In general relativity, the interaction between gravity and light fundamentally has been based in quantum light theory on the gravitational-electromagnetic interaction. Instead of a curved space-time continuum in general relativity, the curved path of a beam of light within a gravitational field in quantum light theory has been based on the interaction between the gravitational field and an accelerated electromagnetic field e.g., the curved path of a beam of light, deflected by a black hole, in which the beam of light is generating its own gravitational field by its own acceleration. The deflection of a beam of light by the gravitational field of a black hole is a pure example of gravitational-gravitational interaction between two independent gravitational fields. In Quantum Light Theory (QLT) the electromagnetic energy gradient creates through a second order Lorentz transformation the gravitational field, which determines the interaction force density between the confinements of Light GEONs, gravitational electromagnetic confinements, published by John Archibald Wheeler in 1955 and a second gravitational field. In this way the property for GEONs of mass has been generated by its own gravitational field. A valuable way to test theories describing the interaction between gravity and light is the phenomenon of gravitational redshift. The differences in result between measuring the gravitational redshift between an atomic clock in an ESA satellite in a Galileo orbit and a corresponding atomic clock at a ground station are smaller than 17 digits after the decimal point, between general relativity and quantum light theory.