《新概念英语》（美音）III-55

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

Listen to the tape then answer the question below.

Which life forms are most likely to develope on a distant planet?

Recent developments in astronomy have made it possible to detect planets in our

own Millky Way and in other galaxies.This is a major 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 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 lief on another planet using earth-based telescope. 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 of the

dust particles in our solar system. A telescope would have to be as far away as the

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 detect 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 analves 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 becteria. 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-dwellers, 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 scientic 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 n.天文学 particle n.微粒，粒子

relative adj.相对的 Jupiter n.木星

infinitely adv.无限地，无穷地 blot v.遮暗

solar adj.太阳系的 analyse v.分析

Venus n.金星 bacteria n.细菌

Mars n.火星 oxygen n.氧气

orbit n.运行轨道 realm n.领域

astronomical adj.天文学的 endeavour n.努力

generate 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.......，一颗行星能否支持生命取决于....

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。