Two men are walking the woods. They come across a large hole the ground, several meters across and apparently bottomless. After examining the hole for a moment, they decide to throw something into the hole to see how long it takes for it to hit the bottom. The first man throws in a pebble, and after a long pause hears nothing. The second man throws in stone, and again nothing. The work together to roll a small boulder into the hole. They wait for a few minutes, but again, nothing. Finally, the f…