Sean trips, and his knife falls out of his pocket. He notices that the knife floats in mid-air and checks his compass to find that it isn't working, meaning there is a magnetic field in the area. He travels to the other side of a large opening using large rocks suspended in air, with many close calls during his journey.
The Doctor hides himself in an elementary school to investigate an alien attack. As the teacher, he asks his students various physics questions to understand how much they know. One student, Milo, proves he's unusually smart and triggers the Doctor's interest.
Neil deBuck Weasel and the opossums are happy to find space rocks, which consist of iron, carbon, and a hint of nickel. They soon learn that the rocks have unusually strong magnetic fields and attract to each other. Although largely exaggerated, this clip could be used to illustrate magnetism and the elements found on asteroids.