There probably aren’t many pages in the annals of human achievement dedicated to donkey traders. But perhaps there should be: without them, we would not have calculus. Or physics. Or computers. Or a great deal of other important things, all of which require something that, for most human history, simply didn’t exist: the number zero. Unlike positive numbers, which have around for aeons, zero only reared its head 5000 years ago, in Mesopotamia, when the Sumerians started trading donkeys and sheep and chickens in such massive numbers that their primitive counting system began to buckle. They need a new way of doing maths to help them keep track of things: one that would let them count higher than anyone had before. What they settled on was positional notation: a system where any number, no matter how big, could be written using combinations of just a few symbols, in columns that go up by factors of 10. Simply move one column to the left, and all of a sudden its 10 times larger. This is the same counting system we use today. Traders quickly realised they needed a way to signal when there was nothing in a certain column. That’s when some plucky scribe decided to draw two semi circles, or brackets, on their clay tablet to stand for ‘nothing here’. Over time these brackets smudged into a solid circle, which became the modern 0 we use today. But as zero entered the world, the world decided it could do without. The ancient Greeks, who appropriated heavily from Mesopotamian culture, decided not to take zero with them. They were too snooty to adopt an idea that came from something as base as commerce. Moreover, they were scared of zero. It represented the chaotic nothingness from which they thought the world arose, and to which they were worried it might return. So they ignored it That could have been it for zero, but luckily the Indians discovered it on their own some time around AD 400. Unlike the Greeks, hindus were totally at peace with the concept of nothingness. The void was something they actively sought out, so a number representing nothing wasn’t a metaphysical problem. They added it to their other nine numerals, and picked up where the Sumerians left off, doing complex arithmetic left, right and centre. From there zero headed west. The Arab world welcome it with open arms – perhaps the ‘nothingness’ of the desert had primed them for the concept – and used it to create calculations known as algorithms. It was here that a Sicilian traveller named Leonardo Fibonacci encountered zero, along with the other nine Arabic numerals. He took them back to Europe in 1202, where Italy’s merchants instantly saw how useful zero was in balancing their ledger. P.S. Europe actually resisted: the Catholic Church decried zero as ‘dangerous Saracen magic’, and demanded the faithful continue using their cumbersome Roman numerals.