Long Riddles and Answers

Question: Two men were on a ship. They were both facing opposite directions, one facing east and the other facing west. But, they were both seeing each other. *WITHOUT MIRRORS* How is this possible?

Question: My thickness is no more than a few centimeters, yet my depth can span to infinity. Although mundane, I intimidate most animals. When in my presence, you will inevitably follow me. What am I?

Question: Six glasses are in a row. The first three are filled with milk and the last three are empty. By moving only one glass, can you arrange them so that the full and the empty glasses alternate?

Question: It dances and skips,
it's read in the eyes but it cheats with the hips,
If it meets its match it's easily caught,
but it's worth nothing if it is bought.
What is it?

Question: My boots can fit though the green glass doors but my shoes cannot. Sea weed can fit but algae cannot. A tree can fit but a forest cannot. The moon can fit but a feather cannot. Why is this?