PBT: Light

Light in PBT bends via refraction through density gradients in the medium, rather than spacetime curvature — deliberately built to match GR’s weak-field prediction ($\theta \approx 4GM/(c^2b) \approx 1.75’’$ for the Sun) rather than diverge from it. That bending result is a consistency check with GR, not a point of difference (see Paper 2).

Separately, the site’s interpretive framing treats the same particle medium (see Pressure) as what light and radio waves propagate through — a mechanical-wave picture, not empty-space propagation with no medium. That medium-carries-light claim is not yet a derived consequence of Paper 2’s published action, which has no photon–medium coupling term. Adding a real coupling, then clearing modern photon-isotropy bounds, is open research — not established mechanism on this page. A first candidate coupling now exists as research, not adopted: see Paper 2’s Candidate Light-Sector Extension.

One real consequence worth naming: the bending described above comes from the gravitational metric term already in Paper 2’s action, not from any formal coupling between light and the aether field $u^\mu$ — that coupling is the separate, still-missing piece discussed above. In the absence of any specified electromagnetic sector, the default assumption is ordinary, unmodified Lorentz-covariant electrodynamics, the same physics any theory inherits when it hasn’t touched that sector. On that assumption alone, the theory is automatically consistent with the Fresnel drag coefficient for light in a moving transparent medium ($f=1-1/n^2$, matching Fizeau’s 1851 measurement) via standard relativistic velocity addition, given only the medium’s own measured refractive index — a real, 175-year-old result, not a new PBT prediction, and not evidence for the still-open medium-coupling question above.

Covered in: Paper 2 (light-bending derivation / GR analog), Paper 12 (summary equation), Pressure (medium ontology and framing). See also What Would Actually Distinguish PBT From General Relativity.