The supposed expansion of the universe is a gravitational mirage caused by the relativistic energy loss of photons exchanged from large distances, considering the distant emitter O as the center of a homogeneous universe of density D with radius up to the observer (us) R. The gravity exerted on the photon by the universe outside the sphere of radius R is null, and is added to the gravity exerted on the photon by the universe inside the sphere of radius R, from the emitter O. This subjective gravity (perceived from where we are) generates the gravitational pull on the photon towards its emitter, generating the redshift that we observe. I explain it here and in X.
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