NOVA investigates the unstable future of the Earth's magnetic fields in the episode "Magnetic Storm." Physicist Dan Lathrop leads a team of scientists at the University of Maryland who study this phenomenon. They have made a model of the Earth's iron core using more than 200 pounds of molten sodium. Geologist John Shaw at the University of Liverpool studies the iron minerals in baked clay pots. The minerals provide a historical record of the magnetic field, which has been on the decline for the last few centuries. Scientist Gary Glatzmaier at the University of California believes the Earth is preparing for another swap between the North and South Poles. This episode originally aired on PBS in November 2003.