GR-Razor Stress Tests-Pillar 8: The Horizon Problem Dissolved: A Finite Initial State Renders CMB Uniformity Inevitable Without Inflation

Cosmological Pangea Pillar 8 delivers the first clean quantitative result of the Cosmological Pangaea program. The horizon problem asks why regions of the cosmic microwave background separated by more than two degrees on the sky, which were never in causal contact under standard Big Bang evolution, share the same temperature to one part in 100,000. The standard resolution invokes cosmic inflation: an undetected scalar field introduced specifically to patch this problem by stretching a causally connected region to cosmological scales. Inflation does not dissolve the horizon problem. It relocates it to an earlier epoch and adds new physics to do so. In a finite initial state cosmology, the horizon problem does not arise. We calculate that a Pangaea object containing the mass-energy of the observable Universe at Planck density has a physical radius of 2.404 × 10⁻¹⁵ m. Its Schwarzschild radius is 4.455 × 10²⁶ m. The object is 1.85 × 10⁴¹ times smaller than its own causal horizon. Every part of it is in thermal contact with every other part not by assumption, not by a dynamical mechanism, but by the geometry of a finite dense object in general relativity. CMB uniformity to one part in 100,000 is a direct geometric consequence of common origin in a single causally connected object. No inflation required. No new fields. No new physics. The calculation uses nothing beyond the Schwarzschild radius formula of standard GR. The inflaton field was introduced to solve the horizon problem. The horizon problem does not exist in Cosmological Pangaea. The inflaton loses its primary motivation. This result is robust: varying the total mass by an order of magnitude in either direction changes the causal connectivity ratio by less than one order of magnitude. The object is causally self-connected by forty-one orders of magnitude. That is not a close call. This Pillar also formally retracts the fossil large-scale structure prediction from Pillar 6. Stage Two quantitative work showed the Jeans scale at any reasonable early-Universe density maps to scales far below the cosmic web cell size after full expansion. The series reports failures and retractions with the same directness as positive results. The fragmentation power spectrum, CMB acoustic peak reproduction, and Hubble tension calculation remain as open guillotines in the program. This is Pillar 8 of the GR-Razor Stress Tests series. The methodology and series context are documented in the Foundation Document. Final standing: Cosmological Pangaea survives every falsification test across twelve published Pillars. It eliminates the classical Big Bang singularity, replacing infinite-density breakdown with a finite, geometrically describable initial object. It dissolves the horizon problem without inflation, the causal connectivity of the initial state making the problem retroactively unnecessary. It reproduces the CMB spectral index at zero sigma deviation with no parameter adjustment. It reduces the Hubble tension from 5.0σ to 1.39σ from first principles, with full resolution within published LQC quantization uncertainty. It derives the arrow of time as a geometric consequence of symmetry breaking, with exactly zero initial gravitational entropy by Birkhoff's theorem. It connects the Hubble tension and the MOND galactic dynamics anomaly as linked consequences of the same parameter through Verlinde's entropic gravity relation, predicting the observed MOND acceleration scale within 8% without fitting. It does all of this while adhering strictly to general relativity and Occam's razor, introducing no new fields, no new particles, no fine-tuned potentials, and no action modifications. The GR-Razor series conclusively demonstrates a parsimonious, internally consistent alternative framework that resolves multiple independent cosmological tensions from first principles and is ready for full Boltzmann validation. 1. 10.5281/zenodo.18736909 – Independent Cosmological Falsification Series. 2. 10.5281/zenodo.18737186 – Inhomogeneous Backreaction as a GR-Internal Resolution to the JWST Early Galaxy Excess. 3. 10.5281/zenodo.18737308 – Vector and Tensor Mode Contributions in Relativistic Perturbation Theory as a GR-Internal Resolution to the JWST Early Galaxy Excess. 4. 10.5281/zenodo.18744293 – Frame-Dragging and Lense-Thirring Effects in Collapsing Structures as the Final GR-Internal Candidate for the JWST Early Galaxy Excess. 5. 10.5281/zenodo.18744659 – ΛCDM Under the GR-Razor Framework — A Full-Spectrum Stress Test of the Standard Cosmological Model. 6. 10.5281/zenodo.18745418 – Cosmological Pangaea: A Finite Structured Initial State as an Alternative to the Singular Big Bang. 7. 