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1 year agoThis is a pretty difficult question to answer since all phenomena are quantum. A star is powered by nuclear (quantum) fusion. Permanent magnets depend on the quantized angular momentum of electrons. Could these phenomena be allowed by something other than quantum mechanics? Maybe. But a constant goal of science is to find the simplest explanation for all we observe, meaning that whatever alternative explanations you come up with, should they be correct, then taking them all together will constitute a theory that at least looks an awful lot like matter waves (mathematically, at least).
It’s not really communication. They ‘know’ because they become part of the same wave function. The wave function of the system is
|psi1 psi2> ± |psi2 psi1>
Note that if the ± is a plus, then exchanging psi1 and psi2 yields the exact same equation. If it’s a minus, you get a negative sign out front. Electron systems have a negative sign because of the spin statistics theorem (I don’t understand that part, so you can look it up if you want—it involves field theory iirc) Now, if electrons are exactly the same (indistinguishable), then exchanging them will yield the exact same wave function, leading to
|psi1 psi2> - |psi2 psi1> = |psi2 psi1> - |psi1 psi2>
The only solution here is |psi1 psi2> - |psi2 psi1> = 0
But recall that |psi1 psi2> - |psi2 psi1> describes the system as a whole. So this system is prohibited by quantum mechanics, and there’s no way for two electrons to have indistinguishable states (be in the same place at the same time).