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有些人说，爱情驱使世界运转；另一些并不那么罗曼蒂克而更为注重实际的人则说，不是爱情，而是金钱。但真实情况是，能量驱使世界运转。能量是生态系统的货币，只有当食物转变为能量，能量再用来获取更多的食物以供生长、繁殖和生存，生命才成为可能。所有生命都维系在这一循环上。
差不多众所周知，野生动物得以年复一年地生存下去，主要依靠在夏秋生长旺季尽量多吃，通常将多余的部分以脂肪的形式储存起来，然后到了冬天食物稀少的艰难时期，就用这些储备的脂肪来维持生命。然而，很可能鲜为人知的是，即使有储备的脂肪，野生动物在冬天消耗的能量比夏天要少。
一个很好的例证是白尾鹿。与大多数野生动物一样，鹿在营养丰富、食物充足的夏秋两季，繁殖、生长并储存脂肪。一只成熟健壮的母鹿，在十一月份怀胎，五月底或六月初生下两只幼鹿，这时，它必须寻找食物以获得必要的能量，这不仅是为了满足自身的需要，而且也是为了给幼鹿生产乳汁。产乳的最佳期也正是植物生长茂盛之时。这个时机选择得很好，因为乳汁生产是一个消耗能量的过程——它需要大量的食物，除非该地区具有丰富的食物资源，否则无法满足这种消耗。
夏季一天天过去，幼鹿日渐生长，它们变得较少依赖母鹿的乳汁，而更加依靠生长中的植物为其食物来源。雄性成鹿在夏天生长鹿角并养肥身体。在秋天，雄鹿和雌鹿都继续进食高质量食物，贮存体内脂肪，以备过冬。至于雌鹿和幼鹿，由于大量的能量用于产奶或生长，脂肪的积累速度不如完全成熟的雄鹿快。脂肪储备如同银行里的存款，供冬天食物来源不足时和有时由于雪深难以获得时，支取使用。
随着秋去冬来，还会发生其他变化: 幼鹿失去皮毛上的斑纹，所有鹿身上的毛长厚，颜色变深。毛皮的变化通常持续到9月。到??11月或12月天气变冷时，毛长得最厚。
此外，大自然还为鹿提供进一步的保护以帮助它们度过冬天——体内生理机能作相应调节，放慢新陈代谢，亦即生理活动的速度，从而降低能量的消耗。鹿变得有点动作迟缓、嗜睡。它们的心率减慢。冬眠的动物保存能量的习性胜过鹿。虽然鹿不冬眠，但他们随季节改变新陈代谢节奏的习性则是一样的。夏秋间，食物充裕的时候，鹿消耗较多的能量并储存脂肪。在冬天食物匮乏时，它们则消耗较少的能量并使用储存的脂肪。
1973-1974年间，第一次出现“能源危机”的时候，我正与家人住在明尼苏达州北部一处鹿群过冬地方的边缘地带。我们住在一个小屋里，观察鹿的生活习性，观察它们是如何随着冬季来临从夏秋的活动频繁状态而变得少动的，而到春暖雪融时，他们的活动又是如何增多起来的。
当时广播电台常告诫我们:“没有必要不开车，”“多穿衣服好保暖，并请调低锅炉上的恒温器。”这些话听起来既有趣又逗笑。因为与此同时，我们一直注视着鹿减少活动，长出越冬的厚毛，并减缓新陈代谢。几千年来，他们一贯如此。鹿减少生存所需的能耗以增加越冬生存的机会，从生物学角度来看是合情合理的。
当然，对鹿来讲，并非每个冬天都处于危难之中。如果冬天雪下得少，存活率和次年春天的繁殖力就高。但如果雪积得深，天气连续数周寒冷，鹿活动起来就得花费较多的能量，觅食会更难，这时它们就得更多地依赖其脂肪储备度过寒冬。如果这种情况持续太久，有些鹿就要死亡，只有体型最大最壮的，才有可能存活。对于像鹿这样四处自由奔走的野生动物来说，这是一条根本的生存规律。
的确，生命——还有死亡——周而复始，循环不已。当动物死亡的时候，他们的尸体转化为能量，变成食物，供其他生命形式使用。
如此循环，永不止息。
Unit 3 Text
Can you prove that the earth is round? Go ahead and try! Will you rely on your senses or will you have to draw on the opinions of experts?
