ELI5: Explain Like I'm 5

Smooth projective plane

Okay, imagine you're playing with some Play-Doh. You can roll it out and it lays flat on the table, right? Now imagine you're making a little house out of the Play-Doh. You would eventually need to make some walls, a roof, and maybe even windows or a door. But what if you wanted to make a Play-Doh house that was shaped like a ball or a globe? That's where a smooth projective plane comes in.

So, a smooth projective plane is like a big ball made out of Play-Doh that has some rules about how it works. It's a special kind of geometry that helps us understand shapes that aren't flat like a piece of paper. Instead, it is a curved surface that extends infinitely in all directions.

The "smooth" part means that everything on the surface of the ball is very nice and evenly curved - there are no sharp edges or corners. This makes it easier to do math and geometry on the surface. And the "projective" part means that we can stretch and move shapes around on the surface of the ball in special ways.

One of the cool things about a smooth projective plane is that there are no parallel lines - that means that any two lines on the surface of the ball will eventually intersect. This is different than what we're used to in our normal, flat geometry.

So, if you ever want to make a Play-Doh house that's shaped like a ball or a globe, you can use the rules of a smooth projective plane to figure out how to make it work!