64 lines
3.2 KiB
Markdown
64 lines
3.2 KiB
Markdown
# Aetheria gravity: target
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Campaign `aetheria-gravity`. Opened 2026-10-14 on operator ruling
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`aetheria-release:ruling:gravity-honest-wells-agreed`. Its invariants,
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not-in-scope list and canonical implementations are the typed target
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`aetheria-gravity:target:r1`; this page keeps the rationale.
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## Why
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The orbit probe (`docs/research/2026-10-13-orbit-probe/report.md`) measured
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today's wells against the real code:
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- The heightfield is not a potential. Each well is a positive core plus an
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equal negative-density ring (antimass) out to its rim, so it is
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mass-neutral and nothing is felt outside the rim.
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- The force is `S*R*|grad h|^2` behind a slope gate (`|n_xz|^2 > 0.001`),
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which zeroes it in every core, at every rim, and in every zone bowl wider
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than about 3117 units.
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- The outer half of every well has unstable circular orbits, and about 40%
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of moons sit there.
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- The wells pull 20 to 70 times harder than the OrbitPeriod rail implies, so
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holding a rail orbit costs a real fraction of a ship's thrust.
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The operator's frame (2026-10-13): bodies sit above the grid so there is always
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room to fly beneath them, so being within a sun's radius is not being inside
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it; gravity is shaped that way on purpose, and the picture is why it looks as
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it does. "We can use correct wells and simply exaggerate the height."
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## The shape
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One scalar potential per zone owns gravity. Each body contributes a 2D
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point-mass well: logarithmic potential and force falling as 1/r outside the
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body's radius, softened inside it (force linear to zero at the centre, matched
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in value and slope at the radius, Plummer-like). Wells add. Force is the
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potential's gradient, with no gate. The drawn height is the potential times one
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exaggeration factor, so what the player sees and what the ship feels are the
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same function. With a 1/r tail every circular orbit is stable.
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Ink zones are not under this law. Their pillars stand where suns would
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(`aetheria-fauna:ruling:ink-pillars-are-suns`), but the Ink need not obey
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flatspace gravity: the operator sketched a pillar as a negative-gravity
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singularity with a bowl around it, a Bundt tin, plus a swell ships feel
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(`aetheria-fauna:ruling:ships-feel-swell`). That law is
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`aetheria-release:follow_up:ink-gravity-law`, and it plugs into the potential
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owner this campaign builds.
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## Rulings of 2026-10-14
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The forks the first Imagination pass raised were ruled the same day
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(`aetheria-gravity:ruling:*-ruled`): the field owns the orbits; gravity starts
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at about 0.5 u/s^2 at a median planet's orbit; pull comes from mass through an
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authored compressed curve; children are placed within their parent's reach;
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each well's soft core has its own authored radius and never levels the field
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out where bodies orbit; one global exaggeration; the grid's height carries
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gravity only, and the wormholes' presentation is provisional; ships feel only
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the potential. The flatspace bowl and ripples are deleted, not disabled: the
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map found them live in `Settings.asset` and `Zone.GetHeight`. The model page and
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body facts are in `docs/aetheria-gravity-map.md`.
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## Not here
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Portals and portal gravity, and non-Euclidean zone geometry, belong to the
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pseudospace-flavours line (`aetheria-release:follow_up:portals-and-portal-gravity`,
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`aetheria-release:follow_up:pseudospace-geometry-owner`).
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