Miscellaneous quizzes.

There are 100 coins scattered in a dark room. 90 have heads facing up and 10 have tails up. You cannot distinguish (by feel, etc.) which coins are which. How do you sort the coins into two piles that contain the same number of tails?

"Cannot be seen, cannot be felt, cannot be heard, cannot be felt. It lies behind the stars and beneath the hills. Ends life and kills laughter. What is it?"
"In a tunnel of darkness lies a beast of iron. It can only attack when pulled back. What is it?"

 Spoiler

1. Put 50 in each pile.
2. Darkness?
3. A gun.