# What Makes π Special

How π shows up in a rolling wheel, a pizza, a spinning dot's wave and an endless string of digits, all built from simple circles\.

By Nadav Naor

Topic: Maths

[Open the interactive Jig](https://ask.jig.com/j/cMgtEfMGE9o4)

## Transcript

### 1. What makes π special?

Welcome to the π workshop\! π, said "pie", is the number you get when you divide the distance around a circle by the distance across it\. It is a little more than 3, and it is the same for every circle there is\.

Drag the table to look around\.

### 2. Unroll a wheel

Roll the wheel one full turn and its painted rim leaves a stripe on the ruler\. Then lay the wheel's width along that stripe\. It fits three times, with a little bit left over\. Three and a bit: that is π\.

You can also tap the wheel to roll it\.

### 3. Any size, same π

Try a tiny wheel or a giant one\. The stripe always holds three widths and the same little bit more\. That is why every turn of a bike wheel carries you forward π times its width\.

A coin, a pizza and a Ferris wheel all share the same π\.

### 4. Pizza maths

π also tells how much a circle covers\. Cut a pizza into slices and zip them together: they make a strip almost like a rectangle\. It is as tall as the radius, the distance from the middle to the crust, and π radii long\. So π tells you how much pizza you get\.

One 16\-inch pizza holds as much as four 8\-inch pizzas\.

### 5. Circles make waves

Watch the glowing dot on the spinning wheel\. As it goes round, its height draws a wave, and one full turn makes one full wave\. Sound, radio, Wi\-Fi and ocean swells are waves like this, so π shows up in all of them\.

Spin faster and the waves bunch up, like a higher note\.

### 6. Digits that never end

These towers are π's digits: 3, 1, 4, 1, 5, 9 and on\. The digits never stop and never settle into a repeating pattern\. Mathematicians call a number like that irrational\.

In 2025 a computer worked out 314 trillion digits of π\.

### 7. How much π do we need?

Build a ring using a rounded π and it will not quite close\. Add digits and watch the gap shrink about ten times with each one\. A few digits are plenty for everyday building\.

NASA steers spacecraft with just 15 decimal places of π\.

### 8. π is everywhere

Wheels, pizzas, waves, planets' orbits and even the bell curve in statistics all hide π\. Wherever there is a circle or a cycle, π is close by\. Celebrate it on Pi Day, March 14, written 3/14\.