Unified Cosmic Mechanics Evolution Theory (VI) The Relationship Between Relativity, Classical Mechanics, and Quantum Mechanics

There are significant differences in the mathematical forms of classical mechanics, special relativity, general relativity, and quantum mechanics, which limit the study of the unity of their physical essence. Based on the Unified Cosmic Mechanics Evolution Theory, this paper proposes that the "momentum unit" is the only fundamental reality of the universe, and all physical phenomena emerge from the superposition, distribution, interaction, and statistics of momentum units. The study clarifies the physical reality of the core state evolution of the cosmic system, reconstructs the essence of force and divides it into "additive force" and "multiplicative force". It elucidates that special relativity originates from the compression of the perceptual space-time window when particles move, while general relativity originates from the conservation of internal evolution capacity of particles in motion. Both emerge the Pythagorean conservation relationship and the same Lorentz factor, while clarifying the dynamic connotation of the mass-energy equation. Finally, the three major mechanical systems are unified under three core principles, verifying that relativity and quantum mechanics are natural extensions of the same set of dynamic rules under different constrained conditions.