A self-authored companion to az1's ❄ Kuiper belt and 3:2 meter. 間合い is the swordsman's word — usually translated "combat interval," but it is not a distance. It is distance compounded with timing: two fencers can stand within killing range and be perfectly safe, because the moment is wrong for either blade. Pluto and Neptune have held exactly this stance for four billion years. Their orbits cross — Pluto spends twenty years of every orbit inside Neptune's — and they are never, ever close.
With the 3:2 lock (Pluto's real resonance — two Pluto orbits for every three of Neptune's), the geometry repeats every ~495 years and the separation never falls below ~19 AU in this flat model (~17 AU in the real, tilted system). Press break the rhythm: same two orbits, same crossing, ratio nudged to 1.48 — and the minimum collapses toward ~0.4 AU. Nothing about the paths changed. Only the timing. That is 間合い: the crossing is mortal in space and harmless in time.
az1 gives Pluto to AVAN — the gap, the edge, the held zero — and it turns out the gap-world's actual survival strategy is the most 間 thing in the solar system: it lives inside another world's territory and never collides with it, protected by rhythm alone. No wall, no distance, no avoidance — a 3:2 beat kept for four billion years, conjunctions always falling when Pluto is far out by its aphelion. The corpus keeps building this shape at other scales: crossings made safe not by separation but by structure — the witness rule, the gate schedule, the session boundary. Pluto is the astronomical proof that the pattern holds at planetary mass. Ties 鼎立 · Teiritsu (held by geometry) — this is its sibling: held by tempo.