ELI5: Explain Like I'm 5

Infinite Ramsey theory

Have you ever played a game of hide and seek? Well, imagine playing hide and seek with your friends, but instead of hiding in plain sight, your friends can hide anywhere in the world, even in different galaxies or universes! That's what infinite Ramsey theory is kind of like, a very complicated game of hide and seek.

In infinite Ramsey theory, mathematicians are trying to find hidden patterns or groups within really enormous sets of numbers. These patterns are called "Ramsey graphs." The idea is that no matter how big or infinite a set of numbers is, you can always find certain groups of numbers that have some kind of order or pattern, like always having a certain number of odd or even numbers.

To find these hidden patterns, mathematicians use something called "Ramsey's theorem." Ramsey's theorem basically says that if you have a big enough set of numbers, you'll always be able to find some smaller group of numbers that follows a certain pattern or order. For example, if you have a set of infinite numbers, like all the numbers between 1 and infinity, you can always find a subset of that set with a certain order or pattern, like every third number being even.

Now, you might be wondering why anyone would want to play such a complicated game of hide and seek with numbers. Well, Ramsey theory has practical applications in fields like computer science and physics. For example, it can help computer scientists design algorithms that find patterns in really large sets of data. It can also help physicists understand the structure of the universe by finding patterns in the way particles interact with each other.

So, in short, infinite Ramsey theory is a way of finding hidden patterns or groups within really enormous sets of numbers, using a complicated game of hide and seek. It's used in fields like computer science and physics to help solve real-world problems.