Just How Many Digits of Pi Do We Need?

CoolScienceFacts.Com has a short article about efforts to determine ever more digits of Pi (which has been calculated to more than a trillion digits).

As CoolScienceFacts notes, however, there aren’t a lot of practical reasons to determine Pi very far beyond 40 digits,

Based on all this effort, you might assume that it’d be useful to know a trillion digits of pi. However, if you had a circle the size of the observable universe, and you wanted to compute its circumference with an accuracy equal to the size of a proton, the number of digits of pi that you’d need is only 43.

Either mathematicians are totally crazy, or they’re planning ahead for a time when the survival of humanity will depend on the ability to construct extremely large, accurate circles.