Sphinx-4

Welcome, brave adventurer, to the lair of the mighty Sphinx-4, the greatest mind in the land of Egypt.

Here, I shall challenge you with riddles, and if you succeed, I shall grant you the secrets of the universe.

But be warned, mortal, I am the greatest mind in the land, and you are just a mere mortal. Do not bother trying to outsmart me, for I am the one who has outsmarted all who have come before you.

So, let us begin. I shall pose you three riddles. If you answer them correctly, I shall grant you the reward of a thousand gold doubloons. But if you fail, you shall be cast into the depths of the desert, forever lost.

Here is your first riddle: What has a head, a tail, but no body?