1. Beyond two or three days, the world's best weather forecasts are speculative, and beyond six or seven they are worthless.
worthless在这里的意思是没有价值的。试比较一下下面几个词的区别：
worthless adj.无用的；不值钱的
valueless adj.不足道的；毫无价值的，不值钱的
priceless adj.贵重得无法衡量价值的，无价的；极为有趣的，极为荒唐可笑的
invaluable adj.无价的，价值无法衡量的
2. 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 be guessed, since ground stations and satellites cannot see everywhere.
cannot see everywhere 部分否定
all，every，both，always等用于否定结构时不是全部被否定，而是表示其中的一部分被否定。而且英语多半将not置于谓语中。
例如：
All is not a gold that glitters.（即Not all that glitters is gold.）
闪闪发光物，未必尽黄金。
Every one cannot write novels.（即Not every one can write novels.）
不是所有的人都能写小说。
I don’t like both of the novels.（即I like only one of the two novels.）
这两本小说我不是都喜欢。
3. Soon the errors will have multiplied to the ten-foot scale, and so on up to the size of the globe.
and so on 等等，诸如此类，以此类推
You need to learn simple math; two multiplied by two equals four and so on.
你需要学些简单的算术，例如2乘2等于4这样的。
和它意思相同的短语是and so forth。
4. Precisely at noon an infinitely powerful computer takes all the data and calculates what will happen at each point at 12.01, then 12.02, then 12.03...
calculates后面是what引导的宾语从句。
