Redshift of photons penetrating a hot plasma

A new interaction is derived, which is important only when photons penetrate a hot, sparse electron plasma. When photons penetrate a cold and dense electron plasma, they lose energy through ionization and excitation, through Compton scattering on the individual electrons, and through Raman scattering on the plasma frequency. But when the plasma is very hot and has low density, such as in the solar corona, the photons lose energy also in a newly derived collective interaction with the electron plasma. The energy loss of a photon per electron is about equal to the product of the photon’s energy and one half of the Compton cross-section per electron. The energy loss (plasma redshift of the photons) consists of very small quanta, which are absorbed by the plasma and cause a significant heating. In quiescent solar corona, this heating starts in the transition zone to the solar corona and is a major fraction of the coronal heating. Plasma redshift contributes also to the heating of the interstellar plasma, the galactic corona, and the intergalactic plasma. Plasma redshift explains the solar redshifts, the redshifts of the galactic corona, the cosmological redshifts, and the cosmic microwave background. The plasma redshift, when compared with experiments, shows that the photons’ classical gravitational redshifts are reversed as the photons move from the Sun to the Earth. As seen from the Earth, a repulsion force acts on the photons. All these findings lead to fundamental changes in the theory of general relativity and in our cosmological perspective.