2017考研英语阅读理解下载 英语阅读理解150篇(7)

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　　“我还没有遇到一个值得克隆的人。” 克隆专家马克•威斯苏森在德克萨斯州农业机械大学空间狭小的实验室里说。

　　“那是一种愚蠢的尝试。”有趣的是，这种用来形容克隆人的言辞竟然来自一位已花费数百万美金试图克隆一只 13岁的名叫密斯的狗的人。到目前为止，他和他的团队还没有获得成功，尽管他们已经克隆出了两只牛并且正计划在短期内克隆出一只猫。他们可能会在年底成功克隆出密斯，也可能再过五年都不会成功。人类最亲密的朋友——狗的生殖系统似乎是现代科学中一个神秘的领域。

　　威斯苏森克隆动物的经验使他对克隆人的种种说法十分恼火。在研究“克隆密斯项目”的三年时间里，农业机械大学的团队使用了成百上千只犬科动物的卵，却仅仅获得了一打左右的带有密斯基因的胚胎，并且没有一个在被转移至克隆母体时存活下来。威斯苏森教授争辩道，在研究猫或牛的克隆试验中，对动物卵的浪费以及许多动物的自然性流产都是可以为人们所接受的，但是对于研究人来说就不行。他表示说，“克隆是十分低效的，而且也相当危险。”

　　尽管如此，克隆狗仍是一个商机，能带来丰厚的科研报酬。自从1997 年多利羊克隆成功后，威斯苏森教授在农业机械大学兽医学院的电话就频频响起。对于像密斯的神秘主人这样的消费者来说，高额的花销并不是什么难题，他只是希望匿名以保护自己的隐私。到目前为止，他已经投入了 370 万美金来资助这项研究，因为他想要一个密斯的孪生子在它死后继承其优良品质。但是这位主人知道，密斯的克隆体不一定能有与它一样的脾气秉性。在一份用途声明中，密斯的主人和农业机械大学的团队表示，他们“共同期待能研究密斯的克隆体与它本身的差异之处。”

　　用于实验的狗的命运将由威斯苏森教授的工作来决定。他知道即使有一只狗能成功怀孕，它的后代，如果能幸存下来，一出生就要面对其他克隆动物所面临的问题：像肺部和心脏发育不全造成的畸形以及体重问题等等。威斯苏森教授质问道，“在我们克隆动物的研究还没有接近成功时，为什么还想到要克隆人呢?”

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　　The marvelous telephone and television network that has now enmeshed the whole world, making all men neighbours, cannot be extended into space. It will never be possible to converse with anyone on another planet. Even with today's radio equipment, the messages will take minutes—sometimes hours—on their journey, because radio and light waves travel at the same limited speed of 186, 000 miles a second. Twenty years from now you will be able to listen to a friend on Mars, but the words you hear will have left his mouth at least three minutes earlier, and your reply will take a corresponding time to reach him. In such circumstances, an exchange of verbal messages is possible—but not a conversation. To a culture which has come to take instantaneous communication for granted, as part of the very structure of civilized life, this “time barrier” may have a profound psychological impact. It will be a perpetual reminder of universal laws and limitations against which not all our technology can ever prevail. For it seems as certain as anything can be that no signal—still less any material object—can ever travel faster than light. The velocity of light is the ultimate speed limit, being part of the very structure of space and time. Within the narrow confines of the solar system, it will not handicap us too severely. At the worst, these will amount to twenty hours—the time it takes a radio signal to span the orbit of Pluto, the outer-most planet. It is when we move out beyond the confines of the solar system that we come face to face with an altogether new order of cosmic reality. Even today, many otherwise educated men—like those savages who can count to three but lump together all numbers beyond four—cannot grasp the profound distinction between solar and stellar space. The first is the space enclosing our neighbouring worlds, the planets; the second is that which embraces those distant suns, the stars, and it is literally millions of times greater. There is no such abrupt change of scale in the terrestrial affairs. Many conservative scientists, appalled by these cosmic gulfs, have denied that they can ever be crossed. Some people never learn; those who sixty years ago scoffed at the possibility of flight, and ten years ago laughed at the idea of travel to the planets, are now quite sure that the stars will always be beyond our reach. And again they are wrong, for they have failed to grasp the great lesson of our age—that if something is possible in theory, and no fundamental scientific laws oppose its realization, then sooner or later it will be achieved. One day we shall discover a really efficient means of propelling our space vehicles. Every technical device is always developed to its limit and the ultimate speed for spaceships is the velocity of light. They will never reach that goal, but they

　　will get very near it. And then the nearest star will be less than five years voyaging from the earth.[514 words]