The Yin–Yang Cosmological Model.

The Yin–Yang Cosmological Model (YY) proposes that our observable universe is the three-dimensional interface between two complementary four dimensional hyperspheres: Yin, anchored at the Planck scale, and Yang, expanding at cosmological scales. Time emerges from Yin’s fundamental rotations, while cosmic expansion is governed by Yang’s radius. This simple geometric construction eliminates the need for singularities, inflation, dark matter particles, or a cosmological constant. Instead, matter, radiation, and interactions arise as manifestations of interface dynamics. From a small set of geometric parameters — the interface thickness 𝛿 = 127/ 6 ℓ𝑃 , Yang’s present radius 𝑅𝑌𝑎𝑛𝑔 ≃ 1.31 × 1026 m, and the Planck length itself — the model reproduces key observables: the universe’s age (∼ 13.8 Gyr), the Hubble constant ( 𝐻0 ≈ 70 km s−1 Mpc−1 ), and the deceleration parameter ( 𝑞0 ≈− 0.3 ) without invoking dark energy. The cosmic microwave background is reinterpreted as the fossil imprint of Yin’s earliest rotations, while photon propagation experiences a cumulative attenuation of order 10% over a Hubble time due to geometric slip. Fundamental constants also acquire geometric meaning: Newton’s gravitational constant G emerges from the coupling of Yin’s Planck-scale dynamics with Yang’s curvature, and the fine-structure constant 𝛼 ≈ 1/137 appears as a harmonic ratio from photon confinement within the interface. The model thus unifies gravity and electromagnetism as fundamental roots, with the strong and weak forces arising as emergent effects of confinement and phase instability. The Yin–Yang framework offers testable predictions, including photon attenuation detectable by comparing electromagnetic and gravitational-wave distances, and subtle deviations from ΛCDM distance–redshift relations at 𝑧 ≳ 1. These features provide a concrete observational path to confront the YY model with present and future data, positioning it as a coherent geometric alternative to standard cosmology.