I’ve made it to page five hundred something of The Making of the Atomic Bomb when it finally got really good, and by “really good” I mean I got to the part that guys would like most: The part about how they got the atomic bomb to blow up.

This was not as easy as it sounds. If you have a critical mass of uranium, that means you have a lump of uranium big enough to explode simply because it’s big enough. Uranium is all over the place, common as dirt, really, but it doesn’t blow up because there’s never enough of it in one place to start a self-sustaining chain reaction.

(Also, it’s very dirty. A critical mass of uranium has to be very pure to explode, which is one of the reasons they used plutonium instead. Another good reason: Plutonium makes a bigger bang. Nuclear physics: Don’t try to pretend it’s not cool.)

A critical mass of uranium can be quite small, no bigger than a pineapple, in the almost poetic words of Enrico Fermi. The trouble is, how do you lump together that much uranium? When the lump reaches critical mass, it explodes, and you know what that looks like. So, to employ the simplest visual, you couldn’t lump it together like a mud pie; as you picked up that last handful of uranium and brought it toward the critical mass the chain reaction would begin before you came even close to slapping it into place. The radiation would kill you and anybody near you, and there might be a tiny little kaboom, but nothing like what the Los Alamos guys were hoping for.

One bright guy thought of shooting the key piece into the sub-critical mass with a cannon. That’s pretty good guy thinking, but not quite going the whole nine yards. Try again.

Yes? You in the back?

“Let’s use a couple tons of plastic explosives to crush the pieces together!”

Yes! Blow up the bomb with a bomb! I like the way this guy thinks! What’s your name, son?

“Seth Neddermeyer.”

Take a bow, Seth. You’re a real guy’s guy.