You only need 40 digits of pi to calculate the circumference of… You only need 40 digits of pi to calculate the circumference of the observable universe to a margin of error of one hydrogen atom.Source: Unbelievable Facts Interesting Facts Related posts:Before 194 BC, using only sticks and shadows, Eratosthenes of… A man lived that was shot in the head with a .22 caliber bullet…. A man in Florida woke up with a severe headache. When he went to… Mathematician Paul Erdos could calculate in his head, given a…