主句与从句之间的逗号问题

1. The moon, which is far away from the earth, creates many beautifulstories.

这句话中在creates前面用了逗号。

2. As is known to everybody, Einstein is a famous scientist.

As is known to everybody是非限定性定语从句，它放在前面，然后这句的末尾与主句之间用了一个逗号隔开。

3. Einstein, as we all know, is a famous scientist.

这句话也是在as从句后与后面的主句之间隔了一个逗号。

请教一下老师，假如从句放在句首或句中，从句末尾要与后面的主句之间用逗号隔开是吗？

然后as we all know的as的意思是？

非限制性定语从句要与主句用逗号隔开。as weall know 和第二句的 as is known to everybody 一样，在传统语法都剖析为非限制性定语从句。as指代主句内容，as从句可以坐落于句首、句末，也可以插入主句和谓语动词之间。第三句就是as从句插入句中地方。