Following up my last reply...
Stephen A. Lawrence wrote: > Consider a pure B field (no E field) in inertial frame S. Consider two > identical particles, particle P1, at rest in S, and particle P2, moving > in S. P1 feels no force, and is not accelerating. A devout relativist (which I am not) would say there is no magnetic field for observer in P1's frame because that frame is at rest w.r.t. to a given charge distribution. > P2 feels a force, > and _is_ accelerating. The (Boolean-valued) existence of an > acceleration is absolute (at least as long as we stick with inertial > frames) -- a particle which is accelerating, is accelerating in all > frames; a particle which is "inertial" is inertial in all frames. Likewise, a devout relativist would say the relative motion of P2 w.r.t. to a given charge distribution generates a magnetic field. > So, > in all inertial frames, P1 will feel no net force, while P2 will feel a > net force. Since the only difference between the particles is their > velocity, yet they feel difference forces, they are clearly subject to a > velocity-dependent force. The E field isn't velocity dependent, so it > can't account for the difference. Ergo, there's a B field in every frame. For a devout relativist there is no a-priori magnetic field in every frame. Harry
