Eli5 How do you create a ruler without a ruler?

Question

How do you create a thing which is straight, when you don’t have a thing which is straight to create it with?

In: 4

Answer 1

I think the thing to remember is that practically nothing springs into being out of the blue. It evolves.

So there’s no telling where or how it started – certainly someone might notice he could see in a straight line, but it was hard to draw a straight line in the dirt or whatever. And then someone asks, “What’s the big deal? Why do we need something perfectly straight? Maybe you could stop fuckin’ around and help me kill this buffalo.”

And it goes from there.