this post was submitted on 21 Dec 2024
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Not that I know much about this, but the Pauli principal always struck me as an observation rather than anything like an explanation. As an explanation it's extremely unsatisfying. "Why won't electrons occupy the same space?" "Well.. because of the Pauli principal". No.. that's not the reason, that's just restating what we observe. Glad to see physicists find it weird too (as is suggested in the comic)
It's a lot more complicated than that even.
Pauli Exclusion Principal is that two or more identical particles of half integer spin cannot occupy the same quantum state. So two electrons in an orbital must be made of a +1/2 and -1/2 spin. This is evidenced by observation, but the prediction was made long before that.
This is because the total wave function for fermions is antisymmetric (bosons, like the photon, are symmetric). It's sort of hard to describe how this works without paper and pen, but essentially there is different formula of solving a wave function. A symmetric wave function is a sum, and an antisymmetric wave function is a difference. The issue arises when you have two identical particles - symmetric functions can be any state as it results in a solution >0. If you have an assymetric function of two identical particles, the result is 0, which isn't a valid state.
The very uncomfortable part of physics is here: when we ask "why" the answer based on the math and the observation is quite literally "because that is the way math works." It's fundamental - just like x * 0 = 0.
But it's an outlier right? I guess that's why it's joked as an additional force in the comic, because even by "maths just describes reality" standards, it's weird. Like, it feels like a particle "knows" if the state is already occupied, and that's why it can't occupy it. But that implies some communication - the conveying of some force - else how does it "know"?
The math is describing reality - but that's why I highlighted that the math predicted it long before there was experimental evidence.
From what we know about the quantum realm (my physics professor liked using that description, as if it's a whole different existence), it appears that it's actually the opposite: reality is obeying the math. Consider how wild that is - particle interactions are doing what they do because of how mathematics works. Something that we humans came up with to describe observations.