英语听力：探索发现 2014-07-11 BBC 地平线：陨石的真相-26

 Tim has developed a map to visualize¹ their location. And on that map, the most important are the Near-Earth asteroids³, the ones closest to the planet. On the screen here is a map of the solar system. 

 

And I’ve got the Sun in the centre and the third planet out here would be that of the Earth. The red dots in here are actually Near-Earth asteroids. The green ones are the regular Main-Belt asteroids. 

 

There are over 9,000 Near-Earth asteroids. But there’s one type that’re particularly concerned to locate, those asteroids that are over one kilometer in diameter. An Earth impact with one of these would spell disaster. Tim’s data reveals that there are 900 asteroids bigger than a kilometer in those dangerous Near-Earth orbits. But he has some good news.

 

Right now, there’s no information that any of those large objects will hit the Earth in the next 100 years. So we’re safe from impact of those objects for at least 100 years. So there are no catastrophic asteroid² impacts on the horizon. But there are still dangers out there. 

1 visualize   

vt.使看得见，使具体化，想象，设想

参考例句：

• I remember meeting the man before but I can't visualize him.我记得以前见过那个人，但他的样子我想不起来了。
• She couldn't visualize flying through space.她无法想像在太空中飞行的景象。

2 asteroid   

n.小行星；海盘车(动物)

参考例句：

• Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
• It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。

3 asteroids   

n.小行星( asteroid的名词复数 )；海盘车，海星

参考例句：

• Asteroids,also known as "minor planets",are numerous in the outer space. 小行星，亦称为“小型行星”，在外太空中不计其数。
• Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。