Consider a magnet moving towards a coil. We know that the motion of the magnet will induce a current in the coil and the direction of this induced current is to oppose the motion of the magnet. Now does the magnet experience resistance to its motion immediately as soon as it starts moving? Since the magnet and coil are physically separated, it would take a time t (which is equal to the time taken by light to travel from the magnet to the coil) to induce a current in the coil and an equal amount of time for the effect of this current to travel back to the magnet and oppose its motion. Hence the total delay appears to be 2t. So does the magnet experience resistance immediately or does it have to wait for time 2t?