The Impossible Measurement of the Speed of Light and the Ether

The speed of light is a fundamental constant of modern physics, whose invariance constitutes the basic postulate of Special Relativity (SR). However, an epistemological and operational analysis demonstrates that no laboratory experiment has ever directly measured the one-way speed of light. All empirical determinations—from classical Michelson-Morley interferometric experiments to modern detections by the LIGO and Virgo collaborations—measure only the average velocity over closed round-trip paths (two-way speed of light), or compare the speed of electromagnetic waves with the speed of gravitational waves, without making direct measurements. This paper analyzes the circular and tautological nature of distant clock synchronization and compares the conventional relativistic approach with dynamically compensated models (Lorentz and Selleri aether theory and hydrodynamic theories), highlighting the intrinsic impossibility of measuring the one-way speed without assuming an a priori postulate. Experimental results therefore cannot exclude the presence of the aether, and dynamically and hydrodynamically compensated models, such as the Lorentz aether theories, the Selleri transformations and the Subtle Particle Model SPM [2], the Repulsive Gravity Model RGM [3] [4] and the MODEC [1], are mathematically and experimentally equivalent in closed paths.