新概念入门第四册 14
[audio]http://sound.yywz123.com/tingbbs/xgnrm/xgnrmdsic/14.mp3[/audio]Lesson 14 The Butterfly Effect
Beyond two or three days, the world's best weather forecasts are speculative, and beyond six or seven they are worthless.The Butterfly Effect is the reason. (1)_______________________. Errors and uncertainties multiply, cascading upward through a chain of turbulent features, from dust devils and squalls up to continent-size eddies that only satellites can see.
The modern weather models work with a grid of points of the order of sixty miles apart, and even so, some starting data has to guessed, since ground stations and satellites cannot see everywhere. (2)_______________________. Suppose every sensor gives perfectly accurate readings of temperature, pressure, humidity, and any other quantity a meteorologist would want. Precisely at noon an infinitely powerful computer takes all the data and calculates what will happen at each point at 12.01, then 1202, then 12.03...
The computer will still be unable to predict whether Princeton, New Jersey, will have sun or rain on a day one month away. (3)_______________________. By 12.01, those fluctuations will already have created small errors one foot away. Soon the errors will have multiplied to the ten-foot scale, and so on up to the size of the globe.
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