Ackermann set theory

Okay, so there was this guy named Wilhelm Ackermann and he was really interested in math. He wanted to create something called a set theory, which is basically just a way of organizing things.

But Ackermann's set theory was a little different than other set theories, because it was all about how sets relate to each other. He thought that sets could be used to describe different levels of infinity, which is a really big concept that a lot of adults might not even understand.

Think of it like a bunch of boxes. Each box represents a different set, and the things inside the box are all related to each other. So if you have a box with all the animals in the world, you might have a smaller box inside of it that only has birds, and another smaller box inside of that that only has parrots.

Ackermann used his set theory to try to figure out some really complicated math problems, but it's not something that a lot of people use today. It's kind of like a really old toy that some people like to play with, but most people don't even know it exists.