Experimental Validation of the Dx Energy-Shadow Cone Geometry Using Superconducting Gravimeter Data from Multiple Independent Stations

The Earth’s gravitational field undergoes systematic periodic modulation arising from interference between the Sun and Moon shadow cone zones. We present evidence for the Dx-Factor vortex— a previously unknown gravitational phenomenon with 29.53-day lunar synodic periodicity confirmed across six globally distributed superconducting gravimeter stations spanning 83° of latitude (60.2°N to 32.4°S). Analysis of 25+ years of IGETS Level 3 residual data yields 544 detected gravitational peaks across three primary validation stations on three continents. All three stations independently confirm the 29.53-day periodicity at extraordinary statistical confidence: Membach (50.6°N, Belgium) p ≈ 10⁻¹¹⁵; Medicina (44.5°N, Italy) p = 2.8×10⁻¹²⁴; Sutherland (32.4°S, South Africa) p = 3.0×10⁻⁶¹; combined p ≈ 10⁻³⁰⁰. The vortex arises from geometric interference between the Sun and Moon shadow cones, whose apices sit at Earth’s centre and whose bases expand across Earth’s surface. The gravitational anomaly is governed by: Δg(φ,Ψ) = A₀ × W(φ) × cos²(Ψ), where A₀ ≈ 300 nGal is the intrinsic amplitude, W(φ) is the dimensionless 1-minute measurement efficiency factor of IGETS instruments (not an intrinsic vortex property), and cos²(Ψ) is the cone-rim interference term (Ψ = lunar phase angle), producing equal peaks at New Moon and Full Moon (Ψ = 0° and 180°) and negative troughs at quadrature (Ψ = 90° and 270°). The vortex ring radius follows R(Ψ) = R₀ × sin(2Ψ) with R₀ ≈ 80°, reaching maximum size at Ψ = 45°. Epoch-folded analysis of 773 lunar cycles across four stations reveals that the ascending rim-crossing phase angle scales linearly with vortex core diameter at 0.56°/km (r² = 0.9985), confirming the ring expansion geometry. Metsahovi (60.2°N) exhibits a bimodal timing distribution with peaks at Ψ ≈ 24° (ascending) and Ψ ≈ 65° (descending), predicted by the ring model to within 0.6°. A universal gravitational energy diffusion coefficient K₀ = (2.816 ± 0.165) × 10⁷ m²/s is confirmed across all six stations to within 5.85%, with no station-specific fitting parameters. The Cibinong station (6.49°S, Indonesia) is predicted to show δg = 308.7 nGal as an immediate, falsifiable test from the existing IGETS archive. The discovery establishes: (1) the first observational evidence for gravitational shadow cone interference at Earth’s surface; (2) a complete predictive model explaining timing, amplitude, and sign at all six stations; (3) a new planetary habitability criterion — the Moon-Sun angular diameter ratio of 0.971 (within 3% of unity) is unique in the solar system; and (4) five falsifiable predictions for community validation, including single-event detection at equatorial stations using 1-second gravimeter data.