英语听力：探索发现 2014-06-04 BBC 地平线：陨石的真相-10（在线收听） |
Heset out to investigate a hundred-year-old theory that said asteroids werepowered by the Sun itself. It was called the Yarkovsky effect. The Yarkovskyeffect is a very small acceleration and acts on asteroids and what it is is ifyou take a model, the Sun is hitting the asteroid, warming the surface. And asthe asteroid rotates, that hot surface radiates the heat out in a differentdirection into space and that causes an acceleration, a very slightacceleration coming from the photons that were emitted from the asteroid. The ideais that this acceleration, slight as it is, can have significant effects uponthe orbits of asteroids over millions of years. Itwas an intriguing idea. What sent asteroids out of their orbit and on a pathtowards Earth was photon propulsion. But what was lacking was proof.
TheArecibo telescope is over 300 metres in diameter. It’s one of the most powerfultelescopes in the world and it uses radar to mark the precise position ofobjects in deep space. It was this telescope that would allow Steve Chesley todetect any tiny alterations in the orbit of asteroid Golevka more than 15million kilometres out in space.
Weknew that it would be in one place if the Yarkovsky effect wasn’t acting on it,and it would be over here if it was acting and our models were correct.
WhenSteve and his team studied the data, the results were unequivocal. |
| 原文地址：http://www.tingroom.com/lesson/yytltsfx/2014/273530.html |