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  • Magnets can be created by running currents through wires, finding a suitable material

  • that naturally has all the magnetic fields of its atoms aligned, or forcing the magnetic

  • fields of atoms to align.

  • But there's one more kind of magnetism that all materials exhibit, even those whose constituent

  • atoms aren't magnetic - though it's so weak that the other kinds of magnetism often overwhelm

  • it. Basically, an external magnetic field causes the electrons around atoms in a material

  • to change course, and their new motion generates an opposing magnetic field. This field is

  • pretty weak, but it does cause the material to be repulsed from the magnet a little bit

  • - for example, if you hang a wooden toothpick in a magnetic field, the ends will repel the

  • field and it will end up aligning across the magnetic field. This is a convenient way to

  • remember the name of this kind of magnetism - diamagnetism - since "dia" means across,

  • like the "diameter" measured across a circle. Diamagnetic materials will repel a magnet,

  • and a diamagnetic "compass" will point across the magnetic field - that is, it will orient

  • east/west.

  • As weak as it is, diamagnetism is pretty darn awesome because it's a repulsive effect: any

  • diamagnetic material will levitate in a strong enough magnetic field! Like this chunk of

  • graphene, or, since water is diamagnetic, this frog. In principle, humans could also

  • be levitated this way, though the magnetic fields required would be enormous.

  • There are also a lot of subtleties we've skated over, like the fact that nitrogen is diamagnetic

  • even though as an atom it has unpaired electrons - one might think that it *should* be at the

  • very least paramagnetic. But nitrogen atoms bond to form N2 molecules which have full

  • outer electron shells and are thus only diamagnetic. On the other hand, molecular O2, as we've

  • seen, still has unpaired electrons, and it's paramagnetic.

  • You've probably also seen how superconductors can levitate in a magnetic field, which is

  • a kind of perfect diamagnetism - not only do the currents in a superconductor create

  • opposing magnetic fields, they expel magnetic fields from the material entirely. But the

  • root cause is very very different, and that's a journey for another day.

Magnets can be created by running currents through wires, finding a suitable material

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