We propose a cosmological and foundational physics hypothesis in which the speed of light in vacuum, \(c\), is not only a relativistic invariant but also the manifestation of a primordial propagation mechanism originating in the extreme conditions of the Big Bang. In this framework, the photon is viewed as a local excitation subject to absorption-emission interactions, while an underlying wave-like carrier ensures constant propagation speed. This distinction is intended to provide a unified interpretation of the constancy of \(c\), the quantized nature of light-matter exchange, and the propagation of gravitational signals.At the cosmological scale, we develop an alternative model of the Universe based on a shell-like geometry and on a dynamic ether-space substrate, in which cosmic expansion, large-scale structure formation, and certain properties of the cosmic microwave background may be interpreted as manifestations of the continuous unfolding of this primordial wave. The model also offers a possible framework for understanding the rapid formation of early galaxies, ultra-long gamma-ray bursts, and recent JWST observations as signatures of a deeper cosmological organization than that described by the standard model. Finally, we discuss several observational tests, including spectroscopy of distant quasars, gravitational waves, CMB anisotropies, and compact structures observed in the early Universe. The aim of this work is to formulate a coherent, speculative yet falsifiable framework that may open discussion on the physical origin of the constant \(c\), the nature of the vacuum, and the emergence of spacetime.