評論
打印
Are aliens going to eat us?
外星人會來吃我們嗎？
That's more of a science fiction question.
這更像是科幻小說里的才會出現的問題。
But science does havesomething to say here, and sometimes purely imaginativequestions are great tools for helping us think about how the realworld works.
但是在這個問題上我們還是可以尋求科學的答案。很多時候像這種純粹異想天開的問題卻能夠幫助我們更好地思考，更好地認識這個世界。
First, it's not strictly impossible.
首先，嚴格地說，這也不無可能。
Many scientists agree that theMilky Way galaxy is probably brimming with living things.
許多科學家都認為銀河系里可能到處都是生物，
That doesn't mean any of them aresmart enough to build interstellar spaceships, but let's assume they are.
但這并不是說它們就有能力建造星際間飛船。退一萬步說，就算它們有這個能力來建造星際間飛船，
Still, why are theyunlikely to eat us?
可是，它們又為什么要吃我們呢？
One reason lies in energy itself.
原因之一就在于能量本身。
The point of eating is to take in usable energy.
吃東西最主要就是為了攝入可用的能量。
A lion will expend a lot of energy running down azebra because, once it is caught, the calories contained in the meal far outweigh those expended in the chase.
一頭獅子可以耗掉大量的體力去追捕一匹斑馬，那是因為一旦抓住了那匹斑馬，它能攝入的斑馬肉里的能量大大超過了他在追捕過程中消耗的能量。
If this weren't true–say, if the zebra's body only had the caloric contentof a grape–then the energy expended would outweigh the energy gained, and the lion wouldlose out.
如果以上都不成立，假如斑馬肉里所含能量很少—少到根本就無法補充獅子追捕所耗能量，那么這頭獅子也只能是白白耗掉體力了。
Any alien predators would face the same problem.
既然有這樣的說法，那么食肉的外星人也會面對同樣的問題。
The amount of energy expended in building aspace program, fueling rockets, to say nothing of getting from one star to another, would behuge.
建造一個空間計劃，制造燃料火箭都需要消耗很多能量。更不用說從一個星球飛至另一個星球需要消耗更多的能量！
For any realistic technology it would far outweigh the benefit of just munching on people.It would be like climbing Mount Everest in order to pick a few berries.
與其獵食人類，還不如將那些能量用于更有實際意義的科技開發。其實獵食人類就像是辛辛苦苦攀上珠穆朗瑪卻只為摘些果子一樣大材小用，勞民傷財。
Some day we ourselves may travel to other planets. But any species that goes to such lengthsmerely to find food will find itself quickly exhausted.
也許某一天人類能夠踏上其他星球的土地。但是，任何一個為尋覓食物而踏上其他星球的物種終將認識到如此行徑只會消耗掉自己的能量——自取滅亡。
