Brahmagupta · Zero
Can nothing be written as a number?
That time, that place
Bhinmal in Rajasthan. By Brahmagupta's time, India already used a system where a digit's value depends on its place. To tell 205 from 25 you need a mark saying the middle is empty — and that mark was zero.
Why this question
From here you can take one more step. What if zero is not a placeholder but a number in its own right — something you can add, subtract, and multiply like any other?
It is a strange demand. It means calculating with nothing.
What was found
He was the first to write down rules for treating zero as a number. Subtract a number from itself and you get zero. Add zero and a number is unchanged. Multiply by zero and you get zero.
He handled negative numbers formally too, explaining them as fortunes and debts: subtract a fortune from a debt and the debt grows. Division by zero stopped him, though — he wrote that zero divided by zero is zero, which is wrong.
What matters is not the individual rules but their consequence: calculation had begun to detach from the objects in front of you and run on rules of its own.
Zero was only a mark for an empty place
The rules for zero and negatives set down in the Brahmasphutasiddhanta
These rules passed through the Arab world into Europe — which took another thousand years to accept negatives as real numbers