歌词
Lesson 43
第43课
Are there strangers in space?
宇宙中有外星人吗？
What does the 'uniquely rational way' for us to communicate with other intelligent beings in space depend on?
我们与宇宙中其他智力生命交流的“唯一合理的方法”所依赖的是什么？
We must conclude from the work of those who have studied the origin of life,
根据研究生命起源的人们所做的工作，我们必然会得出这样的结论：
that given a planet only approximately like our own, life is almost certain to start.
如果设想有一颗行星和我们地球的情况基本相似，那几乎肯定会产生生命。
Of all the planets in our own solar system, we are now pretty certain the Earth is the only one on which life can survive.
我们目前可以肯定的是，在我们太阳系的所有行星中，地球是生命能存在的唯一行星。
Mars is too dry and poor in oxygen, Venus far too hot, and so is Mercury,
火星太干燥又缺氧，金星太热，水星也一样，
and the outer planets have temperatures near absolute zero and hydrogen-dominated atmospheres.
其它外围行星的温度都接近绝对零度，而且它们的大气成分主要是氢气。
But other suns, stars 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，其它太阳，即天文学家所说的恒星，（其周围）肯定也会有像我们地球一样的行星。因为宇宙中恒星数目极其庞大，
this possibility becomes virtual certainty.
所以存在着有生命的行星的这种可能性几乎是确定无疑的。
There are one hundred thousand million stars in our own Milky Way alone,
仅我们银河系就有1000亿颗恒星，
and then there are three thousand million other milky ways or galaxies, in the universe.
而且在宇宙中还有30亿个其它天河或者星系。
so the number of stars that we know exist is now estimated at about 300 million million million.
因此，我们所知道的现有的恒星数目估计约有310^20颗。
Although perhaps only 1 percent of the life that has started somewhere will develop into highly complex and intelligent patterns,
虽然在宇宙中某个地方产生的生命只有1%的可能性会发展成高度复杂的有智力的生命形态，
so vast is the number of planets, that intelligent life is bound to be a natural part of the universe.
但行星的数目是如此巨大，因此有智力的生命必然是宇宙的自然组成部分。
If then we are so certain that other intelligent life exists in the universe, why have we had no visitors from outer space yet?
既然我们如此坚信宇宙中存在着其他有智力生命，那么为什么我们未曾见到外太空来访的客人呢？
First of all, they may have come to this planet of ours thousands or millions of years ago,
首先，他们可能在数千年或数百万年前就已经来过我们地球，
and found our then prevailing primitive state completely uninteresting to their own advanced knowledge.
并且发现我们当时普遍存在的原始状态与他们先进的知识相比是索然无味的。
Professor Ronald Bracewell, a leading American radio astronomer,
美国的一位主要的射电天文学家罗纳德·布雷斯韦尔教授，
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的观点：假如有如此高级文明访问了我们太阳系，
may have left an automatic messenger behind to await the possible awakening of an advanced civilization.
很可能会在离开时留下自动化信息装置，等待先进文明的觉醒。
Such a messenger, receiving our radio and television signals,
这种自动化信息装置，在接收到我们的无线电和电视信号后，
might well re-transmit them back to its home-planet,
完全有可能把这些信号发送回原来的行星，
although what impression any other civilization would thus get from us is best left unsaid.
至于其他文明行星对我们地球会有什么印象，还是暂时不说为好。
But here we come up against the most difficult of all obstacles to contact with people on other planets
但是我们所遇到的阻碍我们与其他行星居民联系的最大困难，
-- the astronomical distances which separate us.
是分隔我们的天文距离。
As a reasonable guess, they might, on an average, be 100 light years away.
据合理估计，外星人离我们的平均距离有100光年那么远。
(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186000英里每秒的速度传播一年的距离，即六万亿英里。）
Radio waves also travel at the speed of light,
无线电波也是以光速传播的，
and assuming such an automatic messenger picked up our first broadcasts of the 1920's,
假定外星人的这种自动化装置接收到了我们20世纪20年代的第一次广播信号，
the message to its home planet is barely halfway there.
那么这个信号在发送回原来的行星的途中才刚走了一半路程。
Similarly, our own present primitive chemical rockets,
同样我们目前所用的原始的使用化学燃料的火箭，
though good enough to orbit men, have no chance of transporting us to the nearest other star,
虽然可以把我们送上轨道，但还不足以把我们送到离我们最近、相距约四光年的其他恒星上去，
four light years away, let alone distances of tens or hundreds of light years.
更不用说几十或者几百光年远的地方了。
Fortunately, there is a 'uniquely rational way' for us to communicate with other intelligent beings,
幸运的是，有一种我们可以和其他有智力生命通讯联系的“唯一合理的方法”，
as Walter Sullivan has put it in his excellent book,
正如沃尔特·沙利文在其杰作
We Are not Alone.
《我们并不孤独》中阐述的。
This depends on the precise radio frequency of the 21-cm wavelength, or 1420 megacycles per second.
这种通讯方法要依靠波长为21厘米，频率精确为每秒1420兆周的无线电波。
It is the natural frequency of emission of the hydrogen atoms in space and was discovered by us in 1951;
这个频率是宇宙中氢原子所发射的电磁波的本征频率，是在1951年被人类发现的。
it must be known to any kind of radio astronomer in the universe.
这个频率是任何射电天文学家都必定熟悉的。
Once the existence of this wave-length had been discovered,
一旦这种波长的电磁波的实际存在被发现，
it was not long before its use as the uniquely recognizable broadcasting frequency for interstellar communication was suggested.
提出把这种唯一的传播频率可检测的电磁波用于星际交流也就为期不远了。
Without something of this kind, searching for intelligences on other planets would be like trying to
如果没有这种手段，要想寻觅其他星球上的智力生命，
meet a friend in London without a pre-arranged rendezvous and absurdly wandering the streets in the hope of a chance encounter.
就如同去伦敦见一位朋友，事先未约定地点，而荒唐地在街上游逛，以期碰巧遇上一样。
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