Elastic Spacetime Theory: Deriving All Fundamental Constants from (6+2)D Geometry

We present Elastic Spacetime Theory (EST), in which spacetime is modeled as a continuous elastic medium with 6 spatial and 2 temporal dimensions — denoted (6+2)D. The theory has zero free parameters: every fundamental constant is derived from the geometry of the medium using only three empirical anchors (the speed of light c, the electron mass m_e, and the age of the universe t_u). From these three inputs and the dimensional structure (D_s=6, D_t=2), we derive 22 physical quantities, including: the fine-structure constant α=1/137.036 to <0.01% error; the Planck-to-electron mass ratio to 0.002%; the Higgs boson mass to 0.12%; all three charged lepton mass ratios to sub-percent accuracy; the Planck length, gravitational constant G, and reduced Planck constant ℏ as fully derived quantities; the density and elastic modulus of the spacetime medium; and the quantum coherence length (~98 light-years). Beyond numerical derivations, the framework provides geometric explanations for: mass as a temporal offset, electric charge as a projection of that offset, vacuum transparency as 1−α, special-relativistic time dilation as geometric projection onto the temporal plane, and CPT symmetry as a geometric tautology. Competing dimensional configurations, including (3+2)D, are excluded by existing experimental data without new experiments. The theory makes eight falsifiable predictions, including a new particle at ~245–250 GeV. Three independent researchers — Lanciani (1999), the present author (2025), and Kulkarni (2026) — converged on related geometric structures without prior contact. Companion volumes: DOI 10.5281/zenodo.18911034