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diamagnetism, paramagnetism and ferromagnetism can be fully explained only using quantum theory

The magnetic properties of certain materials (e.g. why an unmagnetized piece of iron sticks to a magnet of either polarization), the way permanent magnets work, is best explained by quantum mechanics.

However, the electromagnetic force itself doesn’t “arise” from quantum mechanics, and you can explain things like electromagnets quite will without considering quantum mechanics.

Usually you take the “classical” formula for a force and to inform your quantum mechanical model of particles, and that’s how you can arrive at things like deriving how permanent magnets work with the help of w quantum mechanics.

Generally, a lot of material science and chemistry is inherently quantum mechanical because the way atomic orbitals and molecular bonds work is heavily quantum mechanical.

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webghost0101@sopuli.xyz ⁨1⁩ ⁨day⁩ ago
Thanks for a we written reply.

Though i still dont quite get this

the electromagnetic force itself doesn’t “arise” from quantum mechanics, and you can explain things like electromagnets and a lot of common electric circuits (until you need a transistor) quite well without considering quantum mechanics.

You seen to say if we can explain x without y then y cannot be fundamental to x.

But can electromagnetism at all emerge if the quantum mechanics dont exist to emerge things like magnetism and some of the behavior of electrons?

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- WolfLink@sh.itjust.works ⁨16⁩ ⁨hours⁩ ago
  
  But can electromagnetism at all emerge if the quantum mechanics dont exist to emerge things like magnetism and some of the behavior of electrons?
  
  Short answer: yes.
  
  Technically the world can’t exist without all of its physics. But that’s kinda backwards from how you study it. Quantum mechanics isn’t “more correct” than classical mechanics, it’s more that it’s “more detailed”.
  
  If you want to model an electromagnet, an electronic circuit, light (in most macroscopic situations), how permanent magnets interact, electrostatic situations like how static electricity makes your hair stand up, lightning, the magnetic fields of celestial bodies like the Earth and Sun (they are big electromagnets), etc. you will use “classical” electromagnetism (meaning Newton’s mechanics, possibly with Einstein’s modifications, and Maxwell’s equations).
  
  If you want to model material science situations, like determining what material to make a diode or transistor out of, or if a given material can become a permanent magnet, you will likely need quantum mechanics to help model the interactions of electrons on the atomic scale. The section on Wikipedia you were looking at is about this kind of material science. You do this by combining the same “classical electromagnetic” equations with Schrödinger’s equations for quantum mechanics.
  
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- Zink@programming.dev ⁨1⁩ ⁨day⁩ ago
  
  But can electromagnetism at all emerge if the quantum mechanics dont exist to emerge things like magnetism and some of the behavior of electrons?
  
  Well yeah, sure. Earlier you said something like “electromagentism is caused by quantum phenomena,” but you can say that about almost every object and behavior in the universe! We don’t have a theory of everything but the standard model and quantum field theory explain a lot.
  
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  - webghost0101@sopuli.xyz ⁨1⁩ ⁨day⁩ ago
    “Caused” was not a good term but like i said i made that comment half jokingly
    
    I find that almost everything can be boiled down to just be a display of quantum mechanics which is why id place it as more fundamental.
    
    I cant really say that about gravity/spacetime though. Maybe someday we do find that it also is but for now it seems to be distinct.
    
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