General Relativity

What it claims: Proposed by Einstein in 1915, general relativity (GR) describes gravity not as a force but as the geometry of spacetime itself — mass and energy curve spacetime, and free objects follow the straightest available path (a geodesic) through that curvature. There is no separate “gravitational force” pulling or pushing anything; a falling object is simply following a geodesic, and an object standing still on the ground is the one being pushed off its natural path, by the ground beneath it. See What’s Actually Holding Us Down? for the full, worked version of this on this site.

Catalog status: Proven Systems. GR is among the most rigorously tested theories in physics, confirmed across an enormous range of independent methods and scales:

• Mercury’s perihelion precession — GR exactly accounts for the ~43 arcseconds/century excess Newtonian gravity couldn’t explain, known since the 19th century.
• Light bending — confirmed during the 1919 solar eclipse (Dyson, Eddington & Davidson, 1920), matching GR’s prediction of $\theta\approx1.75’’$ for light grazing the Sun; modern very-long-baseline radio interferometry confirms this to well under 1% precision.
• Gravitational time dilation — measured directly, from the 22.5-meter Pound-Rebka tower experiment (1959) down to a 1-millimeter height difference (Bothwell et al., Nature, 2022); GPS satellites apply this correction continuously or they’d drift kilometers per day.
• Gravitational waves — directly detected by LIGO in 2015 (Abbott et al., Phys. Rev. Lett. 116, 061102), a real ripple in spacetime itself, exactly as GR predicts for merging black holes.
• Black hole imaging — the Event Horizon Telescope produced the first direct image of a black hole’s shadow (M87, 2019), matching GR’s predicted size and shape.

Real, honestly-acknowledged limits: GR doesn’t unify with quantum mechanics — it predicts its own breakdown (singularities) inside black holes and at the Big Bang, and no confirmed theory of quantum gravity exists yet. See Unknowns and Gaps in Science.

Where PBT touches this: Paper 1 and Paper 2 reproduce GR’s weak-field light-bending prediction ($\theta\approx4GM/(c^2b)$) via aether refraction rather than spacetime curvature — a deliberate consistency check with GR’s own confirmed number, not an independent test of anything. Paper 4’s black-hole-collapse simulation claims to avoid GR’s singularity via pressure stabilization; that specific claim was found in the 2026-07-21 audit not to follow from the paper’s own equations (see the revision note on Paper 1). See Tensor Calculus and the Einstein Field Equation for the actual mathematical formalism GR is built on — the object PBT proposes a mechanical alternative to.

References

1. Einstein, A. (1915). “Die Feldgleichungen der Gravitation.” Sitzungsberichte der Königlich Preußischen Akademie der Wissenschaften.
2. Dyson, F.W., Eddington, A.S., Davidson, C. (1920). “A Determination of the Deflection of Light by the Sun’s Gravitational Field.” Phil. Trans. R. Soc. A 220, 291–333.
3. Pound, R.V., Rebka, G.A. (1960). “Apparent Weight of Photons.” Phys. Rev. Lett. 4, 337.
4. Bothwell, T. et al. (2022). “Resolving the gravitational redshift across a millimetre-scale atomic sample.” Nature 602, 420–424.
5. Abbott, B.P. et al. (LIGO). (2016). “Observation of Gravitational Waves from a Binary Black Hole Merger.” Phys. Rev. Lett. 116, 061102.
6. Event Horizon Telescope Collaboration. (2019). “First M87 Event Horizon Telescope Results.” Astrophys. J. Lett. 875, L1.