I heard her before I saw her. It was an approaching mumbling from behind as I waited on my bike at Damen and Addison.

The mumbling would break into words – I heard “Your Metra” and “With” at different points. But I didn’t turn around only because I didn’t realize she was talking to me.

Then there she was.

The woman was short and she was heavy, but not unpleasantly so. She was Latina and wore a summery green frock. She smoked a cigarette the whole time she talked.

“I didn’t know your name was Arrow Smith,” she said, happy she had gotten my attention. “You feel me, Little John?”

She laughed at her confusing joke (which, in retrospect, could also have been about Aerosmith and Lil’ Jon). Was she a solvable problem?

Years ago, I read a novel about math. It was pretty good.

In “Uncle Petros and Goldbach’s Conjecture,” an old-timey mathematician is trying to prove one of those horrible unsolved problems that are true, but no one can prove why. Goldbach’s Conjecture is a real thing a guy came up with in 1742 that says every even integer is the sum of two primes.

Like six is the sum of three and three. Or 946 is the sum of 137 and 809 and also of 347 and 599 (and 1,019 and -73, if you want to get technical).

So Goldbach’s Conjecture is true – they’ve tested it up to around 4,000,000,000,000,000,000 and never found an even number it didn’t work for.

It works, but no one knows why.

Anyway, back to the lady with the cigarette.

“I’m trying to go to a Mexican restaurant. I want to get the Mexican pizza they have where they put the cheese on top,” she said, grinding her flat palms together to mime rubbing cheese into tortilla.

Her cigarette was still clenched between the fore and middle fingers of the tortilla.

“A flau- a flu- a flautida- flautilla,” she said, a frustrated look crossing her face.

She was dressed too nicely to be a crazy homeless person. She didn’t smell like booze, although that remains the most likely option. It could be pills. Or friendliness.

In the book, which was written by a former math major, the narrator’s uncle was a mathematician in the 1930s working on a proof of Goldbach’s Conjecture. The uncle was the typical solo crazed genius type, happily puttering along trying to solve this unsolved problem until Kurt Gödel came along.

If you had a hard time with the Goldbach thing, this part is going to suck.

Gödel, who was real, proved in 1931 that every system has things in it that are true, but can’t be proven. Think about that. He proved that there are unprovable things.

So there are some things that are unsolved because they’re unsolvable, just can’t be proved. And then there are some equally complicated and silly math things that are unsolved just because no one has gotten around to solving them yet.

And then Gödel proved you can never tell which is which.

“There are gorditas and then there are fla- flautillas,” the woman said, I think meaning “flautas.”

The light turned green. I didn’t ride off, which I think surprised her as much as it did me.

So let’s go back to our fictional 1930s Greek mathematician, devoting his life in crazed style to the adding up prime numbers thing from the 1700s.

He didn’t know if he was about to be the guy who broke through 200 years of man v. math stalemate or if he was just wasting his life trying to solve a riddle that had no answer.

“They have them all over the place on the South Side,” she said, sweeping her arm in that direction down Damen. “There’s a Mexican place on Belmont that has them.”

“Yeah,” I said, noncommittally, not so much adding a thought as filling a weird silence.

She glared at me, the sunny eccentric in the pretty green frock suddenly turning nasty.

“’Yeaaaaah,’” she mocked.

I wished her luck and rode off down Damen. There are unsolvable problems and unsolved ones. But Goldbach’s Conjecture never turned nasty on a guy.

Some problems aren’t worth solving.

Buy the novel I was talking about

Or just say forget it and read about unicycles