This type of compass is often used on ships and aircraft.Ī solar compass uses the sun as a navigational tool. Once the gyroscope begins spinning, motion will not disturb it. Since magnetic north is not measured, variation is not an issue. The gyrocompass, invented in the early 20th century, uses a spinning gyroscope to follow Earth’s axis of rotation to point to true north. Some compasses do not use Earth’s magnetism to indicate direction. The most complicated compasses are complex devices on ships or planes that can calculate and adjust for motion, variation, and deviation. Magnetic compasses can have additional features, such as magnifiers for use with maps, a prism or a mirror that allows you to see the landscape as you follow the compass reading, or markings in Braille for the visually impaired. The most basic are portable compasses for use on casual hikes. Deviation must also be taken into account on aircraft using compasses, due to the metal in the construction of an airplane. Adjustments such as placing soft iron balls (called Kelvin spheres) and bar magnets (called Flinders bars) near the compass helped increase the accuracy of the readings. When ships evolved from being made of wood to being made of iron and steel, the magnetism of the ship affected compass readings. Other adaptations have been made to magnetic compasses over time, especially for their use in marine navigation. Navigators must adjust their compass readings to account for variation. Variation is not significant when using magnetic compasses near the Equator, but closer to the North and South Poles, the difference is much greater and can lead someone many kilometers off-course. This discrepancy between magnetic north and true north is called variation (by mariners or pilots) or magnetic declination (by land navigators) and varies depending on location. Eventually, as compasses became more reliable and more explorers understood how to read them, the devices became a critical navigational tool.īy the 15th century, explorers realized the “north” indicated by a compass was not the same as Earth’s true geographic north. In their earliest use, compasses were likely used as backups for when the sun, stars, or other landmarks could not be seen. Western Europeans soon followed at the end of the 12th century. Chinese scientists may have developed navigational compasses as early as the 11th or 12th century. Historians think China may have been the first civilization to develop a magnetic compass that could be used for navigation. All 32 points of direction were eventually added to the compass card. This combination evolved into a fleur-de-lis design, which can still be seen today. A spearhead and the letter T, which stood for the Latin name of the North Wind, Tramontana, signified north. As the needle would settle, the marked end would point toward magnetic north.Īs engineers and scientists learned more about magnetism, the compass needle was mounted and placed in the middle of a card that showed the cardinal directions-north, south, east, and west. Very early compasses were made of a magnetized needle attached to a piece of wood or cork that floated freely in a dish of water. As early as 2,000 years ago, Chinese scientists may have known that rubbing an iron bar (such as a needle) with a naturally occurring magnet, called a lodestone, would temporarily magnetize the needle so that it would point north and south. Scientists and historians don’t know when the principles behind magnetic compasses were discovered. The ends point to what are known as magnetic north and magnetic south. Magnetic compasses consist of a magnetized needle that is allowed to rotate so it lines up with Earth's magnetic field. While the design and construction of this type of compass has changed significantly over the centuries, the concept of how it works has remained the same. They have become so popular that the term “compass” almost always refers a magnetic compass. Magnetic compasses are the most well known type of compass. It is one of the most important instruments for navigation. A compass is a device that indicates direction.
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