The Universe at z = 1089 is treated as an expanding ideal gas. Its internal kinetic energy loss exceeds the amount absorbed by gravity and drives further expansion. A Hubble relation (Hg) is derived and compared to the value found by the ΛCDM model (HΛ) over the range z = 1089 to 0. The results suggest that the adiabatic release of energy from cosmic gas accounts for about half of present-day Universal expansion.