美国《纽约时报》是是美国严肃报刊的代表，长期以来拥有良好的公信力和权威性著称，1913年正式在美国出版发行，其新闻涵盖社会多个方面，当中文章更是囊括了丰富的词汇。所以可以通过阅读《纽约时报》来丰富自己的词汇量，从而更好地进备考。下面是小编推荐GRE阅读资料之宇宙中一定有过外星人。
Yes, There Have Been Aliens
没错，宇宙中一定有过外星人
LAST month astronomers from the Kepler spacecraft team announced the discovery of 1,284 new planets, all orbiting stars outside our solar system. The total number of such “exoplanets” confirmed via Kepler and other methods now stands at more than 3,000.
上个月，开普勒(Kepler)太空船团队中的天文学家们宣布他们已发现了1284颗新行星，它们都在太阳系外，沿着自己的轨道运行。经开普勒或其他途径所确认的“系外行星”如今已经超过3000颗。
This represents a revolution in planetary knowledge. A decade or so ago the discovery of even a single new exoplanet was big news. Not anymore. Improvements in astronomical observation technology have moved us from retail to wholesale planet discovery. We now know, for example, that every star in the sky likely hosts at least one planet.
这代表人们对行星的认识有了革命性的飞跃。大约10年前，哪怕只发现一颗新的系外行星都是重大新闻。如今却已经不是如此了。天文观测技术的进步令我们可以成批发现行星。举例来说，我们现在已经知道，夜空中的每一颗星星都很有可能拥有至少一颗行星。
But planets are only the beginning of the story. What everyone wants to know is whether any of these worlds has aliens living on it. Does our newfound knowledge of planets bring us any closer to answering that question?
但是行星只是这一切的开始。所有人都想知道，在那些世界上是否有外星人居住。我们新获得的关于行星的知识是否有助于我们回答这个问题?
A little bit, actually, yes. In a paper published in the May issue of the journal Astrobiology, the astronomer Woodruff Sullivan and I show that while we do not know if any advanced extraterrestrial civilizations currently exist in our galaxy, we now have enough information to conclude that they almost certainly existed at some point in cosmic history.
事实上，确实是有一点帮助的。我和天文学家伍德拉夫·苏利文(Woodruff Sullivan)在《天体生物学》(Astrobiology)杂志5月号上发表了一篇论文，指出虽然我们不知道银河系中是否存在先进的外星文明，但如今我们已经掌握信息，可以认为在宇宙历史的某个时点上，外星文明是肯定存在的。
Among scientists, the probability of the existence of an alien society with which we might make contact is discussed in terms of something called the Drake equation. In 1961, the National Academy of Sciences asked the astronomer Frank Drake to host a scientific meeting on the possibilities of “interstellar communication.” Since the odds of contact with alien life depended on how many advanced extraterrestrial civilizations existed in the galaxy, Drake identified seven factors on which that number would depend, and incorporated them into an equation.
科学家使用“德雷克等式”(Drake equation)这个术语来描述我们有可能与之取得联系的外星社会存在的几率。1961年，美国国家科学院请天文学家弗兰克·德雷克(Frank Drake)主持了一场科学座谈，主题是“星际沟通”的可能性。与外星生命取得联系的几率要看银河系中到底有多少先进的外星文明存在，因此德雷克列举了先进外星文明的存在所需要的七个因素，并把它们整合为一个等式。
The first factor was the number of stars born each year. The second was the fraction of stars that had planets. After that came the number of planets per star that traveled in orbits in the right locations for life to form (assuming life requires liquid water). The next factor was the fraction of such planets where life actually got started. Then came factors for the fraction of life-bearing planets on which intelligence and advanced civilizations (meaning radio signal-emitting) evolved. The final factor was the average lifetime of a technological civilization.
第一个因素是，每年会诞生多少颗新的恒星，第二个因素是，有多少颗恒星拥有行星。其三是，有每颗恒星所拥有的行星当中，到底有多少颗行星是运行在适宜生命存在的轨道上(假定生命的存在需要液态水)。第四个因素是，在这样的行星当中，究竟多少颗上已经有了真正的生命起源迹象。接下来的因素是，存在生命的行星当中，究竟有多少颗行星上存在智能生物，以及发达的文明(也就是说，要有无线电信号)。最后一个因素是，一个技术文明的平均寿命是多少 。
Drake’s equation was not like Einstein’s E=mc2. It was not a statement of a universal law. It was a mechanism for fostering organized discussion, a way of understanding what we needed to know to answer the question about alien civilizations. In 1961, only the first factor — the number of stars born each year — was understood. And that level of ignorance remained until very recently.
德雷克等式并不像爱因斯坦的 E=mc2。它并不是一个普遍的准则，只是一种进行系统化讨论的机制，可以帮助我们理解，在回答关于外星文明的问题的时候，我们究竟需要掌握什么知识。在1961年，只有第一个因素——每年会诞生多少颗新的恒星——是为人们所知的。其余几个因素人们直到前不久还不清楚。
That’s why discussions of extraterrestrial civilizations, no matter how learned, have historically boiled down to mere expressions of hope or pessimism. What, for example, is the fraction of planets that form life? Optimists might marshal sophisticated molecular biological models to argue for a large fraction. Pessimists then cite their own scientific data to argue for a fraction closer to 0. But with only one example of a life-bearing planet (ours), it’s hard to know who is right.
