The Hubble Tension in the Light of GG-Theory: The Hubble Constant as One Reading of a Derived Expansion History H(t)

For a century, "how fast is the universe expanding?" was a question answered by measuring. By 2026 the measuring had split: read from the afterglow of the Big Bang, the rate comes out near 67 (in astronomers' units); read from the local ladder of stellar distances, 73.50 ± 0.81 — a seven-sigma gap that no single method explains. This paper reads the disagreement through GG-Theory, in which the expansion rate was never a number to be measured but a function of time to be derived: a six-dimensional geometry fixes the cosmic recipe as exact expressions in π, Einstein's equations turn that recipe into the entire history H(t), and today's value is one snapshot of the curve — expressible in a single analytic line in the three laboratory constants , G_N, ℏ and two integers of the theory's ledger, giving 66.6 ± 0.2 — on the afterglow side of the split, 1.6σ from the CMB combination. More than ten of the standard model's fitted numbers re-emerge, unfitted, at the percent level. The early measurement needs no new physics. The local 73.5 is then the puzzle — and not, this paper's audit finds, a settled consensus: the 2026 landscape's forty-five determinations span 67–73, the seven sigma certifying one superb network's internal agreement. The paper prices the local reading honestly: a derived +2–3% neighborhood lift, and a named, still-open calibration residual, confronted with the field's own published corrections. The referee is scheduled: gravitational-wave standard sirens read the rate with no ladder and no afterglow, and GG-Theory predicts they converge near 67 — about twenty-one events from now. Near 73, this paper is wrong, and says so in advance. Either way the century-old "constant" has finished its work: what remains to be tested is not a number but a law. Part of the GG-Theory program, a series of preprints developing a six-dimensional geometric framework and its consequences for particle physics, cosmology, and open-system dynamics. The complete series is available at https://preprints.arisaka-gg.org/