Why Are We Fascinated With The Unknown?

From sailors exploring uncharted waters to the viewing public avoiding spoilers for their favorite TV show, people love the unknown. But why? What is it about not knowing something that makes it interesting, and makes us want to explore or discover?

Why are we fascinated with the unknown?

Related questions: Why is it better to watch a sporting event live rather than recorded? Why is change so unsettling? How important is intuition? How do we know what we don’t know?