This paper, as the third in the "Mathematical Essence of the Universe" series, extends the Qi theory framework established in Parts 1 and 2 to the domains of gravity and cosmology. In Part 1, we demonstrated the inevitability of the golden ratio Φ based on the "Principle of Optimal Filling" and "Optimal Robustness", derived the necessity of absolute spacetime from the Φ law, and defined the fundamental entity—Qi. In Part 2, we constructed a seven-level material structure spectrum from Qi to black holes, clarifying that photons are core planar crystal clusters + crystal cluster clouds (two-dimensional recursive nested structures) and massive particles are three-dimensional recursive nested structures (electrons with 11 layers, protons with about 20 layers), and successfully derived the fine-structure constant and the electron mass. This paper first proposes a novel interpretation of gravitational phenomena: gravity is not the curvature of spacetime, but a modulation effect of matter on the distribution of Qi recursive crystal clusters in absolute spacetime. Absolute spacetime itself is flat and isotropic, but the Qi entangled pairs and higher-order recursive crystal clusters distributed within it are not uniform—the experimental evidence of 0.8 K photon emergence in Part 4 shows that photons appear probabilistically in the vacuum background, demonstrating the existence of recursive fluctuations in the crystal cluster distribution. The presence of matter alters the local density and ordering of crystal clusters, producing an effective potential field that influences the motion of other particles. We rigorously prove that this theory is completely equivalent to general relativity in the weak-field limit, accurately reproducing the four classic tests: Mercury's perihelion precession, light deflection, gravitational redshift, and radar time delay. Furthermore, from Qi recursive dynamics, we prove that the constancy of the speed of light is a natural consequence of the transverse wave speed in the Qi lattice; thus absolute spacetime is mathematically isomorphic to Minkowski spacetime of special relativity. In strong-field regions (black hole horizons, neutron star mergers, etc.), Appendix A's multi-layer shell model demonstrates consistency between Qi theory and general relativity at the macroscopic thermodynamic level, while offering distinguishable predictions in quasinormal mode spectra and gravitational wave polarization modes; hence strong-field equivalence is also established. Second, we propose a six-stage cosmic evolution conjecture governed by the Φ law and Optimal Robustness, providing a unified descriptive framework for the history of the universe from creation to end. Each stage transition is triggered by critical conditions determined by the Φ law and recursive coupling. This evolutionary sequence is mathematically isomorphic to the seven-level material structure spectrum of Part 2, together forming a complete picture from static structure to dynamic evolution. Finally, we outline future research directions. Qi theory, as a logically self-consistent, mathematically precise, and empirically adequate new paradigm, opens a promising path toward understanding the ultimate nature of the universe. A Chinese version of this paper is also included in the uploaded files.
Lin Hao (Sat,) studied this question.