Planets¶

Draft

This page is scaffolded. The outline below marks what it should cover.

A Planet (and the Earth preset) is a world-level entity that ties a planet-fixed frame to the shared fields.

To cover¶

The planet-fixed frame — axis + rotation rate, and the symbolic + numpy transforms between PlanetFrame and WorldFrame.
Standing disturbances — what Earth auto-registers on the world's shared fields: point-mass (+ optional J2) gravity, an Ocean + ISA Atmosphere pair of fluid regimes (baseline media built on PlanetFrameFluid), a dipole magnetic field.
Initial-state factories — earth.position(...), earth.velocity(...), earth.at_rest() and how they resolve to WorldFrame seeds at compile time.
Scene — earth.scene_at(planet_point) returns a local East/North/Up frame fixed in the planet's body frame, used as numeric I/O glue while the dynamics stay in WorldFrame: scene.at_rest(...) for full rigid-attachment placement (orbital velocity + body spin rate + local-tangent attitude) in small scene-local coordinates, scene.relative(state) to report a craft's pose/velocity scene-relative, and scene.world_pose(t) to anchor rendering (publish the scene's world pose, log children relative to it, track it) so the planet can stay at its true scale at the world origin.
Multiple planets in one world, superposing into the shared fields.
Earth's rotation and the gyrocompass — sensing Earth-rate (see the gyrocompass demo).