如果你可以從地球上看到外星球，你便沒有必要去尋找證據(jù)。你只需要監(jiān)測大氣中的氧氣。



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選材／校對／翻譯：hqj5715
If you could see an alien planet from Earth, you wouldn't necessarily need to look for cities. You could just check for oxygen in the atmosphere. Oxygen in the atmosphere? What would that prove? Well, if there are aliens, they're undoubtedly different from what we're used to on Earth. But one thing we know is that oxygen is the same everywhere. So? So, oxygen gas is highly reactive. That means it combines very rapidly with other elements, such as carbon and hydrogen. Now when the Earth was formed, any free oxygen must have quickly combined with other elements to form less reactive compounds. None would have been left over in the atmosphere. No! Then where did it come from? The oxygen that we find in our atmosphere now has only been around since plants first evolved. Plants give off oxygen as a by-product, just as you and I give off carbon dioxide. Without life on Earth, there'd be no oxygen in the atmosphere. Aha! So if we find oxygen around some alien planet… That’s a good place to look for life.
如果你可以從地球上看到外星球，你便沒有必要去尋找證據(jù)。你只需要監(jiān)測大氣中的氧氣。 大氣中的氧氣？氧氣能夠證明什么？如果有外星人的話，毫無疑問他們和我們地球上的習慣不一樣。但是一件事?lián)覀兯谌魏蔚胤蕉际且粯拥?，那便是氧氣? 氧氣具有很高的活性。這表示其可以快速的與其它的成分結合，比如碳元素和氫元素。當?shù)厍蛐纬傻臅r候，任何自由氧一定會快速的和其他元素結合以便形成活性低得化合物。大氣中不會剩下任何的氧氣。 氧氣從何而來呢？ 在我們大氣中所發(fā)現(xiàn)的氧氣僅僅存在于地球剛開始形成的周圍。星球以副產品的形式釋放氧氣，就像你我釋放二氧化碳一樣。 沒有生命在地球上的話，大氣中便不會存在氧氣。因此，如若我們發(fā)現(xiàn)外星球周圍存在氧氣……那個地方將很可能存在生命。