Essential Reconstruction of the Eötvös Experiment: From Equivalence Principle Test to Verification of Metric Benchmark Uniformity

The Eötvös experiment and its high-precision repetitions are regarded by traditional physics as the core experimental evidence for the equality of gravitational mass and inertial mass, and form the observational foundation of the weak equivalence principle in general relativity. Starting from the metric axioms of Time Field Theory (TFT), this paper systematically reconstructs the physical connotation of the experiment: the Eötvös experiment does not verify the equivalence of two independent masses, but the universality of the inertial metric benchmark under the same time field — the inertial mass of all matter shares a uniform proportional constant with its own rest mass. In Newtonian mechanics, this equality is an unexplained empirical coincidence; in general relativity, it is elevated to a fundamental postulate of geometric gravitation; within the TFT framework, it is a logical necessity of the axiom of metric self-consistency. This paper further points out that ground-based mechanical experiments are inherently trapped in a conceptual circularity of "measuring inertia with inertia", and cannot achieve a decisive distinction between TFT and general relativity. The combination of natural extreme scenarios of cosmic objects and unbiased photon measurement constitutes the fundamental approach to break out of the mass conceptual circularity and examine the nature of gravitational sources.