How does a compass work?
A compass works because its magnetized needle lines up with Earth's magnetic field. One end of the needle points toward the magnetic north pole, which is near the geographic North Pole.
Earth behaves like a giant magnet because of molten iron moving in its outer core, which creates a magnetic field. A compass needle is a small, lightweight magnet balanced on a pivot so it can turn freely. Its north-seeking end swings to point along the magnetic field lines, toward magnetic north.
Magnetic north and true north are not exactly in the same place. The difference, called magnetic declination, depends on where you are on Earth and changes over time. Map readers and navigators adjust for it. The magnetic north pole itself moves, drifting several tens of kilometers per year in recent decades.
History of the compass
The first compasses were developed in China, where lodestone, a naturally magnetic rock, was used for direction finding. By the 11th century, Chinese sailors were using magnetic needles for navigation. The compass reached Europe around the 12th century and transformed sea travel during the Age of Exploration.
Did You Know?
Keep a compass away from phones, speakers and metal objects, which can disturb the needle and give a false reading.