"How, how can you tell?"
Leonardo watched in amazement as Bi Fang removed the second hand from the watch, rubbed it a few times on his hair, placed it on a leaf, and floated it on water, then pointed to the stationary direction that indicated north and south.
What north and south?
What's that?
[I know, this is Lorenz's theorem!]
[To the one mentioning Lorenz's theorem, I slowly type out a question mark.]
[Isn't this magnetization? Didn't you go to school? It should work on the same principle as a compass, though it's temporary.]
"The principle is actually quite simple, it's the same as how a compass is made, though one is permanent and the other is temporary," Bi Fang explained as he lifted the leaf out of the puddle, drained off the water, and reattached the second hand back onto the watch, securing the dial.