听力原文： In a scientific context, the word 'chaos' bas a slightly different meaning than it docs in its general usage as a state of confusion, lacking any order. Chaos, with reference to chaos theory, refers to an apparent lack of order in a system that nevertheless obeys particular laws or rules. The two main components of chaos theory are the ideas that systems—no matter how complex they may be—rely upon an underlying order, and that very simple or small systems and events can cause very complex behaviors or events. The Earth's atmosphere is a chaotic system with regularly occurring weather phenomena like wind, cloud, rain, snow, fog and dust storms and less common events(natural disasters) like tornadoes, hurricanes and ice storms, so small changes to one part can have large effects elsewhere. This makes it very difficult to accurately predict weather changes more than a few days in advance, though weather forecasters are continually working to extend this limit through the scientific study of weather, Meteorology. Chaos theory says that the slightest variation in the motion of the air will grow with time. This idea is sometimes called the butterfly effect, from the idea that the motions caused by the flapping wings of a butterfly eventually could produce marked changes in the state of the atmosphere. Because of this sensitivity to small changes it will never be possible to forecast perfectly, although there still is potential for vast improvement. (33)