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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]

11.For light to travel across the solar system, it will take_______.

[A] a year [B] nearly a day [C] two months [D] thirty minutes

12.The fact that it will never be possible to converse with someone on another planet shows that________

[A] radio messages do not travel fast enough

[B] no object can ever travel faster than light

[C] western culture has a special idea of communication

[D] certain universal laws cannot be prevailed against

13.Confronted with the new order of cosmic reality, many educated men________.

[A] become ignorant savage again [B] find the “time barrier” unbearable

[C] will not combine solar and stellar space[D] cannot adapt to the abrupt change of scale

14.Conservative scientists who deny that cosmic gulfs can ever be crossed will________

[A] laugh at the very idea of flight [B] learn a lesson as they did ten years ago

[C] find space travel beyond their reach[D] oppose the fundamental scientific laws

15.The author of the passage intends to show__________.

全文翻译

神奇的电话和电视网络将整个世界连结在一起，使所有的人都成了邻居，但是却不能延伸到宇宙中。你永远不可能和另一个星球上的人进行对话。即使有今天的无线电设备，信息传播也需要好几分钟，有时候甚至好几个小时，因为无线电和光波都是以每秒186, 000英里的有限速度传播。

20年后你能够听来自火星上的朋友说话，但是话从他口中说出至少要经过三分钟你才可以听到，你的回答也将经过相同的时间才能到达他耳中。在这样的状况下，交换语言信息是可能的，但是不可能对话。

对于一个认为即刻交流理所当然，并将其视为文明生活完整结构的一部分的文化来说，这种“时间障碍”可能会有深刻的心理影响。时间障碍(即无法和外星人进行对话)永远提醒我们不是所有的技术都能战胜普遍规律和限制。看起来非常确定的事情是：没有信号，更不用说物质，可以比光传播的速度快。

作为时空结构的一部分，光速是终极速度极限。在太阳系狭小的范围内，它不会给我们带来太严重的不便。最糟糕的情况也就是20小时，即无线电信号越过最远的冥王星的轨迹的时间。

正是当我们走到太阳系的界限之外的时候，我们开始面对着一个全新的宇宙秩序。即使在今天，许多在别的方面受过教育的人，像只能数到三而把三以上的数字都统称为四的野人，他们无法明白太阳系和恒星系的巨大不同。前者是围绕我们邻近的世界即行星的宇宙，后者是围绕那些遥远的恒星的宇宙。(后者比前者)确实大几百万倍，地球上的事物在规模上没有这样巨大的变化。

许多保守的科学家惊讶于这些宇宙鸿沟之大，因此否认跨越它们的可能性。有些人永远也不会进步：他们60年前怀疑飞行的可能性，10年前耻笑飞往其他行星的想法，现在又满有把握地说恒星是我们永远不能及的。他们再一次地错了，因为他们没有领悟我们这一时代的教训——如果某些东西从理论上说是可能的，并且没有一些基本的科学法则反对它的实现的话，它早晚都会实现。

有一天，我们会发现一种真正有效的航天器驱动方式。每一个技术发明都会发展到极限，而宇宙飞船的最终速度是光速。它们永远不会达到这个速度，但是它们将会与这个速度非常接近。那时，离地球最近的恒星用不了5年就可以到达。

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