The whole world knows it!!

Have you ever come across a piece of knowledge that you don't know, but one day find yourself needing?

You need that piece of knowledge to solve a problem. And when you look for the answer to your puzzle, you realize the answer is already common knowledge.

You find yourself asking: "Why does everybody else in the world know this, except for me? Where was I, when this common knowledge was handed out to everyone else?"

It's like learning a new word. You had know idea what it meant. You had never even heard the word used before. But once you learn that word, you hear it all the time. Everyone knows what it means.

What's with that?