ashes. This paper joins both assumptions in a single question — and answers it with a machine. In the bounded cosmology established in prior work, the universe is a gravastar interior: a shell at R = 4.4×10²⁶ m, threaded by the neck of the Unified Hourglass gravastar, immersed in the water-matrix lattice. This paper identifies the working substance of that machine: helium. A single gaseous torus of helium on the cold exterior of the shell — one ring, not two; the doubling seen from inside is the projection of the one — feeds inward through the neck's reduction conditions, where the black-hole physics are real, and establishes both the temperature floor of the bounded system and the pressure environment within which all interior matter is buoyant. Six results follow. First, the shell equilibrium computed from stellar luminosity and geometry alone returns 2.72 K against the measured 2.7255 K of the cosmic microwave background — agreement to 0.2 percent. Second, the lambda transition of helium-4 at 2.17 K sets the floor beneath the equilibrium; the measured temperature sits 0.55 K above it, the signature of a regulated bath. Third, the latent heat capacity of the cosmological helium inventory, 7.6×10⁵⁷ J, equals roughly thirty years of the combined output of every star — the cold is not scarce; it is structural. Fourth, the breathing of the shell operates as a thermodynamic cycle in which every stage cools, because the system runs forty kelvin below helium's inversion temperature, and the boundary displacement at which the cycle functions is fixed by the Israel junction conditions — the shell cannot sit elsewhere. Fifth, buoyancy mechanics is developed as the interior force law: displacement replaces attraction, orbits become equilibrium depth layers, and flat rotation curves follow without dark matter, with a falsifiable exponent prediction for void galaxies. Sixth, the abundance ladder of hydrogen, helium, and water is read as the composition of the medium itself. Every calculation can be verified by pencil and paper. The predictions are stated where they can fail in public.

arXiv:2609.29324 · cs.CG