“To convey the operation of electromagnetic fields, Feynman used the master metaphor of two corks floating in a pool of water. If you move one cork around in the water, you immediately notice that the other one moves, too. Looking only at the two corks, Feynman explained, a naive physicist might be forgiven for thinking there was some kind of interaction between the corks that caused one to move in response to the other.

The second cork, however, is not moved directly by the first cork but by the movement of the water. "If we jiggle the cork...waves travel away," Feynman explained, "so that by jiggling, there is an influence very much farther out, an oscillatory influence. That cannot be understood by the direct interaction. Therefore the idea of direct interaction must be replaced with the existence of the water, or in the electrical case, with what we call the electromagnetic field.”