第55课

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Recent developments in astronomy have made it possible to detect planets in our own Milky Way and in other galaxies.

天文学的最新发展使得在我们自己的银河系和其他星系中探测行星成为可能。

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This is a major achievement because, in relative terms, planets are very small and do not emit light.

这是一个重大成就，因为相对而言，行星非常小且不发光。

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Finding planets is proving hard enough, but finding life on them will prove infinitely more difficult.

发现行星已经够难了，但在行星上发现生命将是无限困难的。

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The first question to answer is whether a planet can actually support life.

首先要回答的问题是，一个行星是否真的能够支持生命。

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In our own solar system, for example, Venus is far to hot and Mars is far too cold to support life.

例如，在我们自己的太阳系中，金星太热，火星太冷，都无法支持生命。

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Only the Earth provides ideal conditions, and even here it has taken more than four billion years for plant and animal life to evolve.

只有地球提供了理想的条件，即使在这里，植物和动物生命也用了超过40亿年才得以进化。

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Whether a planet can support life depends on the size and brightness of its star, that is its 'sun'.

行星是否能支持生命取决于其恒星，也就是它的“太阳”的大小和亮度。

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Imagine a star up to twenty times larger, brighter and hotter than our own sun.

想象一颗比我们自己的太阳大20倍、亮20倍、热20倍的恒星。

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A planet would have to be a very long way from it to be capable of supporting life.

一个行星必须离它非常遥远才能支持生命。

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Alternatively, if the star were small,

另一方面，如果恒星很小，

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the life-supporting planet would have to have a close orbit round it and also provide the perfect conditions for life forms to develop.

支持生命的行星就必须围绕它近距离运行，并且提供生命形式发展的完美条件。

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But how would we find such a planet?

但是我们如何才能找到这样一个行星呢？

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At present, there is no telescope in existence that is capable of detecting the presence of life.

目前，还没有任何望远镜能够探测到生命的存在。

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The development of such a telescope will be one of the great astronomical projects of the 21st century.

这种望远镜的开发将是21世纪伟大的天文学项目之一。

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It is impossible to look for life on another planet using earth-based telescopes.

使用基于地球的望远镜来寻找其他行星上的生命是不可能的。

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Our own warm atmosphere and the heat generated by the telescope

我们温暖的大气层和望远镜产生的热量

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would make it impossible to detect objects as small as planets.

将使我们不可能探测到像行星一样小的物体。

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Even a telescope in orbit round the earth, like the very successful Hubble telescope,

即使是像非常成功的哈勃望远镜那样围绕地球轨道运行的望远镜，

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would not be suitable because of the dust particles in our solar system.

也不会适用，因为我们太阳系中有尘埃颗粒。

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A telescope would have to be as far away as the planet Jupiter to look for life in outer space,

望远镜必须远达木星才能在外太空寻找生命，

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because the dust becomes thinner the further we travel towards the outer edges of our own solar system.

因为我们越往太阳系外围移动，尘埃就越稀薄。

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Once we detected a planet, we would have to find a way of blotting out the light from its star,

一旦我们探测到一颗行星，我们就必须找到一种方法来遮挡其恒星的光线，

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so that we would be able to 'see' the planet properly and analyse its atmosphere.

这样我们才能清楚地“看清”这颗行星并分析其大气层。

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In the first instance, we would be looking for plant life, rather than 'little green men'.

首先，我们将寻找植物生命，而不是“小绿人”。

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The life forms most likely to develop on a planet would be bacteria.

最有可能在行星上发展的生命形式将是细菌。

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It is bacteria that have generated the oxygen we breathe on earth.

是细菌产生了我们地球上呼吸的氧气。

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For most of the earth's history they have been the only form of life on our planet.

在地球的大部分历史中，它们一直是地球上唯一的生命形式。

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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.

作为地球居民，我们总是怀着这样的希望：我们会受到小绿人的拜访，并能与他们交流。

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But this hope is always in the realms of science fiction.

但这种希望始终停留在科幻小说的范畴。

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If we were able to discover lowly forms of life like bacteria on another planet, it would completely change our view of ourselves.

如果我们能在另一个行星上发现像细菌这样低级的生命形式，它将彻底改变我们对自身的看法。

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As Daniel Goldin of NASA observed, 'Finding life elsewhere would change everything.

正如美国宇航局的丹尼尔·戈尔丁所观察到的，“在别处发现生命将改变一切。

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No human endeavour or thought would be unchanged by it.'

任何人类的努力或思想都不会因此而保持不变。”