[seoguru]

The more you know, the more you know that you don't know. As you throw logs on the campfire, the perimeter of darkness grows.

[matwood]

As you throw logs on the campfire, the perimeter of darkness grows.

I like that one. I've always thought of knowledge as a sphere and what the surface of the sphere touches is the intersect of your knowledge with what you know and don't know. As your knowledge grows so the does the sphere and your awareness about what you do not know.