Compass

A compass is a tool that shows which direction is north. It uses a small magnet, usually a thin needle, that can spin freely. Earth itself acts like a giant magnet, and the needle lines up with Earth's magnetic field. Once you know which way is north, you can also figure out south, east, and west.

The first compasses were invented in China more than 2,000 years ago. Early Chinese compasses were not used for travel at first. They were used for fortune-telling and for lining up buildings with the directions. By about the year 1000, Chinese sailors were using compasses to find their way at sea. The idea slowly spread west to the Arab world and then to Europe.

A simple compass has just a few parts. There is a magnetized needle, a pivot point so the needle can spin, and a flat card marked with the directions. The needle has two ends. One end is painted red or marked in some way, and that end always points north. To use a compass, you hold it flat and wait for the needle to stop moving. Then you turn yourself, or your map, until the markings line up.

Before the compass, sailors had to steer by the sun during the day and the stars at night. That worked fine in clear weather. In fog or storms, sailors could get lost for days. The compass changed everything. Ships could now sail far from land in any weather. This new tool helped power the Age of Exploration in the 1400s and 1500s, when explorers like Columbus and Magellan sailed across the oceans.

The needle does not point to the true North Pole, the spot at the very top of the globe. It points to a different spot called the magnetic north pole. The magnetic pole is hundreds of miles away from the true pole, and it moves a little each year. Scientists are not sure exactly why it moves, but they think it has to do with hot, swirling iron deep inside Earth.

Today, most phones have a digital compass built in. It works in a similar way, using tiny sensors that can feel Earth's magnetic field. Hikers, sailors, and pilots still carry old-fashioned magnetic compasses too. A real compass needs no battery and no signal. As long as Earth keeps its magnetic field, it will keep working.