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WHY DO WE BELIEVE THAT THE EARTH IS ROUND?
George Orwell
Somewhere or other — I think it is in the preface to saint Joan — Bernard Shaw remarks that we are more gullible and superstitious today than we were in the Middle Ages, and as an example of modern credulity he cites the widespread belief that the earth is round. The average man, says Shaw, can advance not a single reason for thinking that the earth is round. He merely swallows this theory because there is something about it that appeals to the twentieth-century mentality. Now, Shaw is exaggerating, but there is something in what he says, and the question is worth following up, for the sake of the light it throws on modern knowledge. Just why do we believe that the earth is round? I am not speaking of the few thousand astronomers, geographers and so forth who could give ocular proof, or have a theoretical knowledge of the proof, but of the ordinary newspaper-reading citizen, such as you or me.
As for the Flat Earth theory, I believe I could refute it. If you stand by the seashore on a clear day, you can see the masts and funnels of invisible ships passing along the horizon. This phenomenon can only be explained by assuming that the earth's surface is curved. But it does not follow that the earth is spherical. Imagine another theory called the Oval Earth theory, which claims that the earth is shaped like an egg. What can I say against it?
Against the Oval Earth man, the first card I can play is the analogy of the sun
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and moon. The Oval Earth man promptly answers that I don't know, by my own observation, that those bodies are spherical. I only know that they are round, and they may perfectly well be flat discs. I have no answer to that one. Besides, he goes on, what reason have I for thinking that the earth must be the same shape as the sun and moon? I can't answer that one either.
My second card is the earth's shadow: When cast on the moon during eclipses, it appears to be the shadow of a round object. But how do I know, demands the Oval Earth man, that eclipses of the moon are caused by the shadow of the earth? The answer is that I don't know, but have taken this piece of information blindly from newspaper articles and science booklets.
Defeated in the minor exchanges, I now play my queen of trumps: the opinion of the experts. The Astronomer Royal, who ought to know, tells me that the earth is round. The Oval Earth man covers the queen with his king. Have I tested the Astronomer Royal's statement, and would I even know a way of testing it? Here I bring out my ace. Yes, I do know one test. The astronomers can foretell eclipses, and this suggests that their opinions about the solar system are pretty sound. I am, to my delight, justified in accepting their say-so about the shape of the earth. If the Oval Earth man answers — what I believe is true — that the ancient Egyptians, who thought the sun goes round the earth, could also predict eclipses, then bang goes my ace. I have only one card left: navigation. People can sail ship round the world, and reach the places they aim at, by calculations which assume that the earth is spherical. I believe that finishes the Oval Earth man, though even
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then he may possibly have some kind of counter.
It will be seen that my reasons for thinking that the earth is round are rather precarious ones. Yet this is an exceptionally elementary piece of information. On most other questions I should have to fall back on the expert much earlier, and would be less able to test his pronouncements. And much the greater part of our knowledge is at this level. It does not rest on reasoning or on experiment, but on authority. And how can it be otherwise, when the range of knowledge is so vast that the expert himself is an ignoramus as soon as he strays away from his own specialty? Most people, if asked to prove that the earth is round, would not even bother to produce the rather weak arguments I have outlined above. They would start off by saying that \earth to be round, and if pressed further, would become angry. In a way Shaw is right. This is a credulous age, and the burden of knowledge which we now have to carry is partly responsible.
你能证明地球是圆的吗?来试试看吧！你将依靠你自己的智力还是不得不引用专家的观点呢? 我们为什么相信地球是圆的?
