第14课

旁白 neutral

Beyond two or three days, the world's best weather forecasts are speculative,

超过两三天，世界上最好的天气预报都是推测性的，

旁白 neutral

and beyond six or seven they are worthless.

超过六七天，它们就毫无价值了。

旁白 neutral

The Butterfly Effect is the reason.

蝴蝶效应就是原因。

旁白 neutral

For small pieces of weather--

对于局部天气——

旁白 neutral

and to a global forecaster, small can mean thunderstorms and blizzards--

对于全球预报员来说，局部可能意味着雷暴和暴风雪——

旁白 neutral

any prediction deteriorates rapidly.

任何预测都会迅速恶化。

旁白 neutral

Errors and uncertainties multiply, cascading upward through a chain of turbulent features,

误差和不确定性倍增，通过一系列湍流特征向上级联，

旁白 neutral

from dust devils and squalls up to continent-size eddies that only satellites can see.

从尘卷风和飑线直到只有卫星才能看到的洲际大小的涡流。

旁白 neutral

The modern weather models work with a grid of points of the order of sixty miles apart,

现代天气模型采用相距约六十英里的网格点，

旁白 neutral

and even so, some starting data has to be guessed,

即便如此，一些初始数据也必须是猜测的，

旁白 neutral

since ground stations and satellites cannot see everywhere.

因为地面站和卫星无法看到所有地方。

旁白 neutral

But suppose the earth could be covered with sensors spaced one foot apart,

但是假设地球可以被间隔一英尺的传感器覆盖，

旁白 neutral

rising at one-foot intervals all the way to the top of the atmosphere.

并以一英尺的间隔一直上升到大气的顶端。

旁白 neutral

Suppose every sensor gives perfectly accurate readings of temperature,

假设每个传感器都能提供完全准确的温度读数，

旁白 neutral

pressure, humidity, and any other quantity a meteorologist would want.

压力、湿度以及气象学家想要的任何其他量。

旁白 neutral

Precisely at noon an infinitely powerful computer takes all the data and calculates what will happen at each point

正午时分，一台无限强大的计算机获取所有数据，并计算出每个点将发生什么，

旁白 neutral

at 12.01, then 12.02, then 12.03...

在12点01分，然后12点02分，然后12点03分……

旁白 neutral

The computer will still be unable to predict whether Princeton, New Jersey, will have sun or rain on a day one month away.

这台计算机仍然无法预测一个月后新泽西州普林斯顿是晴天还是雨天。

旁白 neutral

At noon the spaces between the sensors will hide fluctuations that the computer will not know about,

中午时，传感器之间的空间会隐藏计算机不知道的波动，

旁白 neutral

tiny deviations from the average.

那些与平均值微小的偏差。

旁白 neutral

By 12.01, those fluctuations will already have created small errors one foot away.

到12点01分，这些波动就已经在离传感器一英尺的地方造成了小误差。

旁白 neutral

Soon the errors will have multiplied to the ten-foot scale, and so on up to the size of the globe.

很快，这些误差将倍增到十英尺的尺度，并以此类推，直到全球范围。