as it is known to all (that...) (as 做状语从句连词，是状语从句, 可以加that)
与 as is known to all (as做主语，是定语从句)
与 it is known to all that... (主语从句，it是形式主语)
As is widely known, the moon is closer to the us than the sun.(定从)
= That the moon is closer to the us than the sun is widely known.(主从)
= It is widely known that the moon is closer to the us than the sun.(主从)
As it is known to everyone, I thought you knew about it too.(状从)
They were short of sticks to make frames for the climbing vines，without which the yield would be halved.
They thanked Tom，without whose support they would not have succeeded.
These new neighbors，to whom I was introduced yesterday，have come here from Beijing.