The Ceiling on the Spiral: The Outward Side of the Nesting Ladder

The nesting ladder of this series has an inward side of four rungs — atom, nucleus, stellar core, black hole — each a distinct physics, and a single outward rung, the cosmic de Sitter ceiling. This paper asks whether the outward side is a matching ladder and answers no: it is one mechanism, dark energy. "Many horizons, one height" holds only relationally and within one epoch — each observer at the centre of their own Gibbons–Hawking horizon, all the same height because Λ is homogeneous (import). The content is where "one height" breaks: across epochs the ceiling has risen ~100 orders of magnitude from the inflationary de Sitter horizon to today's ~10^122, and it may be moving now — DESI DR2's ~4.2σ lean toward evolving dark energy is a direct test, with quintessence removing any fixed ceiling and phantom collapsing the horizon in a Big Rip. As a qualification to the entropy paper's claim that the second law "asymptotically pins λ to its de Sitter value," the pinning is shown to be conditional on Λ being constant; evolving dark energy un-pins the outward λ. The lens fixes no number and predicts nothing. The verdict: the outward side clarifies less than the inward side, exactly as the series' meta-principle predicts. The parent cosmology's falsification record is reprinted.