.