Electromagnetic force permeates our planet. In essence, Earth itself acts like a giant spherical magnet. This is caused primarily by the motion of electrical currents within Earth, probably through the liquid metallic part of Earth’s core. Combined with Earth’s rotation, the core acts like an electric dynamo, or generator, creating a magnetic field.

Earth’s magnetic field extends thousands of miles outward into space. Magnetic field lines, carrying and projecting electromagnetic force, anchor at Earth’s magnetic poles (north and south) and bulge outward, usually in large loops. Occasionally, they stream outward into space. The magnetic north and magnetic south poles of Earth’s magnetic field are very close to the geographical north and south poles, which mark the axis of Earth’s rotation. (Be careful, by the way. There are two ways to define Earth’s magnetic poles—the “magnetic north pole” is on an island in Canada, but the “geomagnetic north pole” is actually on Greenland, and the “geographic north pole” is on an ice shelf floating on the ocean, hundreds of miles from any land.)