ELI5: Explain Like I'm 5

Singular homology

Okay kiddo, I'll explain singular homology in a way that is easy for you to follow.

Imagine you have a big round ball. If you cut that ball into smaller pieces, they might have different shapes, like triangles, circles, or squares. These smaller pieces are called "simplices".

Now let's say we have a shape that we want to understand better, like a donut. We can imagine drawing a bunch of lines around the donut to make it into smaller pieces, just like we did with the big ball.

We can also imagine assigning a number to each of these smaller pieces. This number tells us how many times the piece goes around the donut. For example, the central circle in the donut might have a number of 1, because it goes around the donut once. A smaller circle around the middle might have a number of 2, because it goes around the donut twice.

All of these smaller pieces and numbers together make up what is called the "chain complex".

Now, we can use this chain complex to understand more about the donut. We can imagine stretching each piece out into a line, and then "gluing" them all together. This new shape is called the "homology".

The homology tells us how many holes the shape has. In the case of the donut, it has one hole, which we can see from the central circle. So the homology of the donut is one.

By understanding the homology of a shape, we can learn more about its properties and characteristics. And that, my young friend, is what singular homology is all about!