ELI5: Explain Like I'm 5

Calkin algebra

Calkin algebra is like a giant toy box filled with a bunch of little toy blocks. Each block has a special trick that it can do. When you put two or more blocks together, they can do even more cool tricks!

But just like some toys are better than others, there are some blocks in the Calkin algebra that are better than others too. Those special blocks are called "invertible elements." They're like the superheroes of the toy box. When you pair them up with other blocks, they can transform them into even more powerful blocks.

To make sure everyone is playing fair in the toy box, there are some special rules that everyone has to follow. These rules are called "axioms." They tell us things like how to add and multiply the blocks, and how to make sure the invertible elements always have a friend to play with.

With all these rules in place, the Calkin algebra becomes a really cool place to play and explore. You can discover new ways to put the blocks together, and see what awesome tricks they can do. Who knows - maybe you'll even discover a new superhero block!