Linking number

Linking number is a mathematical concept that helps us understand the number of times one rope or string is wrapped around another rope or string. Imagine you have two shoelaces of different colors. If you tie them together in a knot, a linking number can be determined based on how many times one shoelace wraps around the other shoelace.

To determine the linking number, first, you pick a point on one of the ropes, and you look at the other rope and count how many times it intersects at that point. Then you move on to the next point on the first rope, and you repeat the process. You keep doing this for every point on the first rope until you have counted all the intersections.

The linking number gives us an idea of how "tangled up" two ropes or strings are. If the linking number is zero, it means the ropes or strings are not tangled up at all. But if the linking number is more than zero, it means they are tangled and wrapped around each other.

The linking number is very useful in many fields like biology, physics, and chemistry. For example, it is used to understand the structure of DNA molecules and how they are tightly wrapped up inside our cells. Scientists also use it to study the behavior of knots in space, and to understand how different molecules interact with each other.