The standard cosmological model (ΛCDM) attributes the accelerated expansion of the universe to an unknown entity called dark energy — a concept that, despite its observational success, remains physically mysterious. In this paper, we present a hypothesis: Photon-Induced Vacuum Expansion (PIVE). We propose that the energy lost by photons during their cosmic journey — due to cosmological and gravitational redshift — does not vanish, but instead transfers to the quantum vacuum, generating a negative pressure that drives expansion. We emphasize two crucial physical insights: this expansion is not universal; it occurs only on large scales (between galaxy clusters) where gravitational binding is negligible. In dense regions (galaxies, clusters), gravity overwhelms the negative pressure, preventing local expansion. Photons are the only particles that can travel through all regions of the universe — even the most distant and unknown — without being directly observable or traceable. They move in all directions, and we can only measure their accumulated effects on the geometry of spacetime. The model introduces a photon–vacuum coupling constant α, modifies the Friedmann equations, and yields a direct, testable correlation between local photon flux and local expansion rate. The effective equation of state parameter wₑff naturally becomes < -1 in the past, consistent with recent DESI hints. We present this hypothesis with humility, fully aware of its limitations, and invite the scientific community to critically examine, test, and refine it. Science progresses through dialogue, and we offer this as a small contribution to that ongoing conversation.
Hossein Golkhoub (Tue,) studied this question.