Quantum Particles Aren’t Spinning. So Where Does Their Spin Come From?
scientificamerican.com
scientificamerican.com
My impression is that someone theorised something being caused by an electron spinning but realised that the electron would have to spin faster than the speed of light and so that theory is no good and then … somehow … jumped to the conclusion that electrons can’t spin.
1. Electrons are point particles. "Spin" in the usual sense requires a center and an edge. Electrons don't have that.
2. Electron angular momentum is quantized. All electrons have exactly the same amount. That's not how regular "spinning" works, where the angular momentum is radius times speed, and speed can be any value. And in particular, it can't be zero; there is no such thing as a spin-less electron.
There is a "classical electron radius" which can be derived in non-quantum terms from how much energy it would take to "make" an electron by bringing bits of abstract "charge" together. It doesn't figure into QM; it's just a useful shorthand for looking (classically) at how light interacts with them.
You can also run that radius through the angular momentum exercise... but all that tells you is that something funny is going on with electron spin. But you already knew that from the other things I cited, so it's good only for high school classes and pop-science articles.
However,…, I can’t help but feel that your explanation is assuming the correctness of a certain theory of quantum physics that - while it may be well supported - in itself doesn’t rule out the possibility that electrons might spin.
However, I certainly don’t want to get into an argument about quantum physics that I don’t know about.
I am confused because the start of the article said that electrons appear to spin but doesn’t describe why they appear to spin. Is it because they have a negative charge? Is it because they have a magnetic field?
I think perhaps the problem is that the article of this post was talking about theories from 1925 that - and I am reasonably confident about this - pre-date theories of quantum physics. They talk about the other two physicists trying to decipher what Wolfgang Pauli meant. Why did no-one ask him? Did he die?
My reading of the article is that Pauli had allowed for a parameter related to what the others assumed to be electron spin. That seems pretty reasonable when so many things in physics relate to things spinning or orbiting around other things…
But if electrons don’t “physically” spin. What is spin.
Supposedly entangled electrons have the same spin - so what is it that is the same?
Also, why do you claim an electron is a point particle? Is it just because quantum physics treats it as a point particle? What is a point particle anyway? Is there some sort of cyclic definition where a point particle is something that is like an electron?
Anyway, I hope I’m not antagonising you (and others). Physics is just something I find very interesting but I’ve realised I’ll never have the time to study it seriously.