Retarded propagation of magnetic field leads to contradiction

From: Eugene (eugenev_at_synopsys.com)
Date: 07/30/04 

Date: Thu, 29 Jul 2004 23:49:13 -0700

Consider simple experiment:

A magnet and a wire loop are separated by the distance R.
If both of them are at rest, there is no current in the loop.

If the magnet starts to move then (we assume that the
magnetic field propagates with the speed of light) the current
starts to flow in the loop only after time R/c

If the magnet stands still, but the loop moves and
crosses the magnetic lines, the current starts to flow
immediately.

As from the relativity principle both these situations should
be equivalent, we got a contradiction.

SOLUTION OF THIS PARADOX: Magnetic field propagates
instantaneously.

This solution cannot be rejected by invoking the causality
paradox (i.e., apply the Lorentz transformations and show that
there is a moving frame of reference in which current starts to
flow BEFORE the magnet moves) This is because the
Lorentz transformations are not exactly applicable to this system:
One should take into account their dependence on interaction.
Then, the shift of the magnet and the onset of the current become
simultaneous in ALL reference frames.

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