距离2012年12月四六级考试越来越近,现在正是四六级考生复习冲刺的黄金时期。为了助大家取得好成绩,在线四六级频道为考生网罗了四六级辅导名师,整合了各题型备考资料,给你一站式学习体验。
Unit 2
Passage One
Unless we spend money to spot and prevent asteroids now, one might crash into Earth and destroy life as we know it, say some scientists.
Asteroids are bigger versions of the meteoroids that race across the night sky. Most orbit the sun far from Earth and don t threaten us. But there are also thousands of asteroids whose orbits put them on a collision course with Earth.
Buy $50 million worth of new telescopes right now. Then spend $10 million a year for the next 25 years to locate most of the space rocks. By the time we spot a fatal one, the scientists say, we ll have a way to change its course.
Some scientists favor pushing asteroids off course with nuclear weapons. But the cost wouldn t be cheap.
Is it worth it?Two things experts consider when judging any risk re:1)How likely the event is;and 2)How bad the consequences if the event occurs. Experts think an asteroid big enough to destroy lots of life might strike Earth once every 500, 000 years. Sounds pretty rare but if one did fall, it would be the end of the world. If we don t take care of these big asteroids, they ll take care of us, says one scientist. It s that simple.
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