英语听力：探索发现 2014-05-30 BBC 地平线：陨石的真相-9（在线收听） |
It’sremarkable how we are able to build up this picture of what’s going on millionsof miles away in the solar system. It’s one of the joys of science really, justalmost like a detective picking up on those tiny clues to tell a bigger story. Sothat the big question, the one that really needs answering, is why do some ofthese asteroids suddenly head straight towards us? Over95% of asteroids are found in an orbit between Jupiter and Mars called the mainbelt. It’s almost 200 million kilometres across and home to millions of theseorbiting rocks. And these asteroids have been following the same path formillions of years. So long as they remain here, they pose no threat to Earth. Butoccasionally, one goes astray.
Collisionsare one of the reasons why this might happen. But in the last decade, we’velearned that just a few rays of light are enough because one scientist hastracked the orbit of just one of these millions of rocks.
SteveChesley of NASA’s Jet Propulsion Lab in California has made a study of a 200million-ton asteroid called Golevka.
Thisis a model of Golevka. It’s actually about 500 metres across, say the size of afootball stadium. It rotates in this direction. As you can see, it has a veryangular shape to it. |
| 原文地址：http://www.tingroom.com/lesson/yytltsfx/2014/273525.html |