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38 经度线的探索及其对安全航海的作用

DATE=6-20-01

TITLE=EXPLORATIONS #1957 - Longitude

BYLINE=Oliver Chanler

VOICE ONE:

This is Steve Ember.

VOICE TWO:

And this is Bob Doughty with the VOA Special English program EXPLORATIONS. Today, we tell about how people learned an important piece of information necessary for safely sailing on the oceans. It is called longitude.

(((THEME)))

VOICE ONE:

On a foggy October night in Seventeen-Oh-Seven, four English (1) navy ships hit rocks in the Atlantic Ocean and sank. Two-thousand men (2) drowned. The ships had been sailing in the thick fog for twelve days. There was no sure way to know where they were. The commander of the ships had been worried that they could hit rocks if they were not careful. He asked his (3) navigators for their opinion on their location in the ocean

. The navigators did not really know. They told the commander they thought they were west of a small island near the coast of northwestern France

. They were wrong. Instead, they sailed onto rocks near a small group of islands southwest of England's Atlantic coast. The navigators' lack of knowledge led to the loss of four ships and two-thousand lives.

VOICE TWO:

When people began sailing out of sight of land, sailors did not know how to tell where they were on the open sea. Land travelers can look at a mountain, a river, or an object that shows them where they are in relation to where they came from. On the ocean, however, there is no sign to tell a sailor where he is

. The most important device for knowing directions on the ocean is a (4) compass. A compass is a (5) device containing a metal object that points toward the

(6) magnetic north pole. This shows navigators the direction of north, and therefore also south, east, and west. But sailors need more information to sail safely on the open sea.

VOICE ONE:

Most maps of the world show lines that are not on the Earth's surface. One line is the equator. It is an (7) imaginary line around the widest part of the Earth. There are similar lines both north and south of the (8) equator. These circles become smaller and smaller toward the north pole and the south pole.

These lines, or circles, are (9) parallel - meaning that they are equally distant from each other at any point around the world. These lines show what is called (10) latitude.

A navigator can know the latitude of his ship by observing the location of stars, where the sun rises in the morning and sets in the evening, and what time of year it is. With this information he knows where his ship is in relation to the north or south pole and the equator.

VOICE TWO:

Still, there is one more important piece of information necessary for safely sailing the oceans. For many centuries, scientists, (11) astronomers and inventors searched for a way to tell longitude. The lines of (12) longitude go the other way from latitude lines. They stretch from the north pole to the south pole, and back again in great circles of the same size. All of the lines of longitude meet at the top

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