The Cyclic Universe: Mechanism of the Great Bounce in a Dynamic Cosmic Medium

The standard cosmological model (Big Bang) faces a fundamental conceptual barrier: the initial singularity, where density becomes infinite and physical laws break down. Furthermore, it offers no clear mechanism for the ultimate fate of the universe other than heat death or a catastrophic rip. This paper proposes an alternative model based on a dynamic cosmic medium with physical pressure and compressibility. We demonstrate that the universe undergoes eternal cycles of expansion and contraction driven by the interplay between inertial momentum, gravitational attraction, and the thermodynamic properties of the medium. Crucially, we show that as the universe contracts, the rising physical pressure of the compressed medium inevitably halts the collapse before a singularity can form. While the global collapse leads to a “Great Bounce,” local collapses (black holes) may reach a state of maximum compression and stabilize as ultra-dense remnants without undergoing a subsequent bounce. These objects then constitute the hidden mass component in intergalactic space. The model reinterprets the observed cooling of the Cosmic Microwave Background (CMB)