Gas Temperature at Cosmic Dawn: Adiabatic Cooling with a Bounded Bounce Contribution

How cold was the gas when the first stars formed? The answer sets the maximum possible depth of the absorption signal and the starting point for all heating calculations. Using the stated cosmology and the brightness-temperature relations described in the Methods, the calculation gives the following headline values: Tg adiab K = 5.8; Tcmb K = 49.1; max bounce add K = 2.0; total max K = 7.8. 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.