Which was a revolution. From Megan Gannon at LiveScience:
The concept of zero as a number was revolutionary in mathematics. Historians have long known the idea came from India, but its exact origins remain murky.
Now, the oldest Indian reference to the digit zero has been identified, in a manuscript dating back to the third or fourth century, scientists at the University of Oxford in England announced.
The concept of zero as the number representing absolute nothingness paved the way for algebra, calculus and computer science. The first text to discuss zero in the numerical sense is the Indian astronomer Brahmagupta’s work “Brahmasphutasiddhanta,” which was written in A.D. 628.More.
Zero is an abstraction, not a number (it corresponds to nothing), which makes its role all the more interesting…
See also: Is zero even?