Zero is a metaphor. It is a bridge. It is the resonant interval where all the action takes place. The Hindus developed zero from sunya, the empty space. They left an interval in which zero could resonate and carry new meanings. The zero became the unknown and allowed the development of avyaka-ganit (science of all the calculation of the unknown). Zero, as the metaphor, is bridge between the known and the unknown, between being and non-being.