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What are falling stars?
Contrary to popular belief, "falling stars" are not stars at all, but are meteors, solid bodies that travel through space.
Meteors, 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 incinerates 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 meteors, 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 incinerates the swarms, 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 espouse the theory that comets spawn the swarms. The comets' offspring, the meteor 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.
note:
meteor: 流星
pinhead: 针头，小东西
incinerate: 把……烧成灰烬
meteorite: 陨石
meteor shower: 流星雨
espouse: 支持，赞成
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发表于 2005-1-31 00:34
