Physical Interpretation of the Origin of the Fixed‑Value Speed of Light

In the framework of modern physics, the speed of light (approximately 300 000 km/s) serves as a fundamental physical constant widely adopted in core theories including relativity and quantum mechanics. For a long time, academic research has focused on its measurement and application, while the underlying physical origin for this specific numerical value remains unelaborated; it is merely treated as a given boundary condition of the universe. Based on the self‑balancing dynamic property of space, this paper breaks away from the conventional research perspective of photon motion and vacuum medium. Combined with existing observational phenomena and verified experimental data, we propose an inference: the speed of light is not an intrinsic motion property of microscopic particles, but an underlying propagation‑constraint threshold inherent to the self‑balancing dynamics of cosmic space. This fixed value of the speed of light is non‑random. It is an essential physical condition set by space to sustain the generation and structural stability of microscopic particles and guarantee the persistence of macroscopic matter. Without introducing the hypotheses of vacuum condensation and vacuum phase transition, this paper takes the characteristic scale of 10-15m for microscopic‑dynamic spatial domains as the core basis to interpret the internal mechanism behind the fixed‑value speed of light. A physical causal chain “space constraint — fixed‑value speed of light — matter stability” is constructed, offering new insights for theoretical research on the origin of fundamental physical constants.