He kept a magnet in his coat pocket. How it attracted nails and other bits of metal was an endless source of fascination, and the way it spun the needle of his compass, round and round the world. What magic was inside that horseshoe-shaped bit of iron? Whatever it was, Lenny never tired of playing with his favorite toy.
What he didn’t know was that the whole Earth is a magnet. Or that the earth-magnet was a providential force, that protected him from deadly solar radiation, bending the paths of charged particles into safe orbits. For the moment such things were beyond Lenny’s imagination.
“Tell me about magnets, George.”
A field is nothing but a function of space and time that usually represents ...