Dark photons could explain magnetic fields threading the entire cosmos

Cosmic magnetic fields spanning galaxy clusters and voids have no clean explanation in standard physics, and previous inflation-based mechanisms run into mathematical breakdowns. Coupling ordinary photons to 'dark photons' — hypothetical hidden-sector partners — sidesteps these failures and can generate fields of at least 10⁻¹³ Gauss without the strong-coupling or backreaction problems that plague existing models. If confirmed, the same minimal extension of electromagnetism could also address other open puzzles in cosmology.