Lesson 55

Recent developments in astronomy have made it possible to detect planets in our own Milky Way and in other galaxies.
天文学领域的最近发展已经使得探测我们自己银河系以及其他星系中的行星成为可能。
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。
Finding planets is proving hard enough, but finding life on them will prove infinitely more difficult.
寻找行星已证明足够困难，但在其上寻找生命将证明更加困难。
The first question to answer is whether a planet can actually support life.
要回答的第一个问题是，一颗行星是否真的能支持生命。
In our own solar system, for example, Venus is far too hot and Mars is far too cold to support life.
例如，在我们自己的太阳系中，金星太热而火星太冷，都无法支持生命。
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，甚至在这里，动植物生命也花费了四十多亿年才进化出来。
Whether a planet can support life depends on the size and brightness of its star, that is its sun.
一颗行星是否能够支持生命取决于其恒星（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.
想象一颗比我们自己的太阳大二十倍、亮二十倍、热二十倍的恒星。
A planet would have to be a very long way from it to be capable of supporting life.
一颗行星必须离它非常遥远才能够支持生命。
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.
或者，如果恒星很小，支持生命的行星就必须绕着它在近距离轨道上运行，并且还要为生命形式的发展提供完美的条件。
But how would we find such a planet?
但是我们该如何找到这样一个行星呢？
At present, there is no telescope in existence that is capable of detecting the presence of life.
目前，现存没有任何望远镜能够探测到生命的存在。
The development of such a telescope will be one of the great astronomical projects of the twenty-first century.
这样一台望远镜的发展将是二十一世纪伟大的天文项目之一。
It is impossible to look for life on another planet using earth-based telescopes.
使用陆基望远镜在另一个星球上寻找生命是不可能的。
Our own warm atmosphere and the heat generated by the telescope would make it impossible to detect objects as small as planets.
我们自身温暖的大气层和望远镜产生的热量，将使探测像行星那样小的物体变得不可能。
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.
甚至像非常成功的哈勃望远镜那样的绕地轨道望远镜也不合适，因为我们太阳系中存在尘埃颗粒。
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.
为了寻找外太空的生命，望远镜必须远至木星，因为我们越往太阳系边缘旅行，尘埃就变得越稀薄。
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.
一旦我们探测到一颗行星，我们就必须找到一种遮挡其恒星光线的方法，以便能够正确地看到该行星并分析其大气层。
In the first instance, we would be looking for plant life, rather than little green men.
首先，我们将寻找的是植物生命，而不是小绿人。
The life forms most likely to develop on a planet would be bacteria.
在行星上最有可能进化的生命形式将会是细菌。
It is bacteria that have generated the oxygen we breathe on earth.
正是细菌产生了我们在地球上呼吸的氧气。
For most of the earth's history they have been the only form of life on our planet.
在地球历史的大部分时间里，它们一直是这个星球上唯一的生命形式。
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，我们总是怀有希望，即我们将被小绿人访问，并且我们将能够与他们交流。
But this hope is always in the realms of science fiction.
但这种希望始终处于科幻小说的范畴。
If we were able to discover lowly forms of life like bacteria on another planet, it would completely change our view of ourselves.
如果我们能够在另一个星球上发现像细菌一样的低级生命形式，那将彻底改变我们对自己的看法。
As Daniel Goldin of NASA observed, Finding life elsewhere would change everything.
正如美国国家航空航天局的丹尼尔·戈尔丁所观察到的，在别处寻找生命将会改变一切。
No human endeavour or thought would be unchanged by it.
没有任何人类的努力或思想会因它而不发生改变。