Modern compasses usually use a magnetized needle inside a capsule completely filled with a liquid, such as mineral oil or alcohol.s

THE COMPASS

Good morning, in this brief presentation, I’d like to talk about a very important invention of all time, the compass. A compass is an instrument used for navigation and orientation that uses a magnetized needle to show direction relative to the geographic "cardinal points", indicating the magnetic north instead of the true north. Usually, a diagram called a compass rose (wind rose), shows the directions north, south, east, and west as abbreviated initials marked on the compass and angle markings in degrees are shown on the compass: north corresponds to zero degrees, and the angles increase clockwise, so east is 90 degrees, south is 180, and west is 270.

History

The compass was first invented in China as a device for divination by the Chinese Han Dynasty and later adopted for navigation by the Chinese Song Dynasty during the 11th century. First compasses were made of lodestone, a naturally magnetized piece of the mineral magnetite. Later compasses were made of iron needles, magnetized by striking them with a lodestone. Dry compasses appeared for the first time around 1300 in Medieval Europe. In the early 20th century, this was supplanted by the liquid-filled magnetic compass.

“Model of a Han Dynasty. It is theorized that the south-pointing spoons of the Han dynasty were magnetized lodestones. “ (foto)

“Dry compass: It consists of three elements: A magnetized needle in a little box with a glass cover and a wind rose. It always indicates the course of the ship.” (foto)

Modern compasses

Modern compasses usually use a magnetized needle inside a capsule completely filled with a liquid, such as mineral oil or alcohol.

• Thumb compass: type of compass commonly used in orienteering, a sport based in map reading. Most thumb compasses have minimal or no degree markings at all and are also often transparent so that an orienteer can hold a map in the hand with the compass and see the map through the compass.
• Gyrocompass: is similar to a gyroscope. It is a non-magnetic compass that finds true north by using an (electrically powered) fast-spinning wheel. Another main advantage is gyrocompasses are not affected by perturbations of the Earth's magnetic field. Gyrocompasses are mostly used on ships. Large ships typically rely on a gyrocompass, using the magnetic compass only as a backup.
• Solid state compasses: some examples are small compasses found in clocks, mobile phones, and other electronic devices. The device outputs a digital signal proportional to its orientation. This signal is interpreted by a microprocessor.
• GPS receivers used as compasses: Small, portable GPS receivers determinate positions (latitudes and longitudes) and also directions. By determining its position on the Earth a few seconds apart, the device can calculate its speed. GPS compasses share the main advantages of gyrocompasses. Compared with gyrocompasses, they are much cheaper and they work better in polar regions. However, they depend on the functioning of the GPS satellites, which might be interrupted by an electronic attack or by the effects of a serious solar storm.

How to use a magnetic compass

In orienteering:

1. First of all, we have to put the longest side of the compass on the map, between the zone of exit and the zone of arrival, with the direction arrows of the motherboard pointing to the direction of the march.
2. Secondly, we have to turn the capsule of the compass without detaching it of the map, until the lines of North - South are parallel with the lines of the meridians North - South reflected in the map. The North will be marked by an arrow in the compass.
3. Finally, the direction we must take to reach our destination is the one that the direction arrows of the motherboard indicate to you.

Conclusion

To sum up, it’s clear to me that the compass is one of the most important inventions in history. Owing to the invention of the compass, man is able to determine his position and his direction, two things of particular relevance in order to locate yourself. People can orientate themselves anywhere they want to go and discover new routes and places thanks to the use of the compass.

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