Did you know that the number zero was discovered by Hindu mathematicians around the sixth century? For many centuries the notion of number "zero" was disregarded as nonsense.
Sure, people had the idea of a number that stands for nothing, but they were confused by it. Why, Aristotle himself argued that the idea of zero should be outlawed, because when you try to divide other numbers by zero you don't get anywhere. Zero times infinity is still zero!
Older cultures like the Babylonians used a marker of some sort to designate the space where no number goes, such as what comes between six and nine in the number six hundred and nine. The Greeks even used a round figure similar to the modern zero.
It wasn't until the Indian mathematicians got a hold of zero that people started thinking of it as a number that could be used as more than a place-holder for other numbers. It sounds weird, but that was a major step forward in mathematics!