The Illusion of Dark Energy: Cosmic Acceleration Explained by Gravitational Horizon Lag and Hierarchical Coupling

The standard ΛCDM model introduces dark energy as an ad hoc component to explain cosmic acceleration. This work proposes an alternative based on the experimentally confirmed fact that gravity propagates at light speed. We distinguish the optical event horizon and gravitational coupling horizon, demonstrating that the FRW framework neglects gravitational lag and indirect long-range gravitational coupling across the horizon. Using discrete shell models (3, 10, 100 layers) and a continuous infinite radial integral, the deceleration parameter converges from q₀≈-0.48 to q₀→-0.55, matching observations with negligible error. No exotic physics is required. We conclude dark energy is a computational artifact, not a physical substance.