I was given this problem to think about from my professor. It's not for any class. It went something like this: Imagine there is some magnetic field in empty space (tightly-packed lines curling around in a circle) at t=0. What happens to the field as t -> infinity. I figured Maxwell's equations might help, but they all talk about a current being involved. From what he said, though, it seems like the field lines are just there, in empty space. How did they get there, though, and what would sustain them? Thanks.