A Dark-Ages 21-cm Power-Spectrum Forecast for a Lunar Far-Side Array

The dark-ages power spectrum — fluctuations in the absorption signal before any stars formed — is a long-term goal of low-frequency radio astronomy, accessible in practice only from the lunar far side or from space, where terrestrial interference and the ionosphere are absent. Using the stated cosmology and the brightness-temperature relations described in the Methods, the calculation gives the following headline values: z = 80; power mK2 = 85; signal mK = -67; freq MHz = 17.5. The comparison values taken from the published record — including the EDGES and SARAS reports, HERA limits and the Planck optical depth where relevant — are used exactly as published, and the bounce contribution enters only through the named timing, heating or shear inputs. The result is a computed prediction for the delayed-onset history, with its sensitivity to each input stated in the Discussion. This study is simulated and computed from stated assumptions; it is not a measurement.