英語(yǔ)聽(tīng)力文摘流星與地球運(yùn)動(dòng)

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The Front End of the Earth

火流星看上去非常明亮，像條閃閃發(fā)光的巨大火龍，發(fā)著“沙沙”的響聲，有時(shí)還有爆炸聲。有的火流星甚至在白天也能看到。火流星的出現(xiàn)是因?yàn)樗牧餍求w質(zhì)量較大(質(zhì)量大于幾百克)，進(jìn)入地球大氣后來(lái)不及在高空燃盡而繼續(xù)闖入稠密的低層大氣，以極高的速度和地球大氣劇烈摩擦，產(chǎn)生出耀眼的光亮，并且通常會(huì)在空中走出“S”型路徑。火流星消失后，在它穿過(guò)的路徑上，會(huì)留下云霧狀的長(zhǎng)帶，稱(chēng)為“流星余跡”;有些余跡消失得很快，有的則可存在幾秒鐘到幾分鐘，甚至長(zhǎng)達(dá)幾十分鐘。

Enjoy star gazing?Then this Moment of Science is for you!

On a previous show we mentioned how not all shooting stars(流星) have the same speed. Some disappear almost immediately, while others make a nice slow line across the sky.

If you enjoy watching the slow ones, there is a way of upping your chances of seeing them. Go out just after sunset.That's because the slowest meteors come in the evening and the fastest ones come in the morning, just before sunrise.

Can you guess why?The speeds of meteors we see are increased or decreased by the earth’s motion. If we (1)charge into them (2)head-on our speed is added to their speed. If, on the other hand, we are moving away from them, our speed is (3)subtracted from their speed.

Now imagine yourself standing at the north pole, facing the direction the earth is moving through space. You rise up magically, far enough away that you can see the whole planet rotating underneath you while you yourself remain stationary. Which direction is it turning? Counterclockwise. Where is the sunlight? From your perspective, it’s on the left side of the planet.

That means that the front of the planet, or the part that’s charging into oncoming meteors, is the place where morning is beginning for people on earth. The back of the planet, meaning the part that’s moving away from meteors, is where evening is beginning.

It may seem funny, but every morning when you look up into the sky, you are looking in the same direction as the planet is moving. In the evening you are looking the other way. And the speed of shooting stars confirms it!

譯文：

流星與地球運(yùn)動(dòng)

前面的文章中我們提到為什么不是所有流星都有相同的速度。有些幾乎立即就消失了，而有些拖著長(zhǎng)長(zhǎng)的尾巴穿過(guò)天空。

如果你喜歡觀看緩慢的流星，那么有一種方法可以增加你看到它們的幾率。日落后就出門(mén)。最慢的流星在夜晚出現(xiàn)，最快的流星出現(xiàn)在早晨，就在太陽(yáng)升起之前。

你猜猜為什么呢?我們看到的流星的運(yùn)動(dòng)速度隨著地球的運(yùn)動(dòng)情況而增減。如果地球正對(duì)著流星的方向運(yùn)動(dòng)，那么我們的運(yùn)速就會(huì)增加至它的運(yùn)動(dòng)速度中，反之，如果我們背向它們運(yùn)動(dòng)，那么它們的運(yùn)速中就會(huì)減去地球運(yùn)速這一部分。

現(xiàn)在想想你自己站在北極，面向地球穿過(guò)空間移動(dòng)的方向。你奇跡般地上升，遠(yuǎn)到可以看到整個(gè)地球在你的腳下轉(zhuǎn)動(dòng)，而你自己保持靜止。它是在向哪個(gè)方向運(yùn)動(dòng)呢?逆時(shí)針。太陽(yáng)光在哪里呢?從你的角度來(lái)看，在地球的左側(cè)。

這意味著在地球的前端，或者是在正對(duì)流星運(yùn)動(dòng)的地方，就是早晨的開(kāi)始。地球的背面，也就是背向流星運(yùn)動(dòng)的地方，就是夜晚的開(kāi)始。

這似乎非常有趣，但是每天早晨當(dāng)你仰望天空時(shí)，你就是望著與地球轉(zhuǎn)動(dòng)相同的方向。晚上，你就是望著相反的方向。流星的速度證實(shí)了這一點(diǎn)。

Notes:

(1)charge into 沖進(jìn);撞上：

The students charged into the classroom to greet their teacher.

學(xué)生們沖進(jìn)教室，向老師問(wèn)好。

(2)head-on ['hed'?n] adj.正面的;直接的;頭朝前的 adv.迎頭;頭朝前地;正面針對(duì)地

The cars met head-on.

兩輛汽車(chē)頭迎頭相撞。

(3)subtract from 減去

If you would make a man happy, don't add to his possessions but subtract from his desire.

如果你想使一個(gè)人快樂(lè)，不要增加他的財(cái)產(chǎn)，而是減少他的欲望。