How it began
Britannica states that the modern zero, a numeral with its own value and arithmetic rules, originated in ancient India. In the 7th century the astronomer Brahmagupta became the first known scholar to treat zero, called shunya in Sanskrit, as a number in its own right. His Brahmasphutasiddhanta, written in 628, is the first text to discuss the arithmetic of zero, including division by zero. A temple inscription at Gwalior, dated 876, was long the oldest known example of a zero symbol in India. An older dot placeholder appears in the Bakhshali manuscript, which was unearthed in 1881 in what is now Pakistan.
Before it existed
Placeholder symbols for an empty position are much older than zero as a number. Sumerians in Mesopotamia were the first to represent the concept, about 5,000 years ago, and the ancient Maya independently used a placeholder zero. These marks showed the absence of a digit in a given place but were not numbers that could be added, subtracted or multiplied. In the Bakhshali manuscript a dot served the same purpose.
How it works
In a place-value system the position of a digit sets its value, so a symbol is needed to show that a position is empty. Brahmagupta went further and gave rules for calculating with zero itself as a quantity. Combined with the nine other digits, it produced a positional system based on 10 symbols, 1 to 9 and 0, in which any number can be written and computed with.
How it spread
Between the 8th and 9th centuries the Persian mathematician al-Khwarizmi studied Indian mathematical texts, including the works of Brahmagupta. He described the positional system of ten symbols and credited its origins to Indian scholars, which helped introduce the numerals to the Islamic world. By the 9th century zero appeared in Arabic texts in a form derived from Indian notation, resembling the modern oval symbol. The numerals reached Europe through the writings of Middle Eastern mathematicians about the 12th century.
What lasted
Zero made possible the zero-to-nine decimal system on which algebra developed in 9th century Persia. Marcus du Sautoy of the University of Oxford called the emergence of zero as a number in its own right one of the great moments in the history of mathematics. Researchers quoted by National Geographic caution that evidence is thin and that exactly where and how zero moved from a placeholder to a number used in equations is still debated.
