英語(yǔ)聽(tīng)力文摘458 外太空有人嗎
Back in 1950, the Nobel prize-winning physicist Enrico Fermi was having lunch with friends. Conversation turned to the possibility of extraterrestrial life. According to the popular story, Fermi fell silent for a moment and then asked the simple but profound question: “Where Is Everybody?”
That question is now known as the Fermi Paradox. A version goes like this. There are a few hundred billion stars in the Milky Way Galaxy. Suppose even half those stars have planets.
Then suppose only one or two of, say, ten planets per star is conducive to the formation of life, as is the case with our own solar system. Suppose life takes a billion years to get started, as happened on earth. Suppose the evolution of higher life forms takes another couple billion years, as it did here.
None of that would matter. The Milky Way galaxy is around ten billion years old. Even with very conservative estimates, it should still be swarming with life–even intelligent life. The late Carl Sagan calculated that there should be something like a million advanced civilizations out there right now.
So where are they? Tabloid stories aside, there’s no scientific evidence from any corner to suggest we aren’t alone in the Milky Way. But why not? The evidence should be everywhere.
That’s Fermi’s paradox. It has nothing to do with whether you believe in flying saucers or not. It’s a simple estimation: given what we know about our star, our planet, and how life evolved here, we can extrapolate to what probably happens elsewhere. And yet: there’s no sign of alien civilizations.
Something must have gone wrong in our thinking. But what? More next time.
費(fèi)爾米悖論
早在1950年，諾貝爾獎(jiǎng)獲得者恩里克.費(fèi)爾米正與他的朋友吃午餐。他們的話題轉(zhuǎn)到是否可能存在外太空生命上。按照那個(gè)受歡迎故事的說(shuō)法，當(dāng)時(shí)費(fèi)米爾沉默了一會(huì)，然后問(wèn)到了這個(gè)簡(jiǎn)單而又深刻的問(wèn)題：他們都去哪了?
現(xiàn)在，那個(gè)問(wèn)題被稱為是“費(fèi)米爾悖論”。有個(gè)版本是這樣的：在銀河系里，有幾千億顆恒星。假設(shè)說(shuō)那些恒星半數(shù)周?chē)行行恰?/p>
然后假設(shè)和我們的太陽(yáng)系一樣，每顆恒星周?chē)渴w行星有一顆或兩顆有利于形成生命。假設(shè)那的生命和地球上的一樣，要花費(fèi)十億年才開(kāi)始形成。再假設(shè)更高級(jí)形式的生命要再花幾十億年才能進(jìn)化，就如地球上所經(jīng)歷的那樣。
沒(méi)有一項(xiàng)有問(wèn)題。銀河系已經(jīng)近一百億光年了。即使很保守的估計(jì)，它應(yīng)該還是擠滿了生命——甚至是智能生命。后來(lái)的卡爾.薩根計(jì)算了一下，目前應(yīng)該大約有100萬(wàn)先進(jìn)文明在那了。
那么他們?cè)谀哪?把小報(bào)故事放一邊看，現(xiàn)在還沒(méi)有任何角度的科學(xué)證據(jù)表明我們不是銀河系中唯一存在的人類。但是為什么不是呢?證據(jù)應(yīng)該到處都是。
那就是“費(fèi)米爾悖論”。你是否相信有飛碟都不重要。這只是一個(gè)簡(jiǎn)單的估計(jì)：假如讓我們知道有關(guān)我們所在的恒星，行星的知識(shí)，還有生命如何進(jìn)化的，那就可以推斷別處可能發(fā)生什么?？墒?，還沒(méi)有外星文明的跡象呢。
我們的思想一定是哪出了問(wèn)題。但是是什么問(wèn)題呢?下次再說(shuō)吧。
