The word googol, a one followed by a hundred zeros, was coined by a nine-year-old. The mathematician Edward Kasner asked his nephew Milton what such a number should be called, and that was the answer. The boy offered a googolplex too, which was to be a one followed by zeros until you got tired of writing them. Kasner turned it down, and his reason is the best thing in the book: people get tired at different times, and it would never do for a heavyweight boxer to be a better mathematician than Einstein just because he had more stamina. So he made it ten to the power of a googol instead, which is fair to everyone and can’t be written out by anybody. I think the boy’s version had one thing going for it. It was the only one of the two that anyone could ever finish.