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article 2 Eng full.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<title>Navigational Devices (Enf)</title>
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<center><h1>Navigational Devices</h1></center>
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From the earliest of times, sailors have found ways to
<a class="hideDisplay"><font color="blue"><ins><strong>navigate</strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover"> navigate (verb) [ˋnævə͵get ]<br/><br/>
(to direct the way that a ship, aircraft, etc. will travel, or to find a direction) <br/><br/>
<em>Sailors have special equipment to help them navigate.</em></span></span></a>
their ships on the seas and oceans of the world. The earliest sailors navigated by simply following the coastline. Aside from being a rather slow method
of navigating, this method was also rather dangerous and limited. It was dangerous in that waters close to the shoreline could be shallow enough to strand
a ship or the waters could be full of rocky <a class="hideDisplay"><font color="blue"><ins><strong>protrusions</strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">protrusion (noun) [proˋtruʒən]<br/><br/>
(something that sticks out from a surface)<br/><br/><em>The dinosaur has a series of protrusions along its back.</em></span></span></a>
capable of sending ships to their graves. When seafarers began sailing out of sight of land more than 4,000 years ago, they used the stars to determine
their direction. They calculated the distance traveled from their speed and sailing time, and they drew rough charts and maps to find their way and to
exchange information about navigational routes with others. It had also been known as early as 300 B.C. that a <a class="hideDisplay">
<font color="blue"><ins><strong>sundial</strong></ins></font><span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">
sundial (noun) [ˋsʌn͵daɪəl] <br/><br/>
(a device to show the time of day by the position of the shadow cast on a marked plate)<br/><br/>
<em>People used sundials to tell times in ancient times.</em></span></span></a>
casts a longer shadow as it is moved farther north of the equator
, and this information was used by sailors from that time to get an idea of how far north
of the <a class="hideDisplay"><font color="blue"><ins><strong>equator </strong></ins></font><span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">equator (noun) [ɪˋkwetɚ]<br/><br/>
(an imaginary line drawn around the middle of the earth)<br/><br/><em>Indonesia is on the equator.</em></span></span></a>
a ship was. All of these methods provided only very <a class="hideDisplay"><font color="blue"><ins><strong>rudimentary </strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">rudimentary (adj) [͵rudəˋmɛntəri] <br/><br/>
(basic)<br/><br/>
<em>He has only rudimentary knowledge of math.</em></span></span></a>
means of navigating.
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It was not until more than 3,000 years after sailors set out on
the seas that the compass was developed. The <a class="hideDisplay"><font color="blue"><ins><strong>premise </strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">premise (noun ) [ˋprɛmɪs]<br/><br/>
(an idea or theory on which a statement or action is based)<br/><br/><em>
The research project is based on the premise stated earlier.</em></span></span></a>
of a compass is that the<a class="hideDisplay"><font color="blue"><ins><strong> magnetized </strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">magnetize (verb) [ˋmægnə͵taɪz]<br/><br/>
(to make something that is able both to attract iron and steel objects and also push them away)<br/><br/><em>
Each worker has to carry a magnetized plastic entry card.</em></span></span></a>
needle of a compass, when<strong> <u>it</u></strong> is balanced on a central<a class="hideDisplay"><font color="blue"><ins><strong> pivot </strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">pivot (noun) [ˋpɪvət]<br/><br/>
(a fixed point supporting something that turns or balances)<br/><br/><em>
There is a pivot point at the center of a seesaw.</em></span></span></a>
or left to float on liquid, will always turn to point in the direction of magnetic north. Navigators on Chinese ships were the first
ones who were known to use compasses to determine the direction their ships were heading, as early as 1100.
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Numerous inventions were created to determine a ship's
<a class="hideDisplay"><font color="blue"><ins><strong>latitude</strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">latitude (noun) [ˋlætə͵tjud]<br/><br/>
(the latitude of a place is its distance from the equator)<br/><br/><em>
Toronto shares the same latitude as Nice. </em></span></span></a>.
With the invention of the <a class="hideDisplay"><font color="blue"><ins><strong>astrolabe</strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">astrolabe (noun) [ˋæstrə͵leb]<br/><br/>
(a circular device used for measuring the position of stars, and on ships for calculating the ship's position)<br/><br/><em>
People used astrolabe to identify stars or planets in the 14th century.</em></span></span></a>.
in the fourteenth century, sailors were able to measure the Sun's height with better accuracy than with a sundial, and they were
able to use the information provided by the astrolabe to determine how far north of the equator they were. An astrolabe was a
metal circle with a sighting rule that<a class="hideDisplay"><font color="blue"><ins><strong> rotated</strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">rotate (verb) [ˋrotet]<br/><br/>
(to turn or cause something to turn in a circle)<br/><br/><em>
The wheel continued to rotate.</em></span></span></a>
in the circle; the <u><strong>rule</strong></u> could be<a class="hideDisplay"><font color="blue"><ins><strong> aligned </strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">align (verb) [əˋlaɪn]<br/><br/>
(to put two or more things into a straight line)<br/><br/><em>
Align the ruler with the edge of the paper.</em></span></span></a>
with the Sun, and measurements on the ring indicated the Sun's height. Other devices followed that were better able to determine the Sun's height
and thus provide an idea of the ship's latitude. The backstaff, invented in 1595, and the
<a class="hideDisplay"><font color="blue"><ins><strong> sextant </strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">sextant (noun) [ˋsɛkstənt]<br/><br/>
(a device used on a ship or aircraft for measuring angles)<br/><br/><em>
There are many sextants in the space museum.</em></span></span></a>
, invented in 1757, were devices that each improved a navigator's ability to determine latitude. The backstaff was a device that required the navigator
to face away from the Sun and make a calculation of the shadow in relation to the horizon. The sextant was a measuring device that required the navigator
to look into an eyepiece and calculate the Sun's position relative to the horizon and then check printed tables to convert this information into latitude.
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<strong>The missing piece in the navigational puzzle </strong>was the ability
to calculate<a class="hideDisplay"><font color="blue"><ins><strong> longitude</strong></ins></font>
<span class="showDisplayOnHover"><span class="showBodyOfDisplayOnHover">longitude (noun) [ˋlɑndʒəˋtjud]<br/><br/>
(the distance of a place east or west of an imaginary line between the North Pole and the South Pole, measured in degrees)<br/><br/><em>
The line of zero degree longitude passes through Greenwich.</em></span></span></a>
, or how far east or west a ship had traveled. The need for a device to calculate longitude was so important to navigators that the
English Parliament offered a reward of 20,000 pounds (an extraordinarily large sum at the time, perhaps $10 million in today's currency)
to anyone who could invent a method for calculating longitude. In 1759, English clockmaker John Harrison built a chronometer that was
accurate enough for navigation. <strong>The premise of the device was that the Sun rises two seconds later each day for each kilometer traveled
in a westerly direction, so the accurately measured change in time was an accurate way to calculate longitude.</strong> Harrison was easily
able to convince Parliament that the reward was warranted.
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