Number9 Open Edition

What's a (natural) number? What does it look like?

We represent numbers with symbols like 3, III,  or .

We are aware of objects that have a numeric property: Squares have 4 sides.

But, what about the number itself? What is it? What does it look like?

In 1923, John von Neumann proposed a set-theoretic construction of natural numbers: We can start with the empty set to represent 0, and then create each next object as the set containing all previous numbers. In a way, creating every natural number, a whole universe, out of "empty".

0 = {}
1 = { {} }
2 = {0, 1} = { {}, {{}} },
3 = {0, 1, 2} = { {}, {{}}, { {}, {{}} } }
...and so on.

Number9 is a creative interpretation of number 9, based on von Neumann's construction. Each closed shape is a set. Empty circles are empty sets. Think of it as 9's blueprint: An elegant, simple and easy to understand construction with fractal properties.

Number9 an open edition accessible to everyone. Let's spread an idea worth spreading beyond mathematicians.

Two/wallet = gift one to a friend. Distributed under CC0.