It's as if the whole of America

就好像整个美国

was getting bigger and bigger every day.

日益增大

You'd think it would be impossible to keep the map up to date.

你可能会认为地图永远赶不上变化

But cosmologists take everything into account,

但是宇宙学家考虑周全

by using careful measurements of the expansion rate.

将仔细测量而得的膨胀速率纳入其中

It works like the scale factor on any road map.

工作原理和公路图上的比例尺类似

Imagine the United States is doubling every day.

假设美国土地面积每天翻番

You wouldn't want to make a new map every day,

你可不会希望每天制作新地图

you wouldn't draw a new map.

太不现实了

All you would have to do really is change the legend.

你只需修改一下比例尺就行

Instead of one mile between tick marks,

一刻度现在代表1.6公里

the next day would be two miles,

第二天它就代表3.2公里

the next day would be four miles.

第三天就代表6.4公里

And that scale, changing on the side in your legend,

图例中的比例发生变化

would completely account

如实反映了

for the fact that the States kept doubling.

土地面积不断翻番的事实

And so you could keep your originally drawn map.

这样地图本身不用做任何更改

The map of the observable universe doesn't change

除了比例系数 可观测宇宙的星图

except for the scale factor.

并没有发生变化

重点解释：

1.as if 犹如，好像

例句：She ran as if the Old Boy were after her.

她跑得飞快好像魔鬼在追她似的。

2.instead of 代替；而不是 ...

例句：I gave him advice instead of money.

我给了他忠告，而不是钱。

3.except for 除 ... 之外； 要不是由于

例句：The room was empty except for a broken wood chair.

屋子里除了一张破木椅什么都没有。