o 'see' the planet properly and analyze 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-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 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 endeavor or thought would be unchanged by it."

new words and expressions 生词和短语

astronomy

n. 天文学

relative

adj. 相对的

infinitely

adv. 无限地，无穷地

solar

adj. 太阳系的

venus

n. 金星

mars

n. 火星

orbit

n. 运行轨道

astronomical

adj. 天文学的

generate

v. 产生

particle

n. 微粒，粒子

jupiter

n. 木星

blot

v. 遮暗

analyse

v. 分析

bacteria

n. 细菌

oxygen

n. 氧气

realm

n. 领域

endeavour

v. 努力

参考译文

天文学方面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开的它的恒星非常远。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”。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。在地球上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的那种低等生命，那么这个发现将彻底改变我们对我们自己的看法。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。”

lesson 47

our neighbour, the river

河流，我们的邻居

listen to the tape then answer the question below.

听录音，然后回答以下问题。

why had the neighbours left their farm?

the river which forms the eastern boundary of our farm has always played an important part in our lives. without it we could not make a living. there is only enough spring water to supply the needs of the houses, so we have to pump from the river for farm use. we tell river all our secrets. we know instinctively, just as beekeepers with their bees, that misfortune might overtake us if the important events of our lives were not related to it.

we have special river birthday parties in the summer. sometimes were go upstream to a favourite backwater, sometimes we have our party at the boathouse, which a predecessor of ours at the farm built in the meadow hard by the deepest pool for swimming and diving. in a heat wave we choose a midnight birthday party and that is the most exciting of all. we welcome the seasons by the riverside, crowning the youngest girl with flowers in the spring, holding a summer festival on midsummer eve, giving thanks for the harvest in the autumn, and throwing a holy wreath into the current in the winter.

after a long period of rain the river may overflow its banks. this is a rare occurrence as our climate seldom guest to extremes. we are lucky in that only the lower fields, which make up a very small proportion of our farm, are effected by flooding, but other farms are less favorably sited, and flooding can sometimes spell disaster for their owners.

one had winter we watched the river creep up the lower meadows. all the cattle had been moved into stalls and we stood to lose little. we were, however, worried about our nearest neighbors, whose farm was low lying and who were newcomers to the district. as the floods had put the telephone out of order, we could not find out how they were managing. from an attic window we could get a sweeping view of the river where their land joined ours, and at the most critical juncture we took turns in watching that point. the first sign of disaster was a dead sheep floating down. next came a horse, swimming bravely, but we were afraid that the strength of the current would prevent its landing anywhere before it became exhausted. suddenly a raft appeared, looking rather like noah's ark, carrying the whole family, a few hens, the dogs, cat, and bird in a cage. we realized that they must have become unduly frightened by the rising flood, for their house, which had sound foundations, would have stood stoutly even if it had been almost submerged. the men of our family waded down through our flooded meadows with boathooks, in the hope of being able to