Need Direction in Life? USE A COMPASS!


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By Ann

Have you ever gotten lost and lost all sense of direction? Imagine losing your sense of direction in the middle of the ocean! Compasses are vital to navigation while sailing so sailors can have an understanding of their location and have the ability to navigate where they are heading.

History:

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Compasses were first constructed in ancient China and were first documented in 70 A.D. Originally, the Chinese people did not use compasses as a source of navigation, but rather to construct buildings in accordance to the principles of Feng Shui. The first time that the Chinese have documented use for the compass for navigational purposes is year 1119 A.D.

In Europe, the first documented use of a navigation compass was in 1187 A.D. when Alexander Neckam used the magnetic compass as a source of direction on the English Channel. However, it took time before the compass was commonly used for navigational purposes in Europe. Eventually, in 1410 A.D., the magnetic compass was commonly used by sailers traveling the the Bay of Biscay, a fundamental trading route in Europe.

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The compass is also mentioned in Islamic writings as a source to find Mecca.

How Compasses Work:

Both the North and South Poles are magnetic which enable compasses to function. The compass has a magnetic needle with one end that is attracted to the North Pole. The needle in the compass rotates on a pivot point with close to no friction, allowing it to spin easily.

The Magnetic North (the magnetic pole of the earth) is different from True North (what is considered North on a map) because the Magnetic North is constantly changing. Becuase Magnetic North is always moving, it leads to a margin of error called declination in which there is an angle of difference between Magnetic North and True North.

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Application:

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When sailing, compasses are necessities in order to travel to the desired location. To find more information about how the magneticism of compasses are used while sailing, I interviewed my dad who went on a sailing trip for six months to the Bahamas thirty five years ago. My dad explained that compasses are important when sailing becuase they are used to plot the boat's location. He told me a story about when his boat was drifing due to the winds from a hurricane and his boat drifted to the coast of Cuba. Outside Cuba's coast, there was a ship reck that was plotted on the map they were using. To find their location, he used a compass to find the angles of the boat from the reckage. He then explained that he used this parallel line device in order to accurately draw these angles on the map, and the point where the lines intersected on the map was the location of the boat.

He also described using a compass while traveling through different currents. For example, once he was traveling off of the coast of Florida, and there was a current of 2.5 mph due North, and a current of 5 mph 45 degrees due South of East. He used triganometry to find how long the sail boat should travel, in which direction to arrive at their desired location. He used triganometry and solved for the angle of sine of .5 to get an angle of 30 degrees.



One of the problems that my dad described while sailing was the fact that at times the compass was not always accurate. For example, sometimes the compass would not point directly to True North, but would instead point to the Magnetic North. This would leave the compass pointing a few degrees in the wrong dirction leaving him with some inaccurate calcluations.

Works Cited:

http://en.wikipedia.org/wiki/Compass

http://adventure.howstuffworks.com/outdoor-activities/hiking/compass-or-gps2.htm