問題詳情

(43-46)Now, suppose you want to predict the weather. Then, youneed two basic types of information: (1) the current weatherand (2) how weather changes from one moment to the next.You could attempt to predict the weather by creating a “modelworld.” For example, you could overlay a globe of the Earthwith graph paper and then specify the current temperature,pressure, cloud cover, and wind within each square. These areyour starting points, or initial conditions. Next, you couldinput all the initial conditions into a computer, along with aset of equations (physical laws) that describe the processesthat can change weather from one moment to the next.Suppose the initial conditions represent the weatheraround the Earth at this very moment and you run yourcomputer model to predict the weather for the next month inNew York City. The model might tell you that tomorrow willbe warm and sunny, with cooling during the next week and amajor storm passing through a month from now. But supposeyou run the model again, making one minor change in theinitial conditions, say, a small change in the wind speedsomewhere over Brazil. This slightly different initialcondition will not change the weather prediction for tomorrowin New York City. But for next month’s weather, the twopredictions may not agree at all!The disagreement between the two predictions arisesbecause the laws governing weather can cause very tinychanges in initial conditions to be greatly magnified over time.This extreme sensitivity to initial conditions is sometimescalled the butterfly effect: If initial conditions change by asmuch as the flap of a butterfly’s wings, the resultingprediction may be very different.The butterfly effect is a hallmark of chaotic systems.Simple systems are described by linear equations in which,for example, increasing a cause produces a proportionalincrease in an effect. In contrast, chaotic systems aredescribed by nonlinear equations, which allow for subtler andmore intricate interactions. For example, the economy isnonlinear because a rise in interest rates does notautomatically produce a corresponding change in consumerspending. Weather is nonlinear because a change in the windspeed in one location does not automatically produce acorresponding change in another location.Despite the name, chaotic systems are not necessarilyrandom. In fact, many chaotic systems have a kind ofunderlying order that explains the general features of theirbehavior even while details at any particular moment remainunpredictable. In a sense, many chaotic systems— like theweather— are “predictably unpredictable.” Our understandingof chaotic systems is increasing at a tremendous rate, butmuch remains to be learned about them.
43. According to the passage, it will be difficult to predictweather  _____________
(A) without more powerful computers.
(B) because we don’t communicate globally.
(C) unless we learn more about chaotic systems.
(D) until we understand the physical laws of atoms.

參考答案

答案：C
難度：簡單0.722222
統計：A(0),B(4),C(13),D(0),E(0)

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