Editing Openai/6897769e-4ee4-800f-aba5-69cca34f701c (section)

==== 1. Thomson + interplanetary / ISM - Thomson × interplanetary (5×10¹⁵) → δ∼3×10−13\delta\sim 3\times10^{-13}δ∼3×10−13: tiny. - Thomson × diffuse ISM (1×10²⁰) → δ∼7×10−9\delta\sim 7\times10^{-9}δ∼7×10−9: still tiny. Interpretation: free-electron Thomson scattering in low-density plasmas cannot produce anything near gravitational redshift magnitudes. ====
# Thomson + atmosphere-effective (1×10²³) - Gives δ∼6.7×10−6\delta\sim 6.7\times10^{-6}δ∼6.7×10−6 (notice this is comparable to solar photospheric GR potential ~2×10⁻⁶ but many orders larger than Earth's surface GR 6.95×10⁻¹⁰). But this is misleading: Thomson applies to free electrons (plasma). The neutral atmospheric molecules (N₂, O₂) at optical frequencies do not behave like free electrons and have much smaller scattering/absorption cross sections averaged over a broadband spectrum. So using σ_T here is not physically correct; the effective σ for neutral air averaged over the ambient spectrum is far, far smaller. Therefore the Thomson+atmosphere number is not a realistic prediction.
# Resonance / large line cross-sections - These can produce large deltas against sufficiently large columns — but they are narrow-band, and the huge numbers in the table come from assuming the entire ambient photon bath sits at that resonant frequency. Real spectra do not concentrate all photon power exactly at a narrow resonance. When you weight by the real radiation field and by the line's profile (and remember Kramers-Kronig relations), typical broadband effective σ averaged over the photon field is much smaller than the line peak. - In other words: strong lines can locally dominate the coupling for those exact frequencies, but the integrated effect on the full event rate (which sums over all frequencies) is usually small unless you are in a highly line-dominated plasma tuned to that transition.
# Photosphere-like columns (1×10²⁸) - Multiplying even Thomson by such a massive column gives δ ~ 0.67 — i.e. huge effect — but this scenario implicitly counts every electron in a dense stellar layer as an independent free scatterer affecting the external event rate all the way to infinity. In practice, stellar photospheres are opaque and the simple integrated-column model breaks down: many photons are thermalized locally and radiative transfer/opacity effects must be treated with full radiative-transfer physics. So the raw large number is not a realistic indicator that Thomson scattering "explains" gravity — it's just the product of extreme column × cross section.