Contrary to popular belief， “falling stars” are not stars at all， but are meteors① that solid bodies travelling through space. Meteors， ranging in size from that of a pinhead② to many tons， when the meteors enter the earth’s atmosphere， the friction between surfaces of the meteors and of the aier produces heat， so that meterors are visible to the naked eye at night. The intense heat incinerates③ the meteors which are made to 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 dragged④ 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， most meteors and meteor particles except loners travel together in swarms⑤ like bees 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. Heat produced by the friction⑥ 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 not yet been 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 espouse⑦ the theory that comets spawn the swarms. The comets’⑧ 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.
① meteorn. ［天］流星，陨星［C］
② pinheadn. 针头
③ incineratev. 烧成灰，焚化，灰化
④ dragv. 拉，拖，拖着(脚等)行进
⑤ swarmn. (密集的)一大群，一大批
⑥ frictionn. 摩擦，摩擦力［U］
⑦ espousev. 拥护，支持，信奉(主义、学说等)
⑧ cometn. ［天］彗星［C］
何为坠落的星
与人们普遍的看法相反，“坠落的星”其实根本不是“星”，而只是“流星”，是穿越太空的固态物体。流星小到细若针头，大到数吨不等。当流星进入地球大气层后，其表面与空气摩擦从而产生热量，使人们在夜间用肉眼就能看到。巨大的热量将流星焚化，使之留下一条炽热的发光的尾巴。
大多数流星在进入地球大气层时就已经被烧化了，除了一些特别大的流星，它们穿过大气层，被地心引力拖了下来。这些巨大的天体成功着陆后便被重新命名为陨石。一些科学家推断，每天每夜都有成千上万的流星坠落到地球上，但这一理论无法得到证明，也无法加以否定，因为大多数流星必然落到江河湖海中，它们占据了地球的大部分面积。
一般来说，除了极少数单独运行的，流星及流星颗粒都是成团成群运行的，就像蜂群一样，按自己选择的方向随意运行。当地球绕着太阳作循环往复的公转时，流星团如果遭遇地球大气层上层时，就会出现“流星雨”这种“大自然烟火”的壮丽景观。流星及流星颗粒与大气层摩擦产生的炽热将流星团熔化，它们纷纷向地球坠落，呈现出光芒四射、五彩缤纷的奇观。
至于穿越太空的流星的来源，还有待于得出更为满意的解答。几千年来，人们普遍认为，流星或称“坠落的星星”，实际上是天外来客。早在公元前467年，古罗马的历史学家就曾记录下流星坠落地面的不同寻常的陨落。
如今，天文学家们支持彗星产生了流星团的说法。彗星的后裔，即流星团，沿正常的轨道运行，与地球绕太阳运行的轨道相似。人们必须有足够的耐心，才能等到亲眼目睹流星团或“流星雨”发生的那一天，因为流星团穿越地球轨道每33年才有一次。可是，如果能有幸观看。