ISO and the Cosmic Dark Ages: An Observational Programme

Abstract

The geometric-invariant reading of the fine structure constant (companion paper) makes one epoch of cosmic history special with no adjustable parameter: the moment the universe's logarithmic extent L_θ swept through the invariant 1/α = 4π³ + π² + π. We compute that epoch from the invariant and standard cosmology alone — horizon ℓ_P·e^(1/α) = 5.3 × 10²⁴ m, t = 186 Myr, z = 19.5 — placing the predicted 21cm signature at an observed frequency of 69.4 MHz, ground-accessible now. The coordinate coincides with the high-redshift onset edge of the contested EDGES absorption profile (z ≈ 19.7, 68.5 MHz) to Δz ≈ 0.3. We lay out the observational programme: derived quantities (epoch, frequency); the computed profile from the coupling companion paper (sign, width, amplitude −475 mK at z = 17.2); an instrument map from current ground spectrometers (EDGES, SARAS, REACH, MIST, PRIZM, LEDA, HERA, SKA-Low) to lunar arrays (LuSEE-Night); explicit falsification criteria including the three possible arbitration outcomes; and a built-in control: the pre-crossing dark-ages spectrum below ~46 MHz is predicted standard. All numbers are generated by the archived script.