Mr. Magnetic

I walked into the kitchen one morning this summer and found James preparing to dash his wooden trains through the air and against the wall. He was frustrated that he could not push them together. I showed him the round magnets at each end of the engine and train cars and told him were two round, different magnetic poles on each train, one positive and one negative. I demonstrated that trying to connect two positives or two negatives would push the cars apart.

"So," I explained, "if they won't go together, turn one car around to the other magnet, and they'll both snap together."

This is what happened for the next 15 minutes:

and:

and:

Why couldn't my sciences classes have been more like this?