Re: simplier is more difficult

["James W. Wheeler" <jwheeler@eagle.lhup.edu>]

I didn't think that a uniform magnetic field was possible (except as an
approximation).  
Three thoughts (not-coherent)
1.  The assymetry is that electric charges exist, and magnetic monopoles
     do not. (Cabrerra notwithstanding) This means that all
     real electric and magnetic fields are the superposition of
     relativistically transformed electric fields. (N.B. the superposition
     of transformed fields need not be the transform of a single field.)
2.  What about the intrinsic magnetic moments of elementary particles.
     These are relativistic in origin, but need not represent moving
     charge.
3.  Since charge cannot be created, perhaps we should believe that
     current rather than charge is intrinsic.  Maybe all electric fields
     are transforms of magnetic fields!  Isn't duality fun! Pick your
     basis.

On Wed, 8 Oct 1997, David Bowman wrote:

> Ludwik wrote:
>
> > Yes, I do know that magnetism can be presented without introducing the 
> > N-word.
>
> The N-word that Tom was referring to was 'nuclear' not 'north'.
>
> >         And that the concept of magnetic field can also be eliminated 
> > beacuse B can be viewed a relativistic manifestation of E.  ....
>
> This is not true in general.  The only magnetic fields which can be so
> eliminated are those which result from applying a Lorentz tranformation to
> the purely electric field of a charge distribution that is static is *some*
> inertial frame.  Take the simplest case of a uniform pure B field.  There is
> *no* frame for which it completely vanishes.  If one is to treat a particle's
> (or many particles all with the exact same charge to mass ratio) behavior
> when it (they) finds itself (themselves) in a uniform B field then the effect
> of that B field on the system can be eliminated *to first order* (in B) by
> considering the system in an appropriate uniformly rotating coordinate system
> whose axis of rotation is parallel to the B field and whose rotation rate is
> proportional to the B field strength.  But even here there is an induced 2nd
> order effect through the centrifugal effect in the rotating coordinate system
> which doesn't cancel out even though the first order (in B) Lorentz force is
> canceled by the Coriolis effect.
>
> David Bowman
> dbowman@gtc.georgetown.ky.us