第43课

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We must conclude from the work of those who have studied the origin of life,

从研究生命起源的那些人的工作中，我们必须得出结论，

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that given a planet only approximately like our own, life is almost certain to start.

只要有一颗与我们地球大致相似的行星，生命几乎肯定会开始。

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Of all the planets in our solar system, we are now pretty certain the Earth is the only one on which life can survive.

在我们太阳系的所有行星中，我们现在非常确定地球是唯一一个生命可以存活的行星。

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Mars is too dry and poor in oxygen, Venus far too hot, and so is Mercury,

火星太干燥，氧气稀少；金星和水星都太热，

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and the outer planets have temperatures near absolute zero and hydrogen-dominated atmospheres.

而外行星的温度接近绝对零度，大气层以氢为主。

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But other suns, start as the astronomers call them, are bound to have planets like our own, and as is the number of stars in the universe is so vast,

但是其他太阳，天文学家称之为恒星，必定有像我们地球一样的行星，而且宇宙中恒星的数量如此之多，

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this possibility becomes virtual certainty.

这种可能性几乎成了必然。

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There are one hundred thousand million starts in our own Milky Way alone,

仅在我们的银河系中就有1000亿颗恒星，

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and then there are three thousand million other milky ways or galaxies, in the universe.

而宇宙中还有30亿个其他星系。

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so the number of stars that we know exist is now estimated at about 300 million million million.

因此，我们已知存在的恒星数量现在估计约为300万亿亿。

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Although perhaps only 1 percent of the life that has started somewhere will develop into highly complex and intelligent patterns,

尽管在某个地方开始的生命中，可能只有1%会发展成高度复杂和智能的模式，

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so vast is the number of planets, that intelligent life is bound to be a natural part of the universe.

但行星的数量如此之多，以至于智慧生命必然是宇宙的自然组成部分。

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If then we are so certain that other intelligent life exists in the universe, why have we had no visitors from outer space yet?

既然我们如此确定宇宙中存在其他智慧生命，那为什么我们还没有迎来外太空的访客呢？

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First of all, they may have come to this planet of ours thousands or millions of years ago,

首先，他们可能在几千或几百万年前就已经来到过我们的星球，

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and found our then prevailing primitive state completely uninteresting to their own advanced knowledge.

并发现我们当时普遍存在的原始状态对于他们自身先进的知识来说完全不感兴趣。

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Professor Ronald Bracewell, a leading American radio astronomer,

罗纳德·布雷斯韦尔教授，一位杰出的美国射电天文学家，

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argued in Nature that such a superior civilization, on a visit to our own solar system,

在《自然》杂志上提出，这样一个更高级的文明，在访问我们太阳系时，

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may have left an automatic messenger behind to await the possible awakening of an advanced civilization.

可能会留下一个自动信使，以等待一个先进文明的可能觉醒。

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Such a messenger, receiving our radio and television signals,

这样一个信使，在接收到我们的无线电和电视信号后，

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might well re-transmit them back to its home-planet,

很可能会将它们重新发送回它的母星，

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although what impression any other civilization would thus get from us is best left unsaid.

尽管其他文明会因此从我们这里得到什么样的印象最好还是不提为妙。

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But here we come up against the most difficult of all obstacles to contact with people on other planets

但在这里，我们遇到了与外星球人接触所有障碍中最困难的一个

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-- the astronomical distances which separate us.

——将我们分开的巨大天文距离。

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As a reasonable guess, they might, on an average, be 100 light years away.

合理猜测，他们平均可能在100光年之外。

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(A light year is the distance which light travels at 186,000 miles per second in one year, namely 6 million million miles.)

(一光年是光以每秒18.6万英里的速度在一年中旅行的距离，即6万亿英里。)

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Radio waves also travel at the speed of light,

无线电波也以光速传播，

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and assuming such an automatic messenger picked up our first broadcasts of the 1920's,

假设这样一个自动信使接收到了我们20世纪20年代的首次广播，

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the message to its home planet is barely halfway there.

那么它传回家园星球的信息才刚刚走了一半的路程。

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Similarly, our own present primitive chemical rockets,

同样地，我们目前原始的化学火箭，

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though good enough to orbit men, have no chance of transporting us to the nearest other star,

尽管足以将人类送入轨道，却没有机会将我们运送到最近的恒星，

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four light years away, let alone distances of tens or hundreds of light years.

距我们四光年之遥，更不用说几十或几百光年的距离了。

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Fortunately, there is a 'uniquely rational way' for us to communicate with other intelligent beings,

幸运的是，我们有一种“唯一理性方式”可以与其他智慧生物交流，

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as Walter Sullivan has put it in his excellent book,

正如沃尔特·沙利文在他的优秀著作中所说，

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We Are not Alone.

《我们并不孤单》。

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This depends on the precise radio frequency of the 21-cm wavelength, or 1420 megacycles per second.

这取决于21厘米波长，即每秒1420兆赫兹的精确无线电频率。

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It is the natural frequency of emission of the hydrogen atoms in space and was discovered by us in 1951;

它是太空中氢原子的自然发射频率，由我们于1951年发现；

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it must be known to any kind of radio astronomer in the universe.

宇宙中任何一种射电天文学家都必定知道它。

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Once the existence of this wave-length had been discovered,

一旦这种波长被发现，

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it was not long before its use as the uniquely recognizable broadcasting frequency for interstellar communication was suggested.

很快就有人建议将其用作星际通信的独特可识别广播频率。

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Without something of this kind,

如果没有这种东西，

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searching for intelligences on other planets would be like trying to meet a friend in London without a pre-arranged rendezvous

寻找其他行星上的智慧生命，就像在伦敦没有事先约定地点就试图与朋友见面一样，

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and absurdly wandering the streets in the hope of a chance encounter.

荒唐地在街上闲逛，希望能偶然相遇。