why Pi is important?

Question

I understand the mathematical definition of Pi, but why does it end up being used in so many formulas and applications in math, engineering, physics, etc? What does it unlock?

Edit: I understand Pi is the ratio of circumference to diameter. But why is that fact make it important and useful. For example it shows up in the equation for standard normal distribution. What does Pi have to do with a normal distribution. That’s just one example.

In: 3

Answer 1

I’d say it’s just one of the “magic numbers” of the universe like the speed of light and the golden ratio. ‘They just are’.

Edit: And just in case I missed the “ELI5” part: pi multiplied by diameter of a circle always provides the circumference of the circle.