ELI5: Explain Like I'm 5

Inversion transformation

Imagine you have a toy car that you can move in any direction you want. Now, imagine that you want to turn your toy car upside down, so the wheels are in the air and the roof is on the ground. This is called an inversion transformation.

In math, we use a special kind of toy car called a "point" to do inversions. A point is just a dot on a piece of paper, and it can be moved around like your toy car. In an inversion transformation, we take a point and flip it over a line or a circle, like flipping your toy car over. The line or circle is called the "inversion center."

When we invert a point, we measure the distance from the point to the inversion center, and then we make that distance into a fraction (a number like 1/2 or 1/3). This fraction is called the "inversion factor." Next, we divide the distance by the inversion factor. This gives us a new distance from the inversion center to the inverted point. We use this new distance to place the inverted point.

So, imagine you have a point on a piece of paper called "A." The inversion center is a circle with radius 2. If A is right on the circle, it stays in the same place. But if A is inside the circle, we flip it over to the other side of the circle, and the distance from A to the circle becomes larger. If A is outside the circle, we flip it inside the circle, and the distance from A to the circle becomes smaller.

Inversion transformations are important in math because they help us understand how shapes and lines change when we move them around. We can use inversions to solve problems in geometry and physics, and even to create special kinds of maps and graphs. So while it might seem silly to flip your toy car upside down, in math it can lead to some very interesting and useful discoveries!