

all 11 comments

[–]gebkbk69 1 point2 points  (5 children)

So, is it, or is not true that "Spin" is the angular momentum of circulating currents or not?

[–]eyeofthephysics 2 points3 points  (4 children)

The intrinsic magnetic moment of particles is not caused by circulating currents, but it behaves as if it were caused by circulating currents (as opposed to being caused by two monopoles).

[–]gebkbk69 1 point2 points  (3 children)

Isn't all of particle physics just, "It behaves as if ....". For example, a photon behaves as if it is a particle and a wave depending on which measurements you make. The theory doesn't really reconcile how something can be both a particle and a wave it just defines mathematically that it "behaves as if...". Or do I have a fundamental misunderstanding?

[–]AltoidNerd[S] 1 point2 points  (0 children)


[–]eyeofthephysics 0 points1 point  (1 child)

There is quote by Schwinger I posted somewhere else and to paraphrase it again "In modern physics we are only borrowing names from classical physics". The distinction between a particle and a wave is purely classical. There is no need to reconcile how something can be a particle and a wave at the same time because the distinction is emergent. Don't elevate classical physics and its terms over the actual quantum physics.

[–]AltoidNerd[S] 0 points1 point  (0 children)

Someone should email Jackson about this. He has answered emails from me before.


What were the implications of this paper?

[–]AltoidNerd[S] 2 points3 points  (0 children)

I think it's somewhat contrary to what many people say about spin - it is said that spin is in no way the result of circular currents. This is old, though.


Is it just another nail in the coffin for magnetic monopoles?

[–]Ruiner 2 points3 points  (1 child)

Not really, he's just saying that the dipole moments cannot be explained as a di-poles, that is, one positive and one negative charged monopole bound together. This dipole moment has to be intrinsic. This is not really revolutionary nor it was new at the time, this was a lecture in which he showed how you can understand that using basic electrodynamics.


It was not revolutionary, but he wrote this review for pedagogical reasons, and it's still relevant today. One of my pet peeves is the vehement denial that spin is at all related to rotation, or circular currents, or anything rotating.

I of course do not want to have this debate here. Only wanted to share the 1977 paper where Jackson opines something else - it differs from the norm in the explanation of intrinsic moments today, in that the relationship to circular currents is usually rejected outright.