Hydrodynamic Unification of the Quantum Vacuum and Gravity: The Zero-Entropy Superfluid Model

In this paper, we propose a unified cosmological and quantum model based on the hypothesis of a spatial substrate acting as a zero-entropy superfluid. Abandoning the geometric curvature of General Relativity in favor of rigorous fluid mechanics, the model redefines gravity not as an intrinsic attractive force, but as a mechanical pressure gradient (push gravity) generated by the presence of entropic topological defects (matter) within the primordial medium. We demonstrate how the thermodynamic condition of "zero entropy" resolves the thermal friction paradox that historically invalidated Le Sage-type gravitational theories. The framework is then extended to reinterpret black holes not as isolated singularities, but as active hydrodynamic valves, responsible for the generation of Cosmic Voids and Fermi Bubbles via bipolar water-hammer effects, thereby removing the theoretical necessity for repulsive dark energy. On a microscopic scale, phenomena such as the Casimir Effect and the Lamb Shift are recontextualized as direct manifestations of hydrodynamic pressure and the elastic polarization of the vacuum. Finally, the interaction of structured electromagnetic fields with the superfluid is analyzed, offering a mechanical basis for local turbulences and the manipulation of spatial pressure gradients. The model provides a coherent deterministic paradigm to unify macroscopic astrophysics and quantum electrodynamics.