@ibyghee Earth’s core, a rotating mix of iron and nickel with internal flows driven by the passage of heat, has no battery and no wires. Instead, it creates magnetism by means of self-sustaining feedback. Liquid metal moving through a magnetic field generates a current, similar to that induced in the moving coil of an electric generator. That current in turn generates the magnetic field. This “self-generation” mechanism can dramatically amplify the small, random fields that always exist in magnetic materials. To do this, though, the flow must be both complex, mixing up the longitudinal and latitudinal directions, and rapid, “tangling up” magnetic field lines faster than they can untangle.
