萬物簡史 第29期:走進太陽系(7)

　　And how far is that exactly? It's almost beyondimagining. Space, you see, is just enormous—justenormous. Let's imagine, for purposes of edificationand entertainment, that we are about to go on ajourney by rocketship. We won't go terribly far—justto the edge of our own solar system—but we need toget a fix on how big a place space is and what asmall part of it we occupy.

　　這到底有多遠?幾乎難以想像。你看，空間大得不得了--簡直大得不得了。出于了解和娛樂的目的，我們來想像一下，我們就要乘火箭飛行器進行旅行。我們不會走得太遠--只到我們自己太陽系的邊緣--不過，我們先要明白：空間是個多么大的地方，我們占據(jù)的是個多么小的部分。

　　Now the bad news, I'm afraid, is that we won't be home for supper. Even at the speed of light,it would take seven hours to get to Pluto. But of course we can't travel at anything like thatspeed. We'll have to go at the speed of a spaceship, and these are rather more lumbering. Thebest speeds yet achieved by any human object are those of the Voyager 1 and 2 spacecraft,which are now flying away from us at about thirty-five thousand miles an hour.

　　哎呀，恐怕是壞消息，我們回不了家吃晚飯了。即使以光的速度(每秒30萬公里)前進，也要花7個小時才能到達冥王星。而且，我們當(dāng)然無法以這種速度進行旅行。我們不得不以宇宙飛船的速度前進。這個速度就很慢了。任何人造物體所能達到的最高速度是"旅行者1號"和"旅行者2號"宇宙飛船的速度，它們現(xiàn)在正以每小時5.6萬公里的速度飛離我們。

　　The reason the Voyager craft were launched when they were (in August and September 1977)was that Jupiter, Saturn, Uranus, and Neptune were aligned in a way that happens only onceevery 175 years. This enabled the two Voyagers to use a "gravity assist" technique in whichthe craft were successively flung from one gassy giant to the next in a kind of cosmic versionof "crack the whip." Even so, it took them nine years to reach Uranus and a dozen to cross theorbit of Pluto.

　　當(dāng)時(1977年8月和9月)之所以發(fā)射"旅行者"號飛船，是因為木星、土星、天王星和海王星排成了一條直線，這種現(xiàn)象每隔175年才發(fā)生一次。這就使得兩艘"旅行者"號飛船能夠利用"引力幫助"技術(shù)，以一種宇宙甩鞭的形式，被從一顆氣態(tài)巨星連續(xù)甩到下一顆氣態(tài)巨星。即使這樣，它們也要花9年時間才能到達天王星，要花12年時間才能越過冥王星的軌道。

　　The good news is that if we wait until January 2006 (which is when NASA's New Horizonsspacecraft is tentatively scheduled to depart for Pluto) we can take advantage of favorableJovian positioning, plus some advances in technology, and get there in only a decade or so—though getting home again will take rather longer, I'm afraid. At all events, it's going to be along trip.

　　好的消息是，要是我們等到2006年1月(這是美國國家航空和航天局暫定向冥王星發(fā)射"新地平線"號宇宙飛船的時間)，我們就可以利用有利的木星定位法，加上一些先進的技術(shù)，只用10年左右的時間便能抵達那里--雖然再次回到家里恐怕要花上相當(dāng)長的時間。