Good Riddles

Question: It cannot be seen, It cannot be felt, It cannot be heard, It cannot be smelled, It lays behind stars and under hills, and empty holes it fills. It comes first and follows after, ends life and kills laughter. What am I?

Question: A knight comes to a castle where his love is trapped. The castle is surrounded by a square moat that is 10 feet wide (it forms a square around the castle). The knight is able to fashion two 9 foot long planks to cross the moat.

How can he do this?

Question: Ants on a stick may only move left or right. If they bump into each other they bounce off of each other and immediately move in the opposite direction maintaining speed the entire time. The only time they change speed is when they fall off of the edge of the stick.

If 25 ants are randomly put on a 1 meter long stick moving 1 meter per second, what is the longest amount of time it could take for them to all fall off?

Question: You bury me when I'm alive,
and dig me up only when I die.

What am I?

Question:

What is the most common use of cowhides?