Reinterpreting Cosmological Redshift and CMB Temperature

The standard view that the Cosmic Microwave Background cooled from 3000 K to 2.7 K because space itself expanded assumes that vacuum can act as a thermodynamic cooler. No laboratory experiment shows that free photons lose energy by a factor of 1100 due to expansion alone while preserving a perfect blackbody spectrum and Wien's law. Gravitational redshift, by contrast, is experimentally verified in the Pound-Rebka experiment as an energy exchange. Within the Dynamic Quantum Vacuum model, this is reinterpreted as energy exchange between the photon and the vacuum. Photons gain energy moving toward a mass and lose energy moving away, conserving total energy. In this view, Planck's constant appears as a coefficient of vacuum energy change within photon volume. This provides a physical mechanism for frequency shifts in time-invariant space and suggests cosmological redshift may be accumulated gravitational redshift rather than expansion of space.