英語聽力文摘458 外太空有人嗎

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The Fermi Paradox

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.

費爾米悖論

早在1950年，諾貝爾獎獲得者恩里克.費爾米正與他的朋友吃午餐。他們的話題轉到是否可能存在外太空生命上。按照那個受歡迎故事的說法，當時費米爾沉默了一會，然后問到了這個簡單而又深刻的問題：他們都去哪了?

現在，那個問題被稱為是“費米爾悖論”。有個版本是這樣的：在銀河系里，有幾千億顆恒星。假設說那些恒星半數周圍有行星。

然后假設和我們的太陽系一樣，每顆恒星周圍每十顆行星有一顆或兩顆有利于形成生命。假設那的生命和地球上的一樣，要花費十億年才開始形成。再假設更高級形式的生命要再花幾十億年才能進化，就如地球上所經歷的那樣。

沒有一項有問題。銀河系已經近一百億光年了。即使很保守的估計，它應該還是擠滿了生命——甚至是智能生命。后來的卡爾.薩根計算了一下，目前應該大約有100萬先進文明在那了。

那么他們在哪呢?把小報故事放一邊看，現在還沒有任何角度的科學證據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?證據應該到處都是。

那就是“費米爾悖論”。你是否相信有飛碟都不重要。這只是一個簡單的估計：假如讓我們知道有關我們所在的恒星，行星的知識，還有生命如何進化的，那就可以推斷別處可能發(fā)生什么。可是，還沒有外星文明的跡象呢。

我們的思想一定是哪出了問題。但是是什么問題呢?下次再說吧。