Answer:
What does everyone know how to open but not how to close?
This thing all things devours: Birds, beasts, trees, flowers; Gnaws iron, bites steel; Grinds hard stones to meal; Slays king, ruins town, And beats high mountains down.
It is a path of cow juice spread across the sky but cannot be seen by the naked eye
I have five letters and people eat me. When you remove my first letter I become a crime. Remove my first two letters and I am an animal. If you remove my first and last letters I'm a form of music
What goes up but never comes down?
Before Google, we actually had to physically look things up in this building full of knowledge.