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Those planets are all going to be so hot, and you can't develop something as complex as life.
那些星球都太熱了，如生命這類復(fù)雜事物根本無法在那里誕生。
Scientists have gone back to the drawing board, looking to find worlds capable of supporting life, small rocky planets like earth.
科學(xué)家們重新開始了尋找，可支持生命的世界的工作，他們的目標(biāo)是類似地球的小型巖石行星。
We don't know that life has to evolve on the surface of small rocket planets. But we know it did once here on earth. And so it's a reasonable place to start the search.
我們不知道生命是不是，只有在巖石行星上才能出現(xiàn)，但我們知道它在地球上誕生了，所以在這種地方開展搜索是很明智的。
Earth is important, because we know that this little planet had everything it needed to create life. And if a distant world has similar conditions, there's at least a possibility life could emerge there too.
地球很重要，因?yàn)槲覀冎溃齽偤脫碛幸磺袆?chuàng)造生命所需的，如果一個(gè)遙遠(yuǎn)世界也有類似的條件，那么那里至少有可能也出現(xiàn)生命。
If you were to give a biologist a piece of paper and say write down on every line something you need for life.
如果你給生物學(xué)家一張紙，并讓他列出他認(rèn)為生命所需的東西。
He'll say you need energy source, you need oxygen, you need water, you need carbon, you need organic compounds, you need amino acids, you need all the stuff.
他們會說那需要能源，氧氣，水，碳，有機(jī)化合物，氨基酸等等所有的一切。
There is a long list of factors that make our earth special and perfectly suited for life. But the most important is its distance from our energy source, the sun.
有一長串的東西使我們的地球與眾不同并且適宜生命存在，但最重要的是地球和我們能量來源的距離—太陽。
At 93 million miles away the earth is at just the right place for water to exist as a liquid. So why is liquid water important?
離地球9300萬英里遠(yuǎn)，地球所處的位置剛剛好，使得水能以液態(tài)形式存在，那么為什么液態(tài)水這么重要呢？
Imagine a world, so much hotter than the earth, there are no oceans, no liquid water all on its surface.
想象一個(gè)比地球熱得多的地方，那里地表上根本沒有海洋，沒有液態(tài)水。
Such a place would be like a desert. Without water, there is nothing to let the grains in sand interact.
這樣的地方會像一個(gè)沙漠，沒有水，就沒有東西可以使這些沙粒相互作用。
And in the same way without water, there is nothing to allow the atoms, the carbon and oxygen, and trace elements to form the molecules that would give rise to the chemistry of life.
同樣的沒有水就沒有東西可以使原子，碳，氧氣，和各種元素形成可產(chǎn)生生命的化學(xué)反應(yīng)的分子。
On the other hand, on a world much colder than the earth, water can only exist as ice, and we have another problem.
但另一方面，在一個(gè)比地球冷得多的地方，水只能以冰的形式存在，這就產(chǎn)生了另一個(gè)問題。
This frozen block of sand has all the grains in sand locked together. They can't move around and interact.
這個(gè)凍住的沙塊有許多被困住的沙粒，它們無法移動(dòng)并相互作用。
Just the same way that on a frozen world, the atoms in molecules can't move around and interact to from the chemistry necessary for life.
同樣在一個(gè)冰凍的世界，原子和分子無法移動(dòng)或相互作用，來形成生命必須的化學(xué)反應(yīng)。
But if temperatures and conditions are just right like here on earth, you get liquid water.
但如果溫度和其他條件都很合適，比如在地球上就能有液態(tài)水。
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