As I’ve quipped before, everything in the Universe secretly desires to be Iron.

Why? Meet the nucleus: Protons and neutrons in an uneasy alliance. Neutrons, conveniently enough, are neutral in electrical charge. No problem rubbing two of them together. Protons, however, are positively charged. Remember, like charged objects don’t like sitting next to one another, thanks to electrostatic forces. Holds true for protons. So, how does the nucleus of an atom hold together? Nuclear force! At really short distances, this attractive force between neutrons and protons overwhelms the electrical forces trying to fling the protons apart.

Think of a nucleus as a party. The protons are like the type A, cliquish people at the party–constantly talking bad about one another when afar, but all lovey-dovey when up and close. The neutrons are the type-B’s, pretty nonpartisan about people from afar, but agreeable enough (if a bit dull) when up close. There is an optimum mix of these two kinds of people, the perfect party mixing the right number of type A’s and type B’s. Too small of a party? Boring! Too big? Unwieldy! Having too many type A’s, with too few type B’s to smooth things out? Disaster. Too many type B’s? Dull disaster. You’ve been at a bad party that suddenly got better, either by someone coming or going. The sense of relief, the release of nervous energy, is palpable.

Iron is that perfect party, combining the ideal total number along with the perfect mix of protons and neutrons.

The energy released in a nuclear reaction is the relief of a small nucleus as it gains some protons and neutrons or the relief of a huge nucleus as it splits into two smaller nuclei–in either case, getting closer to the ideal.

Every nuclear power plant in operation today works by capturing the energy release when a really unhappy large nucleus breaks up into two smaller and more successful get-togethers–atomic fissioning. When these cranky huge parties break up, a few neutrons typically get flung out at high speeds–think of these as a few type-B’s from the party screaming away in tears. If these neutrons hit another large nucleus, teetering towards breaking up already, they can smash the party to pieces, sending yet more neutrons out.

So, you can imagine a game where you place enough of these large nuclei next to one another, such that the neutrons from one breaking up shortly cause a neighboring large nucleus to break up, sending more neutrons out to break up more nuclei… creating a chain reaction.

Building a nuclear reactor is all about getting the right density of heavy, unhappy, nuclei next to one another, and successfully creating a chain reaction. The heat produced can be captured and used to boil water, and then turn a turbine creating electricity. Disco!