40 digits of pi
You only need 40 digits of pi to calculate the number of atoms in a circle the size of the entire universe:
Why? Consider this:
- Atoms are about 10-11 meters across
- The universe is about 90 billion light years (1027 meters) wide
Dividing it out, it takes about 1037 atoms to span the universe. So, around 40 digits of pi would be enough for an exact count of atoms needed to surround the universe. Were you planning on building something larger than the universe and precise to an atomic level? (If so, where would you put it?)
And that’s just 40 digits of precision; 80 digits covers us in case there’s a mini-universe inside each of our atoms, and 120 digits in case there’s another mini-universe inside of that one.