英語(yǔ)聽(tīng)力文摘 迅捷的外星人

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愛(ài)因斯坦的狹義相對(duì)論認(rèn)為物體的運(yùn)動(dòng)速度越接近光速，時(shí)間越慢。在1971年，物理學(xué)家理查德·基廷和喬伊·哈夫勒驗(yàn)證了這個(gè)假想。他們將4個(gè)極為精確的原子鐘放在一架普通航行的飛機(jī)上。飛行之后，這些原子鐘與放在地面的原子鐘相比的確慢了59納秒。它不僅證明狹義相對(duì)論完全正確，也說(shuō)明人們通過(guò)坐飛機(jī)來(lái)長(zhǎng)壽，理論上是可行的，所不同的是效果太微弱了。一個(gè)人在飛機(jī)上飛行80年的時(shí)間一共可以賺得400微秒。400微秒實(shí)際上只是0.0004秒。但是在粒子加速器里，狹義相對(duì)論所預(yù)言的時(shí)間膨脹效應(yīng)就不那么微弱了，在美國(guó)費(fèi)米試驗(yàn)室長(zhǎng)達(dá)40公里的粒子加速器中，次原子粒子可以被加速到光速的90%以上，在這樣的速度下，時(shí)間的變化明顯出現(xiàn)了。在正常情況下壽命很短的粒子，存在的時(shí)間大大延長(zhǎng)。這證明對(duì)這些粒子來(lái)說(shuō)，時(shí)間變慢了。

Since time slows down the closer you get to the speed of light, if alien spaceships could travel at light speed, wouldn't they take longer to get places?

We received a letter from one of our readers with a question about Einstein’s Theory of Relativity: Since time slows down the closer you get to the speed of light, if alien spaceships could travel at light speed, wouldn’t they take longer to get places?

Well, nothing that starts at a lower speed can ever make it to light speed, but theoretically you can come as close as you want. So to keep things simple, let’s say the flying saucers(飛碟) move at just under light speed. Let’s also say that their planet, Zork, is a hundred light years from Earth. How long does it take them to get from Zork to Earth? Just over one hundred years.

Now here’s the tricky part. Since the aliens on board the ship traveled so fast relative to us, time slowed to a crawl for them relative to the way it passed for us on Earth. In a hundred years’ Earth time, the zippy aliens may have only aged a few seconds.

Notice, though, that there’s no going back. Their fellow aliens on Zork who didn’t take the near-light speed trip are all one hundred years older now, too! If our Zorkian visitors turned right around and flew home again, when they got there, they would find it was now two hundred years later.

If humanity ever does build such awesome ships, the fact that time slows down for near-light speed travelers won’t make the ships themselves go any faster or slower. It will, however, make it possible for explorers to go to distant stars in their own lifetimes–just not in the lifetimes of anyone they left behind.

譯文：

迅捷的外星人

曾經(jīng)有位讀者來(lái)信詢問(wèn)了這樣一個(gè)關(guān)于愛(ài)因斯坦“相對(duì)論”的問(wèn)題：一旦時(shí)間的速度減緩，我們將接近光速，如果外星飛船以光速飛行，那不是需要更長(zhǎng)的時(shí)間才能到達(dá)目的地嗎?

事實(shí)上，沒(méi)有任何以低速運(yùn)轉(zhuǎn)的物體可以達(dá)到光速，但從理論上來(lái)說(shuō)，我們能夠與光速無(wú)限接近。簡(jiǎn)單來(lái)說(shuō)，我們假設(shè)宇宙飛碟以僅次于光速的速度飛行。再假如，外星人的星球?yàn)?ldquo;卓克”星球，距離地球一百光年，他們從“左克”星球到達(dá)地球需要多長(zhǎng)時(shí)間呢?僅需要一百年多點(diǎn)兒。

可是棘手的問(wèn)題出現(xiàn)了。既然外星飛碟的飛行速度相對(duì)我們來(lái)說(shuō)如此之快，對(duì)他們而言，時(shí)間的速度就如同爬行一般。地球上的一百年僅相當(dāng)于他們的數(shù)秒鐘而已。

值得注意的是，這一切卻是不可逆轉(zhuǎn)的。因?yàn)樵?ldquo;卓克”星球，那些沒(méi)有踏上近光速飛行之旅的同類(lèi)們也將一百歲了。如果我們的“左克”星球來(lái)訪者抵達(dá)后立即掉頭返回，當(dāng)他們到達(dá)自己的星球，那也已經(jīng)是兩百年以后了。

如果人類(lèi)真能制造出那樣的飛船，事實(shí)是對(duì)于那些近光速飛行的人來(lái)說(shuō)時(shí)間的速度會(huì)變慢，但那不會(huì)使得飛船本身的速度加快或減慢。正因?yàn)槿绱耍诫U(xiǎn)家們可能在他們的有生之年到達(dá)遙遠(yuǎn)的外星球，但是請(qǐng)注意，這個(gè)有生之年僅僅是他們的，而不是與留在地球的其他人共享的。