For centuries there was no number for «nothing»

It seems like the most obvious thing in the world, but zero is a surprisingly late invention.

Roman numerals have no symbol for «nothing»: that's why doing sums with them was a nightmare. The idea of zero as a number you can add and multiply with came from India —the mathematician Brahmagupta laid out its rules around the year 628— and it took centuries to make its way to Europe through the Arab world.

Without that little circle meaning «nothing», there would be no algebra, no computers, and no text like this one.