Four-Dimensional Deterministic Dynamics: Unification of the Fluid Dynamic Continuum and Phenomenological Derivations from the Galactic Scale to the Microcosm

Contemporary physics faces an epistemological divergence due to the proliferation of unobservable parameters (dark sector) and non-physical algebraic singularities at infinite density. This work presents a unified deterministic framework based on the Hydrodynamic Continuity Principle, in which spacetime is described as a continuous, elastic, and viscous four-dimensional scalar medium, abandoning the hypothesis of the inert metric vacuum. The dynamic evolution is governed by an extended energy-momentum tensor that explicitly incorporates the torsional rigidity and intrinsic kinematic viscosity of the medium. The theory is homogeneously validated across the entire dimensional spectrum of physical reality: On the galactic scale, the model derives the flat asymptotic rotation velocity for the Andromeda Galaxy (M31) without resorting to dark matter halos; On the trans-Plutonian scale, it quantifies the constant ballistic deceleration and the stabilization of peripheral bodies in the solar system; On the planetary orbital scale, it calculates the secular correction to the terrestrial perihelion induced by solar torsional drag; In the subatomic microcosm, it resolves the electron as a standing wave soliton with a finite Compton radius, demonstrating that spin is real fluid dynamic circulation governed by open dynamical systems with parity-time (PT) symmetry. Finally, the Galilean experimental protocol is defined using a rotor with anisotropic architecture (V-Asymmetric 2026) under cryogenic ultra-high vacuum conditions and superconducting levitation, aimed at the direct interferometric measurement of the background torsional constant kappa_G ≈ 1.75 x 10^-10 m/s^2.