The Two Constraints

4.1 — Propagation constraint: c

Claim L1 (Established). c = 299,792,458 m/s defines the null-cone structure of spacetime. Photons follow null geodesics (ds² = 0) with dτ = 0. No inertial rest frame for massless particles. [Layer 1]

4.2 — Compression constraint: ρₚ

Claim L2 (Established). The Planck density ρₚ = c⁵/(ℏG²) ≈ 5.16 × 10⁹⁶ kg/m³ is the natural density scale where quantum gravity is expected to dominate. [Layer 1]

4.3 — Inverse relationship

Claim L3 (Dimensional fact + interpretation). Planck units show c, G, ℏ co-define the quantum-gravity regime. ℓₚ/tₚ = c demonstrates dimensional coupling. Necessary but not sufficient for ontological equivalence. [Layer 1: dimensional fact. Layer 3: interpretation.]