The Acopais Thesis: An Empirical Foundation for Spacetime

For over a century, theoretical physics has treated space and time as an abstract, four-dimensional geometric fabric that bends and warps in the presence of mass and velocity, while treating the speed of light ($c$) as an absolute universal constant across all frames of reference. While this mathematical geometry yields accurate predictions, it divorces physics from observable physical mechanics—resulting in unresolved paradoxes such as black hole singularities, the "Problem of Time" in quantum gravity, and imaginary numbers in space-like intervals. The Acopais Thesis—where ACOPAIS stands for A Change Of Position And Its Speed—restores an empirical, physical foundation to relativity and thermodynamics through five core mechanical principles: (1) Space is a physical medium, and time is strictly the measurement of energy changing position within that medium; (2) While inertial coasting represents the continuous relocation of existing kinetic energy, any alteration or reversal of a spatial trajectory requires a new expenditure of energy, establishing the thermodynamic arrow of time; (3) Gravity and motion through the spatial medium isotropically compress the empty space between matter and energy while slowing the local propagation velocity of energy—including the local speed of light ($c$)—by the exact same ratio; (4) Because an observer's physical ruler and internal atomic clock shrink and slow by identical proportions inside a compressed medium, every observer locally measures the speed of light as an invariant constant $c_0$ in all directions (satisfying the Michelson-Morley experiment and the Equivalence Principle), whereas across different frames—as empirically verified by GPS satellites and atomic clocks—the physical speed of light and rate of energy movement vary directly with local spatial density, with boundary transitions conserved via redshift and blueshift; and (5) The standard Minkowski spacetime interval ($s^2 = c^2\Delta t^2 - \Delta x^2$) breaks down into imaginary numbers for "space-like" separations specifically because zero energy physically relocates between the two events, confirming that real spacetime intervals exist only along causal pathways of energy movement.