be known to be/do something idiom
C1 众所周知
If something or someone is known to be or do something, people know that it is true or happens, or that someone is or does something.
A daily intake of 20 mg of vitamin C is known to be sufficient in most cases to ward off scurvy. 众所周知，每天摄入20毫克维生素C就足以抵御坏血病了。