所以，不管人们了解多少知识，关于外星文明的讨论到最后总会变成乐观或悲观的各自表述。比如说，到底有多少行星上可以形成生命呢?乐观主义者们会建立精致的分子生物模型，证明这个比例很大。悲观主义者则会引述自己的科学数据，证明这个比例近乎零。但是，鉴于目前有生命的行星的例子只有一个(就是我们这个星球)，很难说究竟谁是对的。
更多双语阅读资料请点击》》GRE阅读资料之奥兰多枪案与特朗普的美国
Or consider the average lifetime of a civilization. Humans have been using radio technology for only about 100 years. How much longer will our civilization last? A thousand more years? A hundred thousand more? Ten million more? If the average lifetime for a civilization is short, the galaxy is likely to be unpopulated most of the time. Once again, however, with only one example to draw from, it’s back to a battle between pessimists and optimists.
再以文明的平均寿命为例。人类拥有无线电技术只有大约100年的历史。我们的文明还能存续多久?1000年?10万年?1000万年?如果一个文明的平均寿命很短，银河系很可能在大部分时间里是无人居住的。然而还是这个问题。我们手上只有一个例子，最后讨论又回到乐观主义者与悲观主义者之争。
But our new planetary knowledge has removed some of the uncertainty from this debate. Three of the seven terms in Drake’s equation are now known. We know the number of stars born each year. We know that the percentage of stars hosting planets is about 100. And we also know that about 20 to 25 percent of those planets are in the right place for life to form. This puts us in a position, for the first time, to say something definitive about extraterrestrial civilizations — if we ask the right question.
但是我们关于行星的新知识已经可以从这场讨论中去除一些不确定因素。如今，德雷克等式中已经有三个因素是已知的了。我们知道每年会诞生多少颗恒星。我们知道几乎100%的恒星都拥有行星。我们也知道，其中有20%到25%的行星都适宜产生生命。因此，关于外星文明，我们第一次可以说出一些确凿的东西——如果我们问对了问题的话。
In our recent paper, Professor Sullivan and I did this by shifting the focus of Drake’s equation. Instead of asking how many civilizations currently exist, we asked what the probability is that ours is the only technological civilization that has ever appeared. By asking this question, we could bypass the factor about the average lifetime of a civilization. This left us with only three unknown factors, which we combined into one “biotechnical” probability: the likelihood of the creation of life, intelligent life and technological capacity.
在我们最近的那篇论文中，我和苏利文博士在提出问题的时候，转变了德雷克等式的重点。我们的问题并不是“现在到底有多少外星文明存在”，而是“迄今为止，地球是宇宙中唯一出现过的技术文明，这个可能性有多大”。在这个问题中，我们可以把“文明的平均寿命”这个因素回避掉。这样一来就只有三个不确定因素了，我们可以把它们整合为一个“生物技术”的可能性问题：生命的诞生、智慧生命的诞生与掌握技术能力，这些究竟有多大的可能性。
You might assume this probability is low, and thus the chances remain small that another technological civilization arose. But what our calculation revealed is that even if this probability is assumed to be extremely low, the odds that we are not the first technological civilization are actually high. Specifically, unless the probability for evolving a civilization on a habitable-zone planet is less than one in 10 billion trillion, then we are not the first.
你可能会觉得这种可能性非常低，因此另一个技术文明存在的几率非常小。但是，我们的计算表明，就算这种可能性相当低，我们也很有可能不是宇宙中的第一个技术文明。具体来说，除非在一颗宜居行星上发展起一个文明的可能性小于10的22次方分之一，否则地球不可能是第一个技术文明。
To give some context for that figure: In previous discussions of the Drake equation, a probability for civilizations to form of one in 10 billion per planet was considered highly pessimistic. According to our finding, even if you grant that level of pessimism, a trillion civilizations still would have appeared over the course of cosmic history.
介绍一下这个数字的背景资料：在之前关于德雷克等式的讨论中，每100亿颗行星中能够诞生一个文明被认为是非常悲观的看法。根据我们的研究，就算以这个悲观的标准衡量，宇宙史上仍然有可能存在过1兆个文明。
In other words, given what we now know about the number and orbital positions of the galaxy’s planets, the degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational.
换言之，鉴于我们现在已经知道了银河系中有多少行星以及它们的轨道位置， 如果还要质疑先进外星文明存在过，这种悲观主义已经接近非理性的地步。
In science an important step forward can be finding a question that can be answered with the data at hand. Our paper did just this. As for the big question — whether any other civilizations currently exist — we may have to wait a long while for relevant data. But we should not underestimate how far we have come in a short time.
在科学当中，找到一个可以由现有数据解答的问题，也是一个重要的进步。我们的论文所做的就是这件事。至于说目前宇宙中是否存在其他文明这个大问题，我们可能要等待相当长的一段时间才能获得相关数据。但是我们不能低估人类在这样短的时期内取得了多么大的进展。
以上关于GRE阅读资料之宇宙中一定有过外星人的双语资料就为考生介绍到这里，外星人是否真的存在，还需要科学的证明!
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