Reevaluation of the Observable Universe Scale Based on the Hypothesis of No Dark Components

This work presents a conceptual reevaluation of the observable universe scale under the hypothesis that dark matter and dark energy do not exist. Instead of interpreting cosmological redshift as evidence of metric expansion of space, the paper explores an alternative interpretation in which redshift arises from photon energy reduction associated with cosmic thermal cooling. By linking the photon energy–wavelength relation (E = hc/) with the thermodynamic temperature evolution of the universe, a framework is proposed in which wavelength stretching emerges from energy attenuation rather than geometric expansion. Within this perspective, the inferred cosmic scale may be significantly more compact than in standard cosmology, and the uniformity of the cosmic microwave background can be interpreted as a consequence of efficient thermal equilibration in a smaller early universe. The need for dark components is therefore reconsidered as potentially model-dependent. The paper is positioned as a physics-based thought experiment intended to stimulate discussion and critical examination of cosmological interpretation using established physical laws and radiation–matter interactions.