From Wikipedia:
Epicyclic gearing or planetary gearing is a gear system consisting of one or more outer gears, or planet gears, revolving about a central, or sun gear. … Epicyclic gearing systems also incorporate the use of an outer ring gear or annulus, which meshes with the planet gears.
Use the menu in the top-left to change the frame of reference, fixing the specified gear in-place.
forked from mbostock‘s block: Epicyclic Gearing