Analysis of the Essence and Applicable Boundaries of Relativity from the Perspective of Light String First-Principle Unified Theory

Based on the complete axiom system of the Light String First-Prprinciple Unified Theory, this paper reinterprets the core concepts of relativity from an essential physical perspective while fully acknowledging the mathematical accuracy and experimental validity of both special and general relativity. It reveals the physical essence of relativistic mass, upper limit of light speed, spacetime curvature, and gravitational constant. It clarifies the position of relativity as an accurate mathematical tool at the phenomenal level and distinguishes between phenomenal description and essential interpretation. This paper also cites the first-principle derivation of the gravitational constant G from the Light String Theory, verifying the self-consistency and explanatory power of the theoretical framework, and provides a new approach toward a unified fundamental physics framework.