Earth behaves like a giant magnet with magnetic poles near its geographic poles.

The longer version

Deep inside Earth, molten metal churns as the planet rotates, and that moving conductor generates a magnetic field. The field stretches far out into space and loops back on itself, much as it would around an ordinary bar magnet tilted slightly relative to the spin axis.

Because the flow is turbulent, the magnetic poles wander slowly and occasionally swap places over long spans of time. Compasses point along the local field rather than at true north, and the gap between the two is called declination. The field also deflects charged particles streaming from the Sun, and without that shielding the surface would receive far more radiation.

Where this entry sits

Everyday physics and chemistry hide small wonders in plain sight, from kitchen reactions to the light in the sky. These short facts explain matter, energy, electricity, magnets, sound, and the simple units we use to measure the world. The full list sits on the Science and Physics page, where every entry is listed in order.