Compass

A compass is a tool that shows the cardinal directions used for finding your way and knowing where you are. It usually has a magnetized needle or something like a compass card that moves to point toward magnetic north. Other tools can also be used, such as magnetometers and GPS receivers.

Compasses often show angles in degrees: north is 0°, and the numbers go up as you move clockwise. So east is at 90°, south at 180°, and west at 270°. These numbers help show directions, called azimuths or bearings, in degrees. If you know the difference between magnetic north and true north, you can use the compass to find the true direction.

The magnetic compass is one of the Four Great Inventions. It was first made a long time ago in China during the Han dynasty (around 206 BC). It was later used for navigation in the Song dynasty. The first records of compasses in Western Europe and the Islamic world are from around 1190.

A magnetic compass points to "magnetic north" because the magnetized needle aligns with the Earth's magnetic field. The needle can turn easily because it is balanced on a point that lets it move freely. When you hold the compass level, the needle will turn until it points in the right direction.

On maps, directions are usually shown using true north, which is the direction toward the Geographical North Pole. The angle between true north and magnetic north can change depending on where you are on Earth. This angle, called magnetic declination, is shown on most maps so you can line up the map with your compass to face true north.

History

Main article: History of the compass

The compass has a long and interesting history. The ancient Greeks found that a special rock called lodestone could pull iron. This rock came from a place named Magnesia in Anatolia.

People in ancient China also learned about lodestone. They made a "south-pointing spoon" to help show directions. Later, they made compasses from iron needles that used lodestone. These compasses helped people find their way when they traveled. Over time, compasses were made better. By the early 20th century, they used liquid-filled needles for more accurate direction finding.

Design

Modern compasses usually have a magnetized needle or dial inside a capsule filled with liquid. This liquid helps the needle move smoothly.

Many compasses also have extra tools, like a protractor, to help with reading maps and taking directions. They might include special sights to look at faraway objects more clearly or scales to measure distances on maps. Some compasses are made for use on boats and have special designs to stay steady even when the boat moves a lot.

Compassesa can be tricky near the Earth's magnetic poles. They can also be affected by nearby metal objects or strong magnetic fields.

Variants

A thumb compass is a special compass used in orienteering, a sport where reading maps and understanding the land is important. These compasses usually do not have many degree markings and are mainly used to line up maps to magnetic north. They often have a large needle to make it easier to see and are sometimes transparent so that a person can look at their map through the compass.

Other compasses include the earth inductor compass, which uses the Earth's magnetic field to find direction. Small electronic compasses, called eCompasses, are found in devices like mobile phones and use tiny sensors to detect direction. There are also special compasses for different purposes, like the Qibla compass used by Muslims to find the direction to Mecca, and the prismatic compass used by surveyors and explorers for very precise measurements. The luopan is a compass used in practices like feng shui.

Construction

To make a compass, you need a magnetic rod. You can make one by rubbing a piece of iron or steel with a special stone called a lodestone. The magnetized rod is placed on a surface where it can move freely. This lets it point toward Earth’s magnetic north, helping people find directions.

Early compasses were simple and showed only north and the four main directions: north, south, east, and west. Later, they were divided into more points. Today, most compasses use a system of 360 degrees around the dial. Some places use different systems, but the main idea is the same: to help people know where they are going.

Use

A magnetic compass helps people find directions by pointing toward magnetic north. This is close to, but not exactly the same as, true north. To get the right direction, you need to adjust for two things: variation and deviation. Variation is the difference between magnetic north and true north. It changes depending on where you are. Deviation happens when nearby metal objects or electric currents affect the compass.

When using a compass with a map, you can find the exact direction to a place by aligning the compass with the map’s north. Some compasses can adjust for the difference between magnetic north and true north. This makes it easier to follow the right path. It’s important to keep compasses away from magnets and electronic devices, as these can mess up the readings. Always place the compass on a flat surface so the needle can move freely.

Non-magnetic compasses

There are several ways to find north without using magnetism. Two special tools that help with this are the gyrocompass and the GPS-compass.

A gyrocompass works like a fast-spinning wheel that uses the Earth's rotation to find the direction of true north. It is often used on ships because it is not affected by certain metals inside the ship. Large ships usually depend on gyrocompasses, while smaller boats might use electronic tools or keep magnetic compasses as a safety backup.

GPS receivers can also find directions very accurately by using signals from satellites in space. These tools can tell not only which way you are going but also how fast you are moving. They are very useful because they find true north and are not disturbed by changes in Earth's magnetic field. However, they need to stay connected to the satellites to work properly.