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【听力文摘】北极星为何如此特别?

2014-07-29    来源:普特英语听力    【      美国外教 在线口语培训
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What Makes The North Star So Special?

Even if you’re not an astronomy buff, chances are you can easily recognize certain constellations and stars such as the Big Dipper, Orion’s Belt and the North Star.

A Special Star
The North Star is the brightest star in the constellation known as the Little Dipper. It is so-called because of the special position it occupies relative to Earth’s axis. If you were to stay up all night gazing at the stars, you’d slowly see them revolve around a point in the sky known as the North Celestial Pole.

You would notice, however, that one star remains stationary. This is the North Star, so named for its location almost directly in line with the North Celestial Pole.

Early GPS?
Due to its consistent position in the sky, at one time sailors used the North Star as a navigational tool. By measuring the angle between the northern horizon and the North Star, a navigator could accurately determine the ship’s latitude.


But latitude, or the imaginary lines stretching across the globe parallel to the equator, was not enough to pinpoint a ship’s location. Knowing latitude only allowed navigators to locate themselves on a particular latitude line at a particular distance from the equator. It was only with the invention of a way to accurately measure longitude that precise navigation became possible.

Although the North Star is no longer used by navigators, it remains a heavenly icon of human curiosity and exploration.

北极星何“奇”之有?

即使你不是一名天文学发烧友,你也能轻易地辨认出某些星座,比如,北斗七星,猎户座的腰带,还有北极星。

这颗星星很特别

北极星是小熊座中最明亮的一颗星.它的名字源于它所处的特殊位置,这个位置与地轴有关。如果你熬夜盯着满天繁星看,会慢慢发现它们都绕着天上的一个点旋转,这个点就是北天极。

这时,你会注意到有一颗星星一动不动,它就是北极星。北极星因自身位置几乎与北天极重合而得名。

早期全球定位系统?
由于北极星在天上的位置永远不变,所以曾经一度,水手们将北极星作为导航工具。通过测量北方地平线与北极星之间的角度,导航员能确定船只所处的纬度。

但纬度,或者,想象中与赤道平行环绕地球的那条线,不足以确定船只的位置。知道纬度,导航员也只能确定自己在哪条纬线上,距赤道有多远。只有发明出测量经度的方法,进行准确的导航才会成为可能。

尽管如今导航员已不靠北极星来导航。但它代表着人类永恒的探索与开创精神,将永远在天空中绽放光芒。

 【本译文由普特网友 veroniquelj 提供】

PS:因为地球是围绕着地轴进行自转的,而北极星正处在地轴的北部延长线上,所以夜晚看天空北极星是不动的,而且在头顶偏北方向,所以才可以指示北方。虽然在一年四季里,由于地球绕太阳公转,地轴倾斜的方向也发生变化,但是北极星距地球距离远远大于地球公转半径,所以地球公转带来的地轴变化可以忽略不计。于是一年四季里,我们看到在天空的北极星位置好像都是在正北方不动的,其实只是我们肉眼观察不到细微的变化,觉得地轴一直指向于北极星。
                                                                                                                                               ——百度百科



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