Unified Gravity Model: Density-Pressure Coupling under the Spacetime Stacking Hypothesis and Multi-scale Quantitative Verification

To resolve the macro-micro fragmentation between general relativity and quantum field theory, this paper constructs a unified gravity model based on the spacetime monistic ontology: the rest mass of matter is not an independent source but a steady-state condensation product formed by continuous local stacking and solidification of spacetime. The model takes equivalent spacetime density and spacetime pressure as core physical quantities, decomposing the total equivalent spacetime density into five linearly superimposed components: vacuum background density, gravitational equivalent density, relativistic motion equivalent density, quantum fluctuation density, and spacetime stacking rate additional density, without requiring a separate rest mass density term. Through rigorous relativistic dynamics derivation, dimensional analysis, and logical self-consistency optimization, the core mathematical refinements are accomplished: the force expression is corrected to a volume integral form ensuring the equivalence principle; the Lorentz factor exponent in the motion equivalent density is corrected to yield the correct low-speed kinetic energy coefficient; the positive correlation between spacetime pressure and total density is unified. This paper presents for the first time the precise calibration values of all phenomenological parameters: c0=299792458.0166 m·s−1, ρc=1.8×1030 kg·m−3, ρvac=9.9×10−27 kg·m−3, K=1.47×104 m2⋅kg−1⋅s−2, calibrated solely by two independent experimental data sets: GPS gravitational clock deviation and surface gravitational acceleration, with parameters fixed thereafter. Multi-scale quantitative verification shows: on macroscopic scales, the model’s predictions for white dwarf gravitational redshift, high-energy muon lifetime, and binary neutron star orbital precession deviate from general relativity and observations by less than 5×10−4; on microscopic scales, predictions for the Casimir force and U238 α decay half-life deviate from experimental values by less than 0.2%, and the Heisenberg uncertainty principle is naturally derived. The model provides a unified explanation for the vacuum speed of light, the four fundamental forces, relativistic spacetime effects, holographic black holes, and superluminal cosmic expansion, and proposes eight falsifiable quantitative experimental predictions.