Zero

I'm almost finished reading Zero: The Biography of a Dangerous Idea. I'll have to read it again and underline pertinent passages, because when I tried to explain zero and infinity the other night, I got myself into a terrible mess.

But, here's a bit of what I remember: Aristotle and Pythagoras were scared of zero (aka the void) and of infinity, so they refused to believe in them. To them, all numbers represented geometric shapes, so how could you have a number that had no shape? Aristotle said it was ridiculous. When Aristotle's star pupil, Alexander the Great, took over most of the world, he spread Aristotle's beliefs (which became the basis of Christianity...that's why our calendar jumps from 1 BC to 1 AD -- the monk who had to develop the calendar did not know about the number zero).

The Babylonians were the first to use zero, but only as a placeholder. (They never went into the negatives.) This sped up their calculations so much that the Greeks, who were banned from having their own zero, started using Babylonian numbers (which were base 60, incidentally, which is why we tell time using base 60) for their calculations. But then they had to convert the results back into Greek.

(In Japan, I learned that babies there are born at age one. This must stem from when they didn't believe in zero, either.)

The Indians had no problem with the concepts of void and infinity, and gladly took the Babylonians' zero and started doing algebra. They never liked geometry, so they didn't get mired in the question of how a number could exist that had no shape. The Arabs adopted Indian numbers (thus we call them Arabic numerals) and their love of the void and infinity. Islam was originally a religion that embraced the void, while Christianity hated it.

There, that's enough for now.