# 第四册 Lesson 43 Are there strangers in space? 宇宙中有外星人吗？

## 一、课文原文

We must conclude from the work of those who have studied the origin of life, that given a planet only approximately like our own, life is almost certain to start. 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. Mars is too dry and poor in oxygen, Venus far too hot, and so is Mercury, and the outer planets have temperatures near absolute zero and hydrogen-dominated atmospheres. But other suns, stars as the astronomers call them, are bound to have planets like our own, and as the number of stars in the universe is so vast, this possibility becomes virtual certainty. There are 100,000 million stars in our own Milky Way alone, and then there are 3,000 million other Milky Ways, or galaxies, in the universe. So the number of stars that we know exist is now estimated at about 300 million million million.

Although perhaps only 1% of the life that has started somewhere will develop into highly complex and intelligent patterns, so vast is the number of planets, that intelligent life is bound to be a natural part of the universe.

If then we are so certain that other intelligent life exists in the universe, why have we had no visitors from outer space yet? First of all, they may have come to this planet of ours thousands or millions of years ago, and found our then prevailing primitive state completely uninteresting to their own advanced knowledge. Professor Ronald Bracewell, a leading American radio astronomer, argued in Nature that such a superior civilization, on a visit to our own solar system, may have left an automatic messenger behind to await the possible awakening of an advanced civilization. Such a messenger, receiving our radio and television signals, might well re-transmit them back to its home-planet, although what impression any other civilization would thus get from us is best left unsaid.

But here we come up against the most difficult of all obstacles to contact with people on other planets — the astronomical distances which separate us. As a reasonable guess, they might, on an average, be 100 light years away. (A light year is the distance which light travels at 186,000 miles per second in one year, namely 6 million million miles.) Radio waves also travel at the speed of light, and assuming such an automatic messenger picked up our first broadcasts of the 1920's, the message to its home planet is barely halfway there. Similarly, our own present primitive chemical rockets, though good enough to orbit men, have no chance of transporting us to the nearest other star, four light years away, let alone distances of tens or hundreds of light years.

Fortunately, there is a 'uniquely rational way' for us to communicate with other intelligent beings, as Walter Sullivan has put it in his excellent book, We Are not Alone. This depends on the precise radio frequency of the 21-cm wavelength, or 1420 megacycles per second. It is the natural frequency of emission of the hydrogen atoms in space and was discovered by us in 1951; it must be known to any kind of radio astronomer in the universe.

Once the existence of this wave-length had been discovered, it was not long before its use as the uniquely recognizable broadcasting frequency for interstellar communication was suggested. Without something of this kind, searching for intelligences on other planets would be like trying to meet a friend in London without a pre-arranged rendezvous and absurdly wandering the streets in the hope of a chance encounter.

— ANTHONY MICHAELIS, *Are There Strangers in Space?* from The Weekend Telegraph

## 二、重点词汇详解

| 单词 | 音标 | 词性 | 释义 | 用法说明 |
|------|------|------|------|----------|
| approximately | /əˈprɒksɪmətli/ | adv. | 大约，近似地 | given a planet approximately like our own |
| bound | /baʊnd/ | adj. | 一定的，必然的 | are bound to 必然会 |
| galaxy | /ˈɡæləksi/ | n. | 星系，银河系 | the Milky Way 银河系 |
| prevailing | /prɪˈveɪlɪŋ/ | adj. | 盛行的，普遍的 | prevailing primitive state 当时普遍的原始状态 |
| messenger | /ˈmesɪndʒə/ | n. | 信使 | automatic messenger 自动信使 |
| obstacle | /ˈɒbstəkl/ | n. | 障碍 | the most difficult of all obstacles |
| astronomical | /ˌæstrəˈnɒmɪkl/ | adj. | 天文的，巨大的 | astronomical distances 天文距离 |
| megacycle | /ˈmeɡəˌsaɪkl/ | n. | 兆周 | 1420 megacycles per second |
| emission | /ɪˈmɪʃn/ | n. | 发射，散发 | frequency of emission 发射频率 |
| interstellar | /ˌɪntəˈstelə/ | adj. | 星际的 | interstellar communication 星际通信 |
| rendezvous | /ˈrɒndɪvuː/ | n. | 约会，会面地点 | pre-arranged rendezvous 预先约定的会面地点 |

**固定搭配：**
- **be bound to**：必然会
- **come up against**：遇到（困难）
- **let alone**：更不用说
- **by chance**：偶然地

## 三、语法知识点

### 1. so...that... 倒装结构

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

so + adj. 置于句首，主谓倒装，加强语气。

| 正常语序 | 倒装语序 |
|---------|---------|
| The number is so vast that... | So vast is the number that... |

### 2. given 过去分词作条件状语

> **given** a planet only approximately like our own, life is almost certain to start

given = if one considers / assuming，表示"如果有、考虑到"。

### 3. let alone 递进否定

> have no chance of transporting us to the nearest other star, **let alone** distances of tens or hundreds of light years

let alone = 更不用说，表示递进否定。

### 4. it was not long before 不久

> **it was not long before** its use as the uniquely recognizable broadcasting frequency was suggested

it was not long before = 不久就……

## 四、重点句型分析

### 句型1：概率推理

> Although perhaps only 1% of the life...will develop into highly complex and intelligent patterns, **so vast is the number of planets, that** intelligent life is bound to be a natural part of the universe

- 让步：只有1%发展出智慧
- 逆转：行星数量如此庞大，智慧生命必然存在
- so...that... 倒装增强说服力

### 句型2：类比论证

> searching for intelligences on other planets would be like trying to meet a friend in London **without a pre-arranged rendezvous** and **absurdly wandering the streets** in the hope of a chance encounter

- 在伦敦无约定找人 = 在宇宙中无频率搜索
- 类比生动形象

### 句型3：反问与解答

> **why have we had no visitors** from outer space yet?

