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> they found hidden patterns of magnetic charges within hematite, including monopoles, dipoles and quadrupoles. I appreciate the context on "monopoles" in this

• pbmonster 3y ago
  The wiki on this topic is not to bad [0]. Essentially, it's a configuration of 2 south poles and 2 north poles. It's pretty important if you're doing quantitative magnetism. Many magnetic configurations don't generate a pure dipole-like field, but also need higher order contributions - like quadrupole and octopole moment - if you want to model/calculate the field. Quadrupoles also have useful technical properties, you can use one to re-focus the beam in a particle accelerator, for example. In a sense, they act like magnetic lenses. [0] https://en.wikipedia.org/wiki/Quadrupole https://en.wikipedia.org/wiki/Quadrupole
  • eszed 3y ago
    Thanks. I looked at that, but I don't have the maths background to follow the real explanation. I get the four bar magnets or four coils stuck together, as an example of the charge state, but that looks simplified to the point that it's maybe not real. I think I'm trying to bridge a gap in my understanding between "this is a convenient way to refer to a complex interaction between multiple magnetic fields", and "this is a object (constructed? naturally occurring?) that I can hold in my hand". Or, maybe that's not even a reasonable mental model / distinction - magnetics be freaky.