Thanks for that bcrowell, that was a useful thread.
This is what I came up with:
I bent a uniform linear charge density in a circle such that each charge is experiencing uniform circular motion. Two, actually, a positive one going clockwise, and a negative one going counter clockwise. Thus...
There are plenty of examples where someone derives the magnetic force from a current carrying wire on a moving charged particle by looking at the frame of the particle and finding that the current has Lorentz contracted in such a way as to produce an electric field in an otherwise neutral wire...
This is from from Sakurai and Napolitano HW Prob #2.6. I've done the HW problem and can fit all the pieces together with the mathematical formalism, but even afterwards I'm still scratching my head wondering what I'm looking at.
I start with the commutator [[H,x],x]. If I take...