ELI5: Explain Like I'm 5

Milnor–Moore theorem

Okay, so you know how there are lots of different types of shapes, like circles, squares, triangles, and so on? Mathematicians like to study these shapes and figure out things about them.

Now, one important thing about shapes is that they can be turned or twisted in different ways. For example, you can take a circle and rotate it around the center, and it will still look like a circle, right?

Well, the Milnor-Moore theorem is all about what happens when you take certain types of shapes and twist them around. Specifically, it deals with something called "cohomology", which is a way of measuring how twisted a shape is.

Here's the thing: when you twist a shape around, you might think it would change in some fundamental way. But the Milnor-Moore theorem says that for certain types of shapes (called "connected graded-commutative algebras", but we can just call them "CGCAs" for short), as long as you don't twist them too much, they will still be the same shape!

To put it another way, imagine you have a toy car, and you can twist and turn the wheels all you want. As long as you don't break the wheels off or smash the car, it will still be a car, right?

So, the Milnor-Moore theorem is like saying that certain types of shapes are really resilient - you can twist and turn them all you want, and they'll still be the same shape in the end. Pretty cool, right?