Here's why:

* Earth is a giant magnet: Our planet has a magnetic field that extends from its core outward into space.

* Magnetic poles: This field has a north and south magnetic pole, which are not exactly aligned with the geographic poles.

* Attraction and repulsion: A magnet has its own north and south poles. Like poles (north-north, south-south) repel each other, while unlike poles (north-south) attract each other.

* Alignment: When a magnet is free to move, its north pole will align with the Earth's magnetic south pole, and its south pole will align with the Earth's magnetic north pole.

This is why compasses, which are basically small magnets, point north.