英语听力：探索发现 2014-06-06 BBC 地平线：陨石的真相-11

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Sophotons, those elementary mass-less particles of light really can create a tinyforce. 

 

Theforce is about one ounce on Earth, say that the weight of a shot glass. That isthe force on this huge asteroid³, the size of a football stadium. Even for me itis truly remarkable⁴. It is dramatic that a force so slight can have suchdramatic changes on an individual asteroid’s orbit over millions of years.  

 

TheYarkovsky effect is subtle. It takes many millions of years to gently nudge anasteroid out of its regular orbit. But once that orbit has been disturbed, theconsequences can be profound. 

 

Nowit can come increasingly under the influence of the solar system’s largestplanet, Jupiter. Jupiter has a mass 300 times bigger than Earth’s, so there isa huge gravitational field. Often that works to our benefit. Stray objects canbe swept up in Jupiter’s gravity, drawing them into the planet. We’ve actuallyobserved Jupiter acting⁵ as a shield in this way. This photograph, from theHubble Space Telescope, shows the fragments of a comet torn apart by Jupiter’sgravity. As the pieces were drawn⁶ to the planet’s atmosphere, the impacts leftblast scars, some as big as the Earth.

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