Note on Redshift and the Principle of Conservation of Energy

Redshift has always been associated with the Doppler effect, but sound waves and electromagnetic waves are different; if the association is wrong, the recessional speeds observed in the universe could be wrong. When redshift is observed, the energy of the photon is dropping; that change of energy cannot be explained by the Doppler effect. After a short history of the link Redshift-Doppler, the Ives-Stilwell experiment will be reinterpreted as a proof of special relativity, not a proof of the Doppler effect. A new proposal is presented: because of the acceleration of the expansion of the universe, there must be a potential field to explain that acceleration. A change of potential along that field could explain the change of energy corresponding to the redshift.