10.5281/zenodo.18748402 – Positioning of Cosmological Pangaea within Non-Singular Cosmologies: A Meta-Analysis and Theoretical Placement. 8. 10.5281/zenodo.18749361 – The Horizon Problem Dissolved: A Finite Initial State Renders CMB Uniformity Inevitable Without Inflation. 9. 10.5281/zenodo.18750240 – Consolidated Status of Cosmological Pangaea: Current Position, Quantitative Outcomes, and Open Questions. 10. 10.5281/zenodo.18750432 – ΛCDM Declared Incomplete, the Horizon Problem Dissolved, and the Hubble Tension Reduced to 1.39σ by a First-Principles Quantum Bounce. 11. 10.5281/zenodo.18751911 – The Arrow of Time: Geometric Origin of the Thermodynamic Arrow of Time: Weyl Curvature Growth During Fragmentation of a Finite Initial-State Universe. 12. 10.5281/zenodo.18755740 – The Navigable Universe Theory: Entropy as the Substrate of Physical Structure, Time's Arrow, and the Cosmic Sailor. 13. 10.5281/zenodo.18778921 – The Goldilocks Band as Cosmological Structure: Entropy Gradient Boundaries, Observer Emergence, and the Navigable Topology of the Cosmic Web. 14. 10.5281/zenodo.18790403 – The Engine and the Map: Scale-Dependent Thermodynamic Emergence and the Crossover Surface of Entropic Gravity in the Navigable Universe. 15. 10.5281/zenodo.18791558 – Cusps Never Formed: The Entropic Engine as the Geometric Resolution of the Core-Cusp, Missing Satellites, and Too-Big-to-Fail Problems Without Dark Matter, Feedback, or New Physics. 16. 10.5281/zenodo.18793031 – Geometric Baryogenesis: The Irreversible Weyl Excitation from Zero Gravitational Entropy as the Origin of Matter-Antimatter Asymmetry. 17. 10.5281/zenodo.18794156 – Surface Death: The Dimensional Collapse of the Entropy Gradient Network. 18. 10.5281/zenodo.18796471 – Distinction as the Irreducible Primitive: Deriving 3+1 Spacetime, Three Fermion Generations, and the Structural–Dynamical Partition from a Single Axiom. 19. 10.5281/zenodo.18805129 – The Geometry of the First Cut: Inevitability, Structural Repetition, and the First General-Relativity-Compliant Multiverse. 20. https://zenodo.org/records/18827471 – The Story of How Cosmological Pangaea Unfolded. 21. https://zenodo.org/records/18828910 – Nick Bostrom's Simulation Theory Put Through the GR-Razor Stress Tests. 22. https://zenodo.org/records/18829682 – String Theory Landscape + Eternal Inflation Multiverse Put Through the GR-Razor Stress Tests. 23. https://zenodo.org/records/18829899 – Supersymmetry (SUSY) Put Through the GR-Razor Stress Tests. 24. https://zenodo.org/records/18830031 – Grand Unified Theories (GUTs) Put Through the GR-Razor Stress Tests. 25. https://zenodo.org/records/18836774 – Loop Quantum Gravity (LQG) and Spin Foam Approaches Put Through the GR-Razor Stress Tests. 26. https://zenodo.org/records/18837671 – Many-Worlds Interpretation (MWI) Extensions and Quantum Cosmology Put Through the GR-Razor Stress Tests. 27. https://zenodo.org/records/18839355 – Causal Dynamical Triangulations (CDT) Put Through the GR-Razor Stress Tests. 28. https://zenodo.org/records/18840383 – The Architecture of Necessity: A Manifesto of the GR-Razor and Cosmological Pangaea's Complete Reset for the Field of Cosmology 29. https://zenodo.org/records/18867405 -The Resurrection Ship: A Framework for Civilizational Preservation in the Age of Artificial Intelligence (Philosophical) 30. https://zenodo.org/records/18869920 - The Geometry That Would Not Yield: Einstein-Rosen Bridges as Geometric Necessity Under the Distinction Axiom 31. https://zenodo.org/records/18878368 - Gravity and Electromagnetism as Dual Expressions of Distinction Preservation – A Native Cosmological Pangaea Unification 32. https://zenodo.org/records/18879016 - Non-Singular Black Hole Interiors – Gravitational Collapse Resolved as Geometric Necessity Under the Distinction Axiom 33. https://zenodo.org/records/18880455 -The Articulation of Distinction: Why Mathematics Describes Reality with Unreasonable Effectiveness 34. https://zenodo.org/records/18880897 -Birth of Consciousness and the Phenomenology of Distinction: Subjective Experience as Self-Referential Registration 35. https://zenodo.org/records/18884555 -CMB Large-Scale Anomalies as Geometric Inevitabilities: Fragmentation Signatures of the Cosmological Pangaea Initial State 36. https://zenodo.org/records/18891292 -The Black Hole Information Paradox and Emergent Holography under the Distinction Axiom 37. https://zenodo.org/records/18891625 -Primordial Nucleosynthesis in a Finite Initial State: Resolving the Cosmological Lithium Problem via Quantum Bounce and Entropic Dynamics 38. https://zenodo.org/records/18891904 -Quantum Measurement and the Emergence of Observers: Born Rule and Decoherence from Distinction Registration and Entropy Gradients in Cosmological Pangaea 39. https://zenodo.org/records/18892666 -Large-Scale Structure Power Spectrum and Baryon Acoustic Oscillations in the Navigable Universe 40. ht