She was a calutron girl.

What’s a calutron?

How much do you want to know?

I dont know. Whatever you think.

All right. To build a uranium bomb you first have to separate the U-238 found in nature from U-235. In a thousand pounds of natural uranium there’s only about seven pounds of U-235, so that’s a lot of shoveling just to get started. There are several ways of separating it—enriching it, they like to say—and the electromagnetic system isnt the best, it was just the first. The calutron was invented by E O Lawrence and it was basically a mass spectrometer and acted as the collection device for the enriched uranium. Cal was short for California. Tron is just from the Greek. A measuring scale, or maybe an instrument. The uranium was first combined with chlorine and the resulting uranium tetrachloride was then ionized and driven by a series of electromagnets around what they called the racetrack. The racetrack was over a hundred feet long and the magnets were twenty feet tall. You have to think big. Because of the war they couldnt find enough copper to make the coils for the magnets, the conductors, so they went to the US Treasury Department and borrowed fourteen thousand tons of silver and trucked that in and used it.

Borrowed.

Borrowed. They returned it after the war. The first tracks they designed, the Alpha tracks, werent all that efficient so they took the material it produced and ran it again through a new design called the Beta and it actually came out weapons grade. In reality the Beta was not all that different. It was even smaller—about half the size of the Alpha, with ten foot magnets. The calutrons themselves were inserted into the racetracks sideways and the collectors were removed periodically and emptied. Of course what made the whole system workable was that U-238 is three neutrons heavier than U-235 so that it follows a greater arc in a magnetic field.

Of course.

Jesus.

Sorry. Please continue.

You sure?

Yes. Please.

There were eventually nine huge brick buildings that housed all of this. They may still be there for all I know. They looked like enormous shoe factories. Five Alpha tracks and four Beta. Eleven hundred and fifty-two calutrons in all. They ran continually and each girl monitored a single calutron. There was no talking. The girls sat on stools in long hallways and monitored the dials and adjusted the knobs so as to keep the beamcurrent maximized. It was a slow process. The U-235 for the Little Boy bomb that leveled Hiroshima was carried to Santa Fe on the train a few pounds at a time in a briefcase by an army officer in a business suit. When they had sixty-four kilos they were good.

He wouldnt become radiated? The chap in the suit.

No.

Could you explain topology in something like that straightforward a manner?

You’re not being facetious?

No. I’m not.

I dont think so. The electromagnetic separation process is a very simple mechanical operation. You could explain it to a ten year old. Topology is about the mathematics of shapes. I could say that Poincaré’s conjecture has to do with the inherently spherical nature of shapes that appear to be otherwise. Almost. But that may not even be a good example. Particularly if the conjecture is wrong. Well. For Poincaré it wasnt even a conjecture. It was more a query.