关于英语句子中as..as

问题描述:

关于英语句子中as..as
the discovery of electricity occured as early as about 600BC.
这里的as...as怎么理解呐
还有另外一个句子:Imagine it will keep as many songs as about 200 ordinary discs can do today!
这句子开头Imagine算是什么成分呀?

as...as 可以理解为:正如……一样,具体的意思要看中间那个词,as early as :早在……时,追溯到
这句话是祈使句,用动词原形imagine作为谓语引领整句话