Facts for Kids

Compass is a small tool that shows directions so people can find their way. Inside a compass there is usually a thin metal pointer or a round card that turns. That pointer lines up with the Earth’s magnetic pull, so you can tell which way is north, south, east, and west.

A compass can also show turns as numbers called degrees. North is 0°, east is 90°, south is 180°, and west is 270°. These numbers are useful when you follow a map or when someone tells you a bearing, which is the angle to walk toward. If you know the tiny difference between magnetic north and true north where you are, you can use a compass to find true north, too.

Lodestone is a special kind of rock that pulls small pieces of iron. Long ago, people found lodestones and saw they could move iron objects without touching them. The word “magnet” may come from Magnesia, a place where such stones were found.

Many old stories and books mention lodestone. A Greek thinker noticed its power around 2,500 years ago, and people in China and India wrote about it, too. In China, one early tool made from lodestone was a small spoon that always pointed the same way. People used these stones for simple experiments, making tools, and even some kinds of medicine in a careful, non-harmful way.

Magnetized needle is the heart of a simple compass. Long ago, people made this by rubbing a small iron or steel rod with a natural magnet called a lodestone. Rubbing the iron in one direction caused its tiny parts to line up, so the needle became a weak magnet and could turn to point north.

Because the old rubbing method made only a weak magnet, compass makers later used stronger magnets or other ways to make needles that keep their strength. Today, needles are carefully balanced on a pin so they turn easily and sit flat, which helps the compass work well.

People learned to make needles act like lodestone by rubbing or striking them with a lodestone so the needle kept a tiny pull. By the late 1000s, Chinese writers described using such needles for finding direction at sea and on land.

Later, around 1300, box-style dry compasses appeared in Europe and the Islamic world. These used a needle that could swing inside a case. In the early 1900s, many compasses began using a clear liquid around the needle. That liquid made the needle settle faster and be easier to read while traveling.

Magnets are only one way to tell direction. Two common non-magnetic tools are the gyrocompass and the GPS-compass. A gyrocompass uses a fast-spinning wheel and Earth’s rotation to point toward true north, so it works well on big metal ships where a magnetic compass might be confused.

A GPS-compass finds direction by using signals from satellites. It often needs to move a little or use two receivers to show heading. Phones and boats use GPS-compasses because they give direction even where magnetic tools are unreliable.

Most modern compasses have a thin magnetized needle or a marked dial inside a small, clear capsule. The capsule is often filled with a liquid that slows the needle’s wobble so it points steadily. The end of the needle that points north is usually painted or has a glowing mark so you can see it at night.

A compass needle lines up with the invisible magnetic field around the Earth, so it points near the planet’s magnetic north. The round dial is marked in degrees, and you turn it until the needle shows the number you need. Many liquid-filled compasses work underwater, because the liquid does not squeeze much under pressure and the needle can still move.

A magnetic compass needle points toward magnetic north, not the exact spot on a map called the geographic North Pole. The difference between those two norths is called variation. Mapmakers and sailors learn the variation for the area and change the compass reading to find true north.

A compass can also be upset by metal nearby or by electric currents. This problem is called deviation, and sailors fix it by adding tiny magnets or making correction tables. With practice—measuring bearings to known landmarks and recording distances—you can plot a course and return using only a compass. For short walks most people don’t need to worry about small differences.