Re: simple magnets question

[John Denker <jsd@MONMOUTH.COM>]

At 04:28 PM 6/24/99 -0400, Michael Edmiston wrote:
> ... his question has switched from being a "simple" magnet question
> to being a complicated magnet question.  I think the underlying
> question is a question of relativity... and relativistic
> electrodynamics is not simple.

I disagree.

Consider the analogy:  rocket science is proverbially complex.  But the
essential physical principle of rocketry is just Newton's law of action and
reaction.

In the same way, relativistic electrodynamics can be quite complicated if
you want to apply it to complicated situations.  But we haven't got a
complicated situation here.  The essential physical principle is that if
you've got a magnetic field in one frame, you've got electric *and*
magnetic fields in another frame.

Specifically, assume Moe observes a magnetic field in the Z direction.  Joe
is moving relative to Moe with modest velocity V in the X direction.  Then
Joe observes an electric field, which to first order in V/c is:

        Ey(Joe) = Vx Bz(Moe)

which is about as conceptually and quantitatively simple as anything could
possibly be.

Given enough smoke and mirrors one could try to dress this up as something
complicated, but there's not much to be gained thereby.