Which fundamental force makes a compass needle point north?

A compass needle points north because it is a tiny magnet interacting with Earth’s magnetic field. Magnetism is one aspect of the electromagnetic force, one of the four fundamental interactions. Earth’s magnetic field is generated by moving electric charges in the planet’s liquid outer core, a process called the geodynamo. The modern understanding of electricity and magnetism was unified in the 19th century by James Clerk Maxwell’s equations. That same force underlies light, chemistry, and all ordinary matter interactions.