1 When we look at the sky and see a bright light moving quickly across it or com

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When we look at the sky and see a bright light movingquickly across it or coming towards the earth, we talk about seeing a “shootingstar” or a “falling star”. These moving lights are not, in fact, stars at all.They are small pieces of matter from outer space, which burn up as they enterthe Earth’s atmosphere. The correct name of them is meteoroids. Any pieces thatmake it to the Earth’s surface without completely burning up are known asmeteorites. A meteor is actually the name given to the light we see when ameteoroid is burning up.

When a meteorite hits the Earth at speeds between 11 and 72kilometers a second, it can do amazing damage. A very large meteorite couldknock the earth out of its orbit. If this happened, all life on Earth wouldprobably become extinct（灭绝）. The path we follow around the Sun would changeand as a result the Earth would become either much hotter or much colder. Thischange in temperature would affect sea levels and the amount of water inrivers. There would either be huge floods, which would cover most of the landwith water, or the oceans would dry up and there would be a drought, whichmeans a long period of time without rain. Either way, nothing could survive. Ifa large meteorite landed in the sea it would almost certainly cause tsunamis,which would race towards the land, destroying everything in their paths.

Although it is unlikely the Earth will be struck by ameteorite large enough to do that kind of damage, there is evidence of fairlylarge meteorites hitting the Earth in the past. In 1908 a large area of forest in Tunguska, Siberia was destroyed by a meteorite that came apart just before it hit the ground. Themoon, however, has about three billion craters陨石坑caused bymeteorites impacting影响 its surface. The reason more meteorites havereached the surface of the moon than the surface of the Earth is that the moondoes not have enough atmosphere for the meteorites to burn up in. some of themeteorites that have reached the Earth’s surface have done considerable damage.Some scientists believe it was a change of climate caused by meteorites hittingthe Earth that resulted in the extinction of the dinosaurs and other largeprehistoric animals.

Scientists are especially interested in meteorites becausethey contain information about the solar system. It is widely believed byscientists that most meteorites are produced by collisions（碰撞） between asteroids (small planets). These collisionsprobably happened many billions of years ago. This means the physical andchemical structure of a meteorite can give scientists information about theearly days of the universe.

【小题1】          The story is about___.     

A. floods caused by meteors

B. matter from outer space

C. life on Earth millions of years ago

D. meteorites that have damaged the moon

【小题2】          The Earth has___.                    

A. three billion craters

B. fewer craters than the moon

C. more craters than the moon

D. a thinner atmosphere than the moon

【小题3】          Some scientists believe thedinosaurs became extinct because ___.     

A. they were hit by meteors

B. meteorites landed on their nests

C. meteorites landed and changed the climate

D. they could no longer breathe the atmosphere

【小题4】          Meteors are___.                                         

A. small planets

B. the same as asteroids

C. from broken parts of asteroids

D. the light we see when meteoroids hit our atmosphere

试题答案

【答案】

【小题1】          B

【小题2】          B

【小题3】          C

【小题4】          D

【解析】

试题