ELI5: Explain Like I'm 5

Commutative ring spectrum

Alright, let's imagine you have a box of toys. Each toy represents a number. Now, a commutative ring is like a special box where you can do certain math operations with these toys.

First, let's talk about addition. You can take two toys from the box and put them together. This is like adding two numbers. But in a commutative ring, the order doesn't matter. So if you have toys A and B, you can either put A and then B together, or you can put B and then A together. The result will be the same. This is called the commutative property.

Now, let's move on to multiplication. You can also take two toys and multiply them together. This is like doing the multiplication operation with two numbers. Again, in a commutative ring, the order doesn't matter. So if you have toys A and B, you can either multiply A and then B, or you can multiply B and then A. The result will be the same. This is also called the commutative property.

But here comes the interesting part. In a commutative ring spectrum, you can not only add and multiply two toys, but you can also add and multiply more than two toys at once. Let's say you have toys A, B, and C. You can add them together by first adding A and B, and then adding the result to C. Or, you can add B and C first, and then add the result to A. The result will still be the same. This is called the associativity property.

Similarly, you can multiply three toys A, B, and C by first multiplying A and B, and then multiplying the result by C. Or, you can multiply B and C first, and then multiply the result by A. Again, the result will be the same. This is also part of the associativity property.

In addition to these operations, a commutative ring spectrum also has something called an identity element. This is like a special toy that, when added or multiplied by any other toy, doesn't change the result. It's like the number 0 in regular addition and the number 1 in regular multiplication. In a commutative ring spectrum, you always have an identity element for both addition and multiplication.

So, in summary, a commutative ring spectrum is like a special box of toys where you can add and multiply them together. The order doesn't matter for addition and multiplication, and you can add and multiply more than two toys at once. There is also an identity element that doesn't change the result when added or multiplied with other toys. It's a fun and interesting way to do math operations!