Above a certain heat level, magnetic materials lose their ability to stick to other magnets. You hang a small rare-earth magnet on a wire pendulum next to a large ceramic magnet — the rare-earth magnet jumps up and sticks. A candle flame sits right beneath that contact point. When the flame heats the small magnet past its Curie point, gravity pulls it away from the big magnet and out of the flame. It cools, regains its magnetism, and snaps back up. The cycle repeats as long as the candle burns.