Intuitive physics

[snousle]

Here's a thought experiment that touches on a lot of different intuitions and assumptions. I'm curious to see how people answer:

You have two hockey-puck shaped permanent magnets, and you place one on each side of a thin sheet of plastic such that their mutual attraction clamps them strongly together. All surfaces are smooth and nearly frictionless (oil them if you like). If you hold the sheet stationary while rotating one of the magnets, does the other one rotate as well? Why or why not?

Comments

[come-to-think.livejournal.com]

This argument is an abuse of the notion of lines of force. The two magnets do not have independent fields that reach out & tangle with each other. There is only one magnetic field, and its lines go from the S pole of one magnet to the N pole of the other (thru the sheet), and then from the S pole of that magnet back to the N pole of the first one (thru the surrounding space). These lines are imaginary constructs of arbitrary density (like the lines of latitude & longitude on the earth). They show the direction of the field at any point on them, and if you pick out a bunch of neighboring ones, their density will represent the strength of the field; but they are not threads.