Riemann's Unfinished Enterprise: The Physical Root of Metric Benchmark Variability

In 1854, Bernhard Riemann proposed a proposition more profound than "space curvature" in his lecture On the Hypotheses Which Lie at the Bases of Geometry: the metric benchmark may vary with position, and the geometric appearance of space is entirely determined by this variability. He explicitly left the fundamental question of "what physical process determines the metric benchmark" to future empirical science. In 1915, Albert Einstein provided the first systematic answer: the metric benchmark (metric tensor) is determined by matter distribution. However, in the standard interpretation, he reified the metric itself, transforming "variable metric benchmark" into the geometric ontology of "spacetime itself is curved". In 2026, Metretics Dynamics (formerly Time Field Theory, TFT) offers a second answer: the metric benchmark is represented by the time field γ, whose distribution is strictly constrained by the flux conservation principle; space itself remains flat, and the geometric image of "spacetime curvature" in general relativity is essentially the metric projection of the inhomogeneity of the γ field. This paper traces the complete intellectual lineage from Riemann to Einstein and then to TFT, arguing that TFT is not a revision of general relativity, but a return to Riemann's more original metrological starting point, completing Riemann's unfinished enterprise with a more parsimonious physical entity. The core task of this paper is not to derive new mathematical formulas, but to sort out the intellectual context and clarify the inheritance and transcendence of TFT relative to Riemann and Einstein on the "metric benchmark problem".