A Covariant Viscoelastic Spacetime with Gravitational Memory

The flattening of galactic rotation curves and the cosmological age crisis are twomajor challenges in modern astrophysics. This paper proposes a new gravitationalframework (KSG Theory) that reinterprets the empty vacuum not as a backgroundfor dark matter particles, but as a macroscopic medium possessing ’viscoelasticity’.Through energy relaxation dynamics driven by cosmological expansion, a singleuniversal constant κ = 0.86, which extends the age of the universe to 15.5 Gyr,is derived a priori. Remarkably, applying this cosmological constant directly togalactic dynamics perfectly reproduces the Radial Acceleration Relation (RAR) for175 galaxies in the SPARC database with an RMS scatter of σ ≈ 0.201 dex. Thissupersedes existing MOND models that rely on phenomenological curve-fitting.Furthermore, bootstrap statistical analysis demonstrates the scale independenceand robustness of this theory. To encourage rigorous cross-verification, this papertransparently provides all verification codes and data to the academic communityvia an Open Science approach.