Image: Britannica As the first Chinese astronaut ever sent into space in 2003, Yang Liwei made history with his ride on Shenzhou 5. However, beyond the accomplishment, what he heard during that flight was quite disturbing, a strange sound of knocking, which seemed to come from somewhere outside of the spaceship.Yang Liwei told China Daily that the knock sounded “just like someone was knocking on the shell of the spaceship. For example, when you use a hammer to knock on the shell of an iron bucket.” The sound originated not from within the ship but could not be traced.This unusual…