记得在什么地方——我想是在《圣女贞德》序言中——肖伯纳评论说，今天我们比在中世纪时更加轻信，更加迷信。而作为现代轻信的例证，他举出地圆说这一广为传播的信念。肖伯纳说，普通人举不出一条理由来说明为什么相信地球是圆的。他全盘接受这一理论，只是因为这一理论中有一种迎合20世纪心态的东西。
当然，肖伯纳是夸大其词了，但他说的也确实有些道理，这一问题值得进一步探讨，因为它会帮助人们看清现代知识的真实情况。我们究竟为什么会相信地球是圆的呢?我说的不是数千位天文学家、地理学家之类的人，他们可以用观察到的事实或用理论上的根据来证实这一点，我指的是如同你我之辈的报纸的普通读者。
至于“地平说”，我相信我能够加以驳斥。如果你在天气晴朗的日子站立海边，你可以看到船桅和烟囱沿着地平线移动而不见船体本身。只有假设地球表面呈曲线状，这一现象才能得到解释。但不能由此推断地球是球形的。设想另一个称做“地球卵形说”的理论吧，这一学说声称地球形如蛋状。对此，我能说什么加以反驳呢?
面对“地球卵形说”者，我能打的第一张牌是，可以根据太阳和月亮来类推。“地球卵形说”者立即回敬道，我无法根据自己的观察得知那些天体是球形的。我只能得知他们是圆的，而它们完全可能呈扁平
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的圆盘状。我对此无言以答。此外，他还会说，我凭什么理由认为地球一定与太阳和月亮的形状相同?对此，我同样无法解答。
我的第二张牌是地球的影子: 月食期间，地球投在月亮上的影子看上去呈圆形物体状。但“地球卵形说”者马上要问，我怎么知道月食是由地球的影子造成的呢?回答是，我并不知道，我只是照搬报刊文章和科普小册子上的说法而已。
小小交锋受挫，于是我打出一张王牌“Q”: 专家的看法。英国格林威治皇家天文台台长总该是权威了，他告诉我说地球是圆的。“地球卵形说”者用他的“K”牌压倒我的“Q”牌。天文台台长的话我检验过没有?再说，我知道怎么个检验法吗?这时候，我打出我的“爱司”。是的，我确实知道一个检验方法。天文学家能预报月食，这一点表明他们关于太阳系的看法是非常可信的。因此，令我高兴的是，我接受他们关于地球形状的论断是有道理的。
如果“地球卵形说”者反驳道——我以为他反驳得有理——认为太阳绕地球转的古代埃及人也能预言月食，那我的“爱司”牌便立刻化为乌有。我只剩下一张牌: 航海。人们可以扬帆绕地球航行而到达他们的目的地，其航程的计算，就是以地球是球形的假定为依据的。我相信这一下可以彻底击败“地球卵形说”者了。不过即便如此，他还可能有某种回击的办法。
由此可见，我认为地球是圆的，其根据是相当不牢靠的。然而这却是一点极其基本的知识。在别的大多数问题上，我只得更早地依赖专家的理论，且更少有办法检验他的结论了。我们的知识，其绝大部分都停留在这一水平上。它不是依靠推理或实验，而是依赖权威。可是，不这样，又有什么别的法子呢?知识的范围如此广博，一旦越出其专业范围，专家也会变成一无所知。对大多数人来说，如果要他们证明地球是圆的话，就连我上面概述的这些相当无力的论据，他们也不愿提供出来。他们一开始就会说: 谁都知道地球是圆的。要是再加追问，就会生气了。在某种程度上讲，肖伯纳是说对了，如今是一个轻信的时代。究其缘由，部分在于，我们现今必须掌握的知识实在太多了。
Unit 4
Text
On September 11, 2001, a series of suicide attacks on the United States took place. Foreign hijackers took control of four U.S. airliners. Two were crashed into the World Trade Center. The third aircraft was crashed into the Pentagon. The fourth, intended, it is thought, for another government target, crashed into a field, apparently after passenger resistance. This is the story of one of those passengers Flight 93:What I never know
Sunday, September 9, 2001, was a good day for the three of us. Emmy was just 11 weeks old and we were enjoying her enormously. After three miscarriages in two years, she was doubly precious to us. My husband, Jeremy, who was thinking of changing jobs, had gone on two interviews and felt they went well. Since Sunday
大学英语精读第三版第四册课本教学材料及课本教材翻译
