新概念英语第三册lesson55课堂笔记

新概念英语 第三册 Lesson 55 From the Earth Greetings 来自地球的问候 （一）书本 Recent developments in astronomy have made it possible to detect planets in our own Milky Way and in other galaxies. 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。 This is a major achievement because, in relative terms, planets are very small and do not emit light. 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。 Finding planets is proving hard enough, but finding life on them will prove infinitely more difficult. 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。 The first question to answer is whether a planet can actually support life. 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。 In our own solar system, for example, Venus is far too hot and Mars is far too cold to support life. 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。 Only the Earth provides ideal conditions, and even here it has taken more than four billion years for plant and animal life to evolve. 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。 Whether a planet can support life depends on the size and brightness of its star, that is its sun . 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。 Imagine a star up to twenty times larger, brighter and hotter than our own sun. 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， A planet would have to be a very long way from it to be capable of supporting life. 那么一颗行星为了维持生命就要离开的它的恒星非常远。 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. 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， But how would we find such a planet? 但是，我们如何才能找到这样一颗行星呢? At present, there is no telescope in existence that is capable of detecting the presence of life. 现在，没有一台现存的望远镜可以发现生命的存在。 The development of such a telescope will be one of the great astronomical projects of the twenty-first century. 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。 It is impossible to look for life on another planet using earth-based telescopes. 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。 Our own warm atmosphere an