- 提出问题→三种可能解释
- 结构：可能已来过→距离障碍→通信方案

## 五、课文翻译

从研究生命起源的学者的工作中，我们必须得出结论：只要有一个大约像我们地球这样的行星，生命就几乎一定会出现。在我们太阳系的所有行星中，我们现在相当确定只有地球上有生命可以存活。火星太干燥且缺氧，金星太热，水星也是，而外行星的温度接近绝对零度，大气以氢为主。但其他太阳——天文学家称之为恒星——一定有像我们这样的行星，而且因为宇宙中恒星的数量如此庞大，这种可能性几乎成为确定性。仅我们的银河系就有1000亿颗恒星，而宇宙中还有30亿个其他银河系即星系。所以我们知道存在的恒星数量估计约为300万亿亿。

虽然也许只有1%在某个地方开始的生命会发展成高度复杂和智慧的模式，但行星的数量如此庞大，以至于智慧生命必然是宇宙的自然组成部分。

既然我们如此确定宇宙中存在其他智慧生命，为什么我们还没有外太空的访客呢？首先，他们可能在数千或数百万年前就来过我们这个星球，发现我们当时普遍的原始状态对他们先进的知识来说毫无吸引力。美国著名射电天文学家罗纳德·布雷斯韦尔教授在《自然》杂志上论证说，这样一个高级文明在访问我们太阳系时，可能留下了一个自动信使，等待可能出现的先进文明的觉醒。这样一个信使接收到我们的无线电和电视信号后，可能会把它们转发回它的母星，尽管其他文明由此对我们产生的印象还是不说为好。

但在这里我们遇到了与其他行星上的人联系的所有障碍中最困难的一个——分隔我们的天文距离。作为合理的猜测，它们平均可能在100光年之外。（一光年是光以每秒186,000英里的速度在一年中传播的距离，即6万亿英里。）无线电波也以光速传播，假设这样一个自动信使接收了我们在20世纪20年代的首次广播，信息到达其母星还不到一半路程。同样，我们目前原始的化学火箭虽然足以将人送入轨道，但根本没有可能将我们送到最近的另一颗恒星——4光年之外——更不用说几十或几百光年的距离了。

幸运的是，有一种"独特而合理的方式"让我们与其他智慧生物通信，正如沃尔特·沙利文在他优秀的著作《我们并不孤独》中所说的。这取决于21厘米波长或每秒1420兆周的精确无线电频率。这是太空中氢原子的自然发射频率，我们在1951年发现了它；宇宙中任何类型的射电天文学家都必须知道这一点。

一旦这个波长的存在被发现，不久就有人建议将它作为星际通信的独特可识别广播频率。没有这种东西，在其他行星上搜索智慧生命就像在伦敦没有一个预先约定的会面地点而荒唐地在大街上游荡，希望偶遇一个朋友。

## 六、语言点精讲

### 1. 写作手法：科学推理

- 从生命起源的概率推理→恒星数量→智慧生命必然存在
- 从问题（为什么没有访客）→障碍（距离）→解决方案（21厘米波长）

### 2. 逻辑结构

| 段落 | 主题 | 论证方式 |
|------|------|----------|
| 第一段 | 外星生命必然存在 | 概率推理+数据 |
| 第二段 | 智慧生命必然存在 | so...that... 倒装 |
| 第三段 | 为什么没有访客 | 假设推理 |
| 第四段 | 距离障碍 | 数据说明 |
| 第五段 | 通信方案 | 科学原理 |
| 第六段 | 频率的重要性 | 类比论证 |

### 3. 文化背景

- Ronald Bracewell：斯坦福大学射电天文学家
- 21厘米波长：氢原子的自然发射频率，是SETI（搜寻地外智慧生命）项目的核心频率
- Walter Sullivan《We Are Not Alone》：1964年出版的外星生命科普著作

### 4. 修辞分析

- "what impression...is best left unsaid"——幽默讽刺
- "like trying to meet a friend in London"——类比，生动
- "absurdly wandering the streets"——自嘲

## 七、课后练习要点

1. **词汇练习**：掌握 approximately、bound、galaxy、interstellar、rendezvous 等核心词
2. **语法练习**：so...that... 倒装结构；given 条件状语；let alone 递进否定
3. **翻译练习**：注意科学数据的翻译；倒装句的处理
4. **写作练习**：模仿科学推理的写法，论证一个科学假设

## 八、本课小结

本课探讨宇宙中是否存在外星智慧生命。核心论点：**智慧生命在宇宙中必然存在，但由于天文距离的障碍，最可行的联系方式是使用21厘米波长的无线电频率**。文章从概率推理出发，论证外星生命存在的必然性，然后分析没有访客的原因，最后提出通信方案。语法重点为 so...that... 倒装结构和 given 条件状语。