2 ms·
> elementary particles have no defined size in QM That's only kinda-sorta true, and only in a very restricted sense. All particles have a wavelength, but that
by jiggawatts 3y ago
> elementary particles have no defined size in QM
That's only kinda-sorta true, and only in a very restricted sense.
All particles have a wavelength, but that can change depending on their velocity.
In QM models, it is a simplification to treat particle as point-like to make the mathematics tractable. It isn't necessarily an accurate picture of the underlying reality.
> QM spin is not a rotation speed of any kind; QM particles are not little balls rotating around their center; quantum spin has no known relation to the speed of light
That's not exactly the case. From my best understanding, Spin is just the Dirac Belt Trick, an indication that particles are part of the spacetime fabric and attached to it. When they rotate, the fabric rotates with them locally. This requires two full rotations (720 degrees) to go back to the original state, which is why you have "spin 1/2" and the complicated maths.
Two good visualisations are here: https://youtu.be/LLw3BaliDUQ https://youtu.be/LLw3BaliDUQ
and: https://youtu.be/jdVoFr5d4Rw https://youtu.be/jdVoFr5d4Rw
- simiones 3y ago> In QM models, it is a simplification to treat particle as point-like to make the mathematics tractable. It isn't necessarily an accurate picture of the underlying reality. As far as I understand, it is more than that: it is an explicit assumption of the theory that elementary particles do not have an internal structure, and so their radius must be 0. This is not to be confused with the wave-like representation, which of course does have a size in space. On the spin question, I will not claim I understand enough to actually go into more detail than the (probably simplistic) observation I've read that quantum spin can't be understood in terms of classical rotation/movement.