As I was cleaning up this morning -- putting things away for winter -- I discovered something unusual that I can't explain using any Physics I know...
I have a steel router table. On it I have a magnetic feather-board -- a strong, ceramic magnet in a holder that then has 'fins' on it to keep the work being routed tight to the fence. The table, despite it being cold and damp was rust free -- EXCEPT under where the magnet was! As I lifted off the feather-board, I found a perfect rust outline of the magnet inside the feather-board!
Now, why would that be? If all the other surfaces are rust-free, what would cause the magnet to induce rust? (I'm always looking for practical examples of physics to show/describe to my students.)