Mechanical Resolution of the Hubble Tension: Viscous Drag Gradients in the 1D Vacuum Medium

This paper provides a purely mechanical solution to the Hubble Tension—the 9% discrepancy in the measured expansion rate of the universe (H0). Within the Universal Sheet Tension (UST) Model framework, cosmic expansion is redefined as the kinetic recoil of 3D matter inclusions through an elastic 1D substrate. We demonstrate that the discrepancy between local and CMB-based measurements is a direct result of density-dependent viscous drag (η) within the 1D medium. This "Viscous Drag Gradient" eliminates the need for Dark Energy or cosmological fine-tuning by accounting for the evolving viscosity of the vacuum substrate.