There was a Chinese man of the state of Qi who was worrying that the sky might one day fall down, the earth might sink, and he would not know where to hide himself. This so much troubled him that he could not eat or sleep.

Someone went to reassure him about this, saying, “the sky is only formed of bright thins in the air. There is no place where there is no air. Whenever you move or breathe, you are living right in this sky. Why would you even need ever to worry that the sky will fall down?” The man rejoined, “if the sky were really nothing but air, would not the sun, the moon and the stars fall down?” and the persuader said, “But the sun, the moon and the stars are nothing but bright things in the air. Even if they should fall down, they would not hurt anybody.” “But what if the earth should sink?” and the other replied, “The earth is also only formed of accumulated solids, which fill all space. There is no place where there are no solids. As you walk and stamp on the ground, you are moving the whole day on this earth. Why do you ever need to worry that it may be destroyed?”

Then the man was gladly relieved, so was the successful persuader. Now this allusion is used to refer to entirely unnecessary worries.