英語聽力文摘宇宙生命奧秘

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The Habitable Zone

宇宙生命奧秘

適居帶(HZ)是天文學(xué)上給一種空間的名稱，指的是那里的情況有利于生物的存在，或許可以發(fā)現(xiàn)像地球這樣的生命體。有兩種區(qū)域是有可能的，一個是在行星系內(nèi)，另一個則存在于星系之中。在適合的區(qū)域內(nèi)的行星和天然衛(wèi)星是最佳的候選者，這些地球外的生命有能力生活在類似我們的環(huán)境下。天文學(xué)家相信生命最可能發(fā)生在像太陽系這樣的星周盤適居帶(CHZ)和大星系的星系適居帶 (GHZ)內(nèi)。適居帶也許是指"生命帶"、"綠帶"或"Goldilocks帶"(因為既不太熱也不太冷，就是剛好)。在我們的太陽系，適居帶被認(rèn)為從0.95天文單位延伸至1.37天文單位。

Y: Do you think there's life on other planets Don?

D: It seems perfectly reasonable that there would be Ya?l. what with how unfathomably large the universe is.Don't you think?

Y:I do.But then again, life is a tricky thing. So much has to fall into place for the conditions for life as we know it to be possible.For instance, a planet has to be just the right distance from the star it revolves around.

D:How is that?

Y:If it’s too close to its star, the heat from the star would cause any water on the planet to boil away. If it’s too far away, the opposite problem occurs: the cold temperature would cause water to freeze. The range of distance from a star that will allow water to remain a liquid is called the habitable zone.

D:So we Earthlings are lucky I guess that we are just the right distance away from the sun.

Y:Very lucky it seems.In 2007, scientists discovered the first two Earth-like planets outside our solar system that appear to be located near or within their star’s habitable zone. Previously discovered planets have had masses more akin to Jupiter’s. The planets orbit the same star and are known as Gliese 581c and Gliese 581d.

D:Wow,so there is other life out there?

Y:Not so fast, upon further investigation, it seems that Gliese 581d may be the only one of the two actually in the habitable zone, and its orbit seems to take it in and out of the zone. Not to mention as I said, a lot of factors must come into play for life to exist. Being within the habitable zone is just one of them.

譯文

Y:Don，你認(rèn)為其他行星上會有生命存在嗎?

D:似乎完全有理由相信有生命存在。宇宙如此之大，深不可測，不是嗎?

Y:的確如此。但是話又說回來，生命的存在是一件極其有難度的事。據(jù)我們所知，生命存在的可能性需要滿足眾多適合生存的條件。比如說，行星與其所圍繞旋轉(zhuǎn)的恒星之間的距離是否適當(dāng)。

D:這有什么關(guān)系?

Y:如果太近，來自恒星的熱量會導(dǎo)致行星上水分蒸發(fā)，與之相反，要是距離太遠(yuǎn)，溫度太低會致使水凍結(jié)。與恒星之間的距離要能保持水呈現(xiàn)的是液體狀態(tài)，這個范圍被稱作適居帶。

D:那我們地球豈不是很幸運，與太陽之間的距離正當(dāng)適宜。

Y:是非常的幸運。2007年，科學(xué)家們在太陽系以外首次發(fā)現(xiàn)兩顆類似地球，可能位于適居帶附近的行星，而之前發(fā)現(xiàn)的行星更類似于木星。這兩顆行星都圍繞格利澤581恒星轉(zhuǎn)動，因此他們被稱作格利澤581d和格利澤581c。

D:哇!那探索到有生命存在嗎?

Y:沒那么快。據(jù)進(jìn)一步調(diào)查研究發(fā)現(xiàn)，格利澤581d可能是二者中在適居區(qū)以內(nèi)的行星，而且其運行軌道使其在適居區(qū)內(nèi)游離。更何況正如我所說的，生命存在還有諸多因素要考慮，在適居區(qū)只是其中之一。

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