Nothing
Humanity's always been uncomfortable with zero and the void. The ancient Greeks declared them unnatural and unreal. Theologians argued that God's first act was to banish the void by the act of creating the universe ex nihilo, and Middle-Ages thinkers tried to ban zero and the other Arabic "ciphers." But the emptiness is all around us — most of the universe is void. Even as we huddle around our hearths and invent stories to convince ourselves that the cosmos is warm and full and inviting, nothingness stares back at us with empty eye sockets.