Compass

A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It typically consists of a magnetized needle or another element, such as a compass card or compass rose, that pivots to align itself with magnetic north. Other methods may be used, including gyroscopes, magnetometers, and GPS receivers.

Compasses often show angles in degrees: north corresponds to 0°, and the angles increase clockwise, so east is 90°, south is 180°, and west is 270°. These numbers allow the compass to show azimuths or bearings which are commonly stated in degrees. If local variation between magnetic north and true north is known, then direction of magnetic north also gives direction of true north.

Among the Four Great Inventions, the magnetic compass was first invented as a device for divination as early as the Chinese Han dynasty (since c. 206 BC), and later adopted for navigation by the Song dynasty Chinese during the 11th century. The first usage of a compass recorded in Western Europe and the Islamic world occurred around 1190. The magnetic compass helps people find their way by pointing toward Earth's magnetic north, making it an essential tool for travelers, explorers, and anyone needing to navigate through unknown places.

History

Main article: History of the compass

The compass has a long and interesting history. One of the earliest known references to magnetism was made by the Greek philosopher Thales of Miletus around the 6th century BC. He noticed that a natural stone called lodestone could attract iron.

Later, in ancient China, people used lodestone to create devices that could point north. By the year 1088, Chinese inventors made compasses using iron needles that were magnetized with lodestone. These compasses helped people navigate during their travels. Eventually, compasses made their way to Medieval Europe and the Islamic world, where they became very important tools for sailors and explorers.

Design

Modern compasses usually have a magnetized needle or dial inside a liquid-filled capsule. This liquid helps the needle move smoothly and stay steady. Special materials on the compass let you see it even in the dark. Many compasses also have tools for measuring angles and directions on maps.

Some compasses, like those used by the military, have a card instead of a needle and special sights for aiming. These compasses can be used in many places around the world. However, compasses can be affected by magnetic fields from metal objects or electronic devices, which can make them less accurate.

Variants

A thumb compass is often used in orienteering, a sport that involves reading maps and understanding the terrain. These compasses usually have very few degree markings and are mainly used to align maps to magnetic north. They often have a large needle or indicator to make it easier to see and may be transparent so you can look at a map through the compass.

Other types of compasses include the earth inductor compass, which uses principles of electromagnetic induction and the Earth's magnetic field. Small electronic compasses, known as eCompasses, are found in mobile phones and other devices. These use tiny sensors to detect the Earth's magnetic field and help determine direction.

Specialty compasses include the Qibla compass used by Muslims to find the direction to Mecca, the prismatic compass used by surveyors and explorers for very accurate readings, the trough compass used for land surveying in the past, and the luopan used in feng shui practices.

Construction

To make a compass, you need a magnetized rod. One way to magnetize a rod is by rubbing it with a natural magnet called a lodestone. This rod is then placed so it can pivot freely, allowing it to point toward magnetic north. Early compasses were simple, using a magnetized needle floating in water.

Over time, compasses evolved to include a dial marked with directions. Today, most compasses use a 360-degree system, where the circle around the compass is divided into 360 equal parts. Some places use different systems, like dividing the circle into 400 parts called grads. Compasses need to be balanced so they work properly in different parts of the world. They can be affected by metal and electricity, so they should be used away from cars, trucks, and other metal objects.

Use

A magnetic compass points toward magnetic north, which is not exactly the same as the true geographic North Pole. By understanding this difference and making small corrections, people can use a compass to find their way accurately.

When using a compass with a map, you can align the compass with the map to get a direction to a destination. It’s important to keep the compass on a flat surface and away from magnets or electronic devices, as these can interfere with its readings.

Non-magnetic compasses

Besides magnetic compasses, there are other ways to find north for navigation. Two important types are the gyrocompass and GPS compass.

A gyrocompass uses a fast-spinning wheel to find true north, the direction of Earth’s rotation, and is not affected by metal on ships. Large ships often use gyrocompasses, while smaller boats may use electronic compasses or still rely on traditional magnetic compasses.

GPS receivers can also determine direction very accurately by knowing their position on Earth. They find true north and are not disturbed by magnetic fields, though they need to communicate with satellites in space to work.