Re: ORIGINAL simple magnets question

[Leigh Palmer <palmer@SFU.CA>]

> >  1. There is no such thing as an *almost* inertial reference frame.
> >
> >  2. Magnetism is *intrinsically* a relativistic effect. There is
> >     never a justification for ignoring relativity when treating
> >     questions of this sort. Purcell is a good source for teaching
> >     E&M with this fact held constantly in view, as is Feynman.
> >     (These two texts were published within a year of one another.)
>
> I agree with both of these.  If we rotate the entire CERN accelerator,
> locally each magnet assembly will seem to go in a straight line, but still
> there *must* be some GR effects there too.

I'm not worried about GR; that's not my point. I don't even know GR.
My problem is that SR only works in an inertial reference frame, and
the effects of gravity or centrifugal force fields can be measured
directly and accounted for. When one does this one finds that there
are no large effects, for example, due to gravity; SR works well on
Earth's surface. (An example of a situation in which GR becomes
important, in fact more important than SR, is seen in the ticking of
the atomic clocks aboard the satellites of the Global Positioning
System, all of which run *faster* than identical clocks on Earth's
surface when SR alone predicts they should run more slowly.) I doubt
that there are any significant GR effects to be encountered in your
gedanken experiment with the CERN accelerator, but of course no one
will ever do that experiment. That judgment is based solely on
experiments that have already been done.

> By number 2, I meant to avoid using electrons which go at 50% of C,
> because there *might* be additional effects arising when the disk-magnet
> rotates that fast.  Use 1 meter/sec instead, and only deal with the usual
> electromagnetic relativity of moving, everyday-world magnet disks.

Agreed, but one must still do relativistic calculations for 1 m/s
electrons. The entire force which acts on such particles is of a
fundamentally relativistic nature. The source model calculation
will make that quite clear.

Leigh