Interesing EM "paradox" This problem has gotten me 3 different answers from 3 different profs. 1. A moving charge produces a magnetic field, and this could be measured by a stationary observer relative to the moving charge. 2. If an observer is moving parallel to the moving charge with the same velocity so that the observer does not see any movement in the charge, does this observer measure a magnetic field? I thought no. And if 2 is correct, then what happens if as the moving charge passes the stationary observer, the observer moving parallel to the charge passes through the same location as the stationary charge. At this instant, the moving charge would be on its closest approach to the stationary observer. I would think the stationary observer would measure a B field, but the moving observer would not measure a B field. But they are in the same location at the same time... What is going on?? This should occur at slow ie non relativistic speeds i think. 3 profs were stumped, are you?