Here's a puzzle: Put two quarters side by side so the ridges mesh like gears, then hold one still and roll the other all the way around it. How many revolutions will George Washington make?
That's a riddle from Ethan Canin's new novel, A Doubter's Almanac. The book follows Milo Andret, a troubled math genius, through three generations of his family. Canin tells NPR's Ari Shapiro about his protagonist's Michigan childhood, and the answer to the book's two quarter puzzle.
On Milo as a child deciding to make a chain out of a fallen tree
He's a kid growing up in the woods of northern Michigan — kind of a lonely kid in these lonely woods — and a giant beech tree falls over one night in a storm. And he goes out there, looks at it and gets this idea that he could whittle a chain out of the wood.
[Shapiro: And to make a chain out of a fallen tree you can't do link by link, it has to be all interlinked and you just take away everything but the chain.]
Yeah, that's exactly right. It's kind of the way Michelangelo used to sculpt and imagine everything that wasn't the Pietà. And that's what this guy does: He spends the entire summer building this unbuildable thing, whittling this unwhittlable chain. And it becomes a metaphor for what he does with the rest of his life, really, which is try to solve the unsolvable problem.
On how Milo becomes a mathematician
He turns out to have a couple of skills. One of them is that he can always tell where he is on the Earth — he has this internal compass that some people have. And later on in his life, he discovers that he can also draw very beautifully in an idiot's way — not understanding exactly what he's drawing, yet able to render everything perfectly. And those kinds of talents sort of sweep him forward into this life he didn't intend to have, which is a life as a mathematician working on one of the great unsolved problems of the century.
On mathematicians and mental illness
Mathematicians don't like it when they're associated with, you know, with mental illness. And I can see why they don't. ... A lot of mathematicians are sort of bristled when people say that they can't get along socially, that they're not good with people. But I look around the world; I think it seems to be fairly true.
On the answer to the riddle about the two quarters
Well, come on, every smart person in the world would say one — the circumference of one coin matches the circumference of the other. But it's not. It goes around twice, right? And you could prove that by taking two quarters out of your pocket. ...
That puzzle puzzles the daylights out of me. It's fantastic.