Lesson 55 From the earth:Greetings 来自地球的问候

Listen to the tape then answer the question below.
听录音，然后回答以下问题。
Which life forms are most likely to develop on a distant planet?

    英式发音：

    美式发音：

Recent developments in astronomy have made it possible todetect planets in our own Milky Way and in other galaxies. This is amajor achievement because, in relative terms, planets are very small and do not emit light. Finding planets is proving hard enough, but finding life on them will prove infinitely more difficult. The first question to answer is whether a planet can actually support life. In our own solar system, for example, Venus is far too hot and Mars is far too cold to support life. Only the Earth provides ideal conditions, and even here it has taken more than four billion years for plant and animal life to evolve.

Whether a planet can support life depends on the size and brightness of its star, that is its 'sun'. Imagine a star up to twenty times larger, brighter and hotter than our own sun. A planet would have to be a very long way from it to be capable of supporting life. Alternatively, if the star were small, the life supporting planet would have to have a close orbit round it and also provide the perfect conditions for life forms to develop. But how would we find such a planet? At present, there is no telescope in existence that is capable of detecting the presence of life. The development of such a telescope will be one of the great astronomical projects of the twenty-first century.

It is impossible to look for life on another planet using earth-based telescopes. Our own warm atmosphere and the heat generated by the telescope would make it impossible to detect objects as small as planets. Even a telescope in orbit round the earth, like the very successful Hubble telescope, would not be suitable because ofthe dust particles in our solar system. A telescope would have to be as faraway asthe planet Jupiter to look for life in outer space, because the dust becomes thinner the further we travel towards the outer edges of our own solar system. Once we detected a planet, we would have to find a way of blotting out the light from its star, so that we would be able to 'see' the planet properly and analyse its atmosphere. In the first instance, we would be looking for plant life, rather than'little green men'. The life forms most likely to develop on a planet would be bacteria. It is bacteria that have generated the oxygen we breathe on earth. For most of the earth's history they have been the only form of life on our planet. As Earth wellers, we always cherish the hope that we will be visited by little green men and that we will be able to communicate with them. But this hope is always in the realms of science fiction. If we were able to discover lowly forms of life like bacteria on another planet, it would completely change our view of ourselves. As Daniel Goldin of NASA observed, 'Finding life elsewhere would change everything. No human endeavour or thought would be unchanged by it. '

New Words and Expressions 生词和短语

astronomy（1. 1）/ə'strɔnəmi/n．天文学
particle（1. 20）/'pa:tikəl/n．微粒，粒子
relative（1. 3）/'relətiv/adj．相对的
Jupiter（1. 20）/'dʒu:pitə/n．木星
infinitely（1. 5）/'infinitli/adv．无限地，无穷地
blot（1. 22）/blɔt/v．遮暗
solar（1. 7）/'səulə/adj．太阳系的
analyse（1. 23）/'ænəlaiz/v．分析
Venus（1. 7）/'vi:nəs/n．金星
bacteria（1. 25）/bæk'tiəriə/n．细菌
Mars（1. 7）/ma:z/n．火星
oxygen（1. 25）/'ɔksidʒən/n．氧气
orbit（1. 13）/'ɔ:bit/n．运行轨道
realm（1. 28）/relm/n．领域
astronomical（1. 15）/'æstrə'nɔmikəl/adj．天文学的
endeavour（1. 30）/in'devə/n．努力
generate（1. 18）/'dʒenəreit/v．产生

Notes on the text 课文注释

1 Milky Way，银河。
2 Whether a planet can support life depends on…，一颗行星是否能支持生命取决于……。在这句话中，以whether引导的名词性从句作句子的主语。
3 up to，直到。
4 earth-based telescopes，放置在地球上的望远镜。
5 in the realms of science fiction，在科幻小说中存在。
6 NASA，这是国家航空和宇宙航空局的首字母缩写（也可作N．A．S．A．或Nasa）。这个组织建于1958年，负责组织美国的航空宇航研究。它的巨大成功之一便是1969年7月21日把一个人（内尔·阿姆斯特朗，乘“阿波罗11”号宇宙飞船）送上了月球。

参考译文

天文学方面的最新发展使得我们能够在银河系和其他星系发现行星。这是一个重要的成就，因为相对来说，行星很小，而且也不发光。寻找行星证明相当困难，但是要在行星上发现生命会变得无比艰难。第一个需要解答的问题是一颗行星是否有能够维持生命的条件。举例来说，在我们的太阳系里，对于生命来说，金星的温度太高，而火星的温度则太低。只有地球提供了理想的条件，而即使在这里，植物和动物的进化也用了40亿年的时间。

一颗行星是否能够维持生命取决于它的恒星——即它的“太阳”——的大小和亮度。设想一下，一颗恒星比我们的太阳还要大，还要亮，还要热20倍，那么一颗行星为了维持生命就要离它的恒星非常远。反之，如果恒星很小，维持生命的行星就要在离恒星很近的轨道上运行，而且要有极好的条件才能使生命得以发展。但是，我们如何才能找到这样一颗行星呢？现在，没有一台现存的望远镜可以发现生命的存在。而开发这样一台望远镜将会是21世纪天文学的一个重要的研究课题。

使用放置在地球上的望远镜是无法观察到其他行星上的生命的。地球周围温暖的大气层和望远镜散出的热量使得我们根本不可能找到比行星更小的物体。即使是一台放置在围绕地球的轨道上的望远镜——如非常成功的哈勃望远镜——也因为太阳系中的尘埃微粒而无法胜任。望远镜要放置在木星那样遥远的行星上才有可能在外层空间搜寻生命，因为我们越是接近太阳系的边缘，尘埃就越稀薄。一旦我们找到这样一颗行星，我们就要想办法将它的恒星射过来的光线遮暗，这样我们就能彻底“看见”这颗行星，并分析它的大气层。首先我们要寻找植物，而不是那种“小绿人”。在行星上最容易生存下来的是细菌。正是细菌生产出我们在地球上呼吸的氧气。在地球发展的大部分进程中，细菌是地球上唯一的生命形式。作为地球上的居民，我们总存有这样的希望：小绿人来拜访我们，而我们可以和他们交流。但是，这种希望总是只在科幻小说中存在。如果我们能够在另一颗行星上找到诸如细菌那种低等生命，那么这个发现将彻底改变我们对我们自已的看法。正如美国国家航空和宇宙航空局的丹尼尔·戈尔丁指出的：“在其他地方发现生命会改变一切。任何人类的努力和想法都会发生变化。”

　　自学导读
Notes on the text
课文注释
1  Without it we could not make a living．没有它我们就无法生存下去。without it 起非真实条件句的作用，make
a living，谋生。
2  hard by …，在……近旁。
3  in a heat wave，在大热天。
4  stand to lose，处于损失的境况之中。
5  put…out of order，使……出故障。
6  Noah's ark，诺亚方舟。这是摘自《圣经·旧约》《创世纪》中的典故。诺亚是故事中上帝用洪水消灭人类后的新始祖；诺亚借助一方形大船，与他家属及每种动物雌雄各一逃脱了洪水之灾。

　　Multiple choice questions
多项选择题
Choose the correct answers to the following questions. Unit 3  Lesson 56
Comprehension 理解
1  People whose property was less favourably situated than the writer's ______ .
a．had no means of pumping water away from the river
b．farmed land which for the most part lay on a level with the river banks
c．lived where the climate was more variable and the rainfall heavier
d．had land which lay upstream where the river current was stronger
2  The writer's family suspected that their nearest neighbours might have trouble managing ______ .
a．as their farm was liable to flooding and they had not lived there long
b．because the floods had put the telephone out of order
c．when they saw the river sweep over the boundary between the two farms
d．as soon as they saw a dead sheep floating down the river
3  When the writer's family saw a raft appear along the river, they ______ .
a．thought their neighbour's house must have been submerged
b．rowed their boats down to the bank and pulled the raft in with the oars
c．managed to get down to the river in time to save their neighbours
d．were surprised that their neighbours had been able to save themselves
Structure 结构
4  ______ is only enough to supply the needs of the house. (11. 3-4)
a．Water of the spring
b．The water in spring
c．The water from the spring
d．Spring water
5  We have parties at the boathouse, built in the meadow ______ (11. 9-10)
a．at the farm by a predecessor of ours
b．for us at the farm by a predecessor
c．by our predecessor at the farm
d．by one of our predecessors at the farm
6  After it ______ for a long time, the river may overflow its banks. (1. 14)
a．is raining
b．rained
c．has rained
d．had rained
7  The strength of the current would prevent ______ anywhere before it…(1. 24)
a．that it landed
b．it from landing
c．it to land
d．the landing of it
Vocabulary 词汇
8  We ______ the seasons by the riverside…(1. 11)
a．greet
b．go out to greet
c．celebrate the arrival of
d．invoke the start of
9  We were, however, ______ our nearest neighbours…(1. 19)
a．concerned for
b．occupied with
c．agitated by
d．distressed about
10  ---- and ______ we took turns in watching that point. (1. 22)
a．in the peak of condition
b．in place of the most severe critic
c．at the most dangerous boundary
d．when the flood was at its height
11  ---- and pull it towards our bank before the current carried it ______ … (11. 28-29)
a．out
b．in
c．off
d．under
12  ______ we think it a miracle that they were able to do so. (11. 29-30)
a．To this day
b．Up till now
c．As yet
d．Even so