Expert: Michael Hartley - 9/3/2006

Question
Dear Mr. Hartley
When was the number 0 discovered of invented?
Thank You!

Answer
As far back as the 2nd century BC, the ancient Babylonians already used the digit 0. They didn't write it like we do, rather, they used a space, or two slashes, or (later) three hooks. However, they didn't have a concept of zero as a number - no idea that 'one less than one' had any meaning.

The ancient Greeks had a concept of zero the number, but debated whether it was a real number or not. "How can nothing be something?" the argument went. These debates continued into the middle ages. Some ancient Greeks even questioned whether 1 was a number! Nonetheless, in Ptolemy's writings, from 130AD, we find zero used as a number - its symbol is a small 'o' with a bar on top. It was used only for remainders and fractional parts however.

One or two centuries earlier, the number 0 was already being used in Mayan calendars.

The Romans used zero similarly to the Greeks, in the 6th century - only as a remainder.

The first "proper" use of the modern number zero was by an Indian mathematician, Brahmagupta, in 628AD. He even considered negative numbers, and outlined rules for how to combine negative, positive, and zero in addition, subtraction, multiplication and division. His rules are consitent with our modern understanding of zero, except for his rules on how to divide by zero. He assigned values, eg, to 0/0, but now we understand that such values cannot be properly defined without leading to all sorts of logical problems.

Hope that helps!

You can get more information from, for example, http://www-groups.dcs.st-and.ac.uk/~history/HistTopics/Zero.html