Lesson 55 PART A
From the earth:Greetings
Recent developments in astronomy have made it possible to detect planets in our own Millky Way and in other galaxies.(1)_______________________. 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. (2)_______________________.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.
发表于 2011-11-24 10:04
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