Eli5 The earth has a magnetic field, including because of the metal core, but magnets are demagnetized at high temperature. How is this possible
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Magnetic fields are generated by charged particles with angular momentum. Angular momentum comes from two different places.
1. Orbital angular momentum, which arises when a particle moves in a loop.
2. Spin angular momentum. This is a quantum property of particles which is intrinsic and depends on the kind of particle.
Permanent magnets (like cobalt) arise when all of the particles in a metal’s spin angular momentum line up with each other, creating a large net angular momentum and therefore magnetic field (dipole moment). When the temperature is high, all the spins jiggle around in random directions, and they cancel each other out, destroying the magnetism. The Earth does not work like this. It’s magnetic field arises because of orbital angular momentum – the Earth is spinning, as are all of the charged particles in the mantle, giving a large magnetic field.
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