Contrary to popular belief, "falling stars" are not stars at all, but are m

游客2024-10-23 27

问题    Contrary to popular belief, "falling stars" are not stars at all, but are meteors, solid bodies that travel throng space.
   Meteor, ranging in size from that of a pinhead, to many tons, are visible to the naked eye at night, when the friction between the surfaces of the meteors and of the air, produces heat as the meteors enter the earth’s
atmosphere. The intense heat burns up the meteors, which leave a blazing trail of light in their wake.
   Most meteors do burn up when they enter the earth’s atmosphere, with the exception of the large mete- ors, which are dragged through the earth’s atmosphere by the earth’s gravitational pull. After successful landings upon the earth, these huge bodies are renamed meteorites. Some scientists theorize that thousands of meteors fall to the earth during the daytime and the nighttime, but this theory is impossible to prove or to disprove, as most would necessarily land in water, which covers most of the earth’s surface.
   Generally speaking, meteors and meteor particles travel together in swarms like bees, with the exception of the loners, and travel in any direction they choose. Nature’s spectacular fireworks show, a "meteor shower", comes into view when the swarms encounter the upper layer of the earth’s atmosphere during the earth’s perpetual revolution around the sun. The friction produced when the meteors and the meteor particles rub against the atmospheric air, and they fall towards the earth in a brilliant display of light.
   The source of meteors traveling through space has yet to be explained satisfactorily. For thousands of years, the common belief held, was that meteors, or "falling stars," were literally from out of this world. In 467 BC, Roman historians recorded the extraordinary fall of a meteor to the earth.
   Today, astronomers support the theory that comets spawn the swarms. The comets’ offspring, the mete- or swarms, travel in regular orbits, similar to the earth’s orbit around the sun. One must be quite patient to witness such a swarm, or a meteor shower, as the swarms cross the earth’s path only once every 33 years. This spectacle of light is, however, well worth the wait.  [br] Meteors were believed to be "falling stars" NOT in that ______.

选项 A、they themselves can send out light and heat
B、they look like stars
C、they are from out of the world
D、they are moving downward

答案 A

解析细节理解题。对应原文第三段：Most meteors do bum up when they enter the arth’s atmosphere， with the exception of the large meteors，which are dragged through the earth’s alzaosp here by the earth’s gravitational pull．并由第二段可知其象星星一样发光和热，所以可知正确原因是B，C，D，因此答案为A。gravitational adj．(万有)引力的；重力的

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