December 19th: Uranium-235
Christmas can be described as a time of year where there is great deal of anticipation and work towards it. Then when it's finally arrived, it requires a lot of work to keep it under control, because if you don't keep an eye on it then it will get out of hand, and possibly cause devastating carnage in the brief space of time where it occurs.
Also, the presents. There's usually one thing you want. Possibly two. There are many things you'd like, but few things you actively want. And sometimes you get them, or you get something that gives more than you were expecting. That's always nice
Encapsulating both of these things is uranium-235, an isotope of Uranium that is the one we use to generate nuclear power. Uranium-235 has an odd atomic structure that means the nucleus can be split relatively easily, by the addition of another neutron. This releases a lot of energy, as there is a net loss of mass when the nucleus splits. This mass becomes energy.
Thing is, when the uranium-235 nucleus splits, it releases neutrons. These could feasibly hit another atomic nucleus and cause it to split, releasing energy and more neutrons, which could feasibly and so on and so on.
In the enriched form of Uranium, there pretty much always another atom within neutron-spitting distance, hence the chain reaction used to give us nuclear power, or nuclear weaponry.
Bright lights, followed by uncontrolled carnage. Isn't that just like Christmas?