Everything that does not exist in the universe is represented by the number ZERO. In some weird way you could say they DO exist in the universe but the exact number of them is zero.
This number of things that don't exist is an infinite number.
Sometimes I like to imagine all the impossible things that I wish could exist but are I know are impossible, and think they DO exist as the number zero. All our impossible fantasies and even our what we dream of exist in this universe but are represented by the numeral zero. Zero represents nothingness and when surrounded by nothingness (sensory deprivation) we begin to dream of things.
Perhaps, nothing is exactly what dreams are made from.