The Gravitational Olbers' Paradox and the Entropic Accelerating Universe

Submitted to European Physical Journal Plus, 20 May 2026 (manuscript EPJP-D-26-03547). Editor assigned 21 May 2026. Uploaded to Zenodo to establish public timestamp of the submitted version, pending peer review. This is the exact submitted manuscript.The accelerating expansion of the Universe is reframed as the resolution to a gravitational analogue of Olbers' Paradox. Because gravitational influence propagates at the speed of light—confirmed by the binary neutron star merger GW170817—each observer is surrounded by a cosmological event horizon beyond which matter exerts no gravitational pull. The horizon is a thermodynamic object: it possesses a temperature proportional to the Hubble parameter and an entropy proportional to its area. As the universe expands, the horizon grows and its entropy S_H ∝ R²_H increases geometrically — present in any expanding spacetime regardless of matter content. The second law of thermodynamics drives the universe toward states of larger horizon radius. The resulting entropic pressure, P = −(2/3)ρ_crit c², yields an effective equation of state ω_eff = −2/3, providing accelerating expansion with no vacuum energy contribution and dissolving the cosmological constant problem without fine-tuning. The predicted dynamical dark energy, with ω ≠ −1 evolving with redshift, is consistent with the 4.2σ deviation from ΛCDM reported by the DESI Year 3 (DR